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Chris Beams
b4fea47d5c
Introduce FeatureSpecification interface and implementations
FeatureSpecification objects decouple the configuration of
spring container features from the concern of parsing XML
namespaces, allowing for reuse in code-based configuration
(see @Feature* annotations below).
* ComponentScanSpec
* TxAnnotationDriven
* MvcAnnotationDriven
* MvcDefaultServletHandler
* MvcResources
* MvcViewControllers
Refactor associated BeanDefinitionParsers to delegate to new impls above
The following BeanDefinitionParser implementations now deal only
with the concern of XML parsing. Validation is handled by their
corresponding FeatureSpecification object. Bean definition creation
and registration is handled by their corresponding
FeatureSpecificationExecutor type.
* ComponentScanBeanDefinitionParser
* AnnotationDrivenBeanDefinitionParser (tx)
* AnnotationDrivenBeanDefinitionParser (mvc)
* DefaultServletHandlerBeanDefinitionParser
* ResourcesBeanDefinitionParser
* ViewControllerBeanDefinitionParser
Update AopNamespaceUtils to decouple from XML (DOM API)
Methods necessary for executing TxAnnotationDriven specification
(and eventually, the AspectJAutoProxy specification) have been
added that accept boolean arguments for whether to proxy
target classes and whether to expose the proxy via threadlocal.
Methods that accepted and introspected DOM Element objects still
exist but have been deprecated.
Introduce @FeatureConfiguration classes and @Feature methods
Allow for creation and configuration of FeatureSpecification objects
at the user level. A companion for @Configuration classes allowing
for completely code-driven configuration of the Spring container.
See changes in ConfigurationClassPostProcessor for implementation
details.
See Feature*Tests for usage examples.
FeatureTestSuite in .integration-tests is a JUnit test suite designed
to aggregate all BDP and Feature* related tests for a convenient way
to confirm that Feature-related changes don't break anything.
Uncomment this test and execute from Eclipse / IDEA. Due to classpath
issues, this cannot be compiled by Ant/Ivy at the command line.
Introduce @FeatureAnnotation meta-annotation and @ComponentScan impl
@FeatureAnnotation provides an alternate mechanism for creating
and executing FeatureSpecification objects. See @ComponentScan
and its corresponding ComponentScanAnnotationParser implementation
for details. See ComponentScanAnnotationIntegrationTests for usage
examples
Introduce Default[Formatting]ConversionService implementations
Allows for convenient instantiation of ConversionService objects
containing defaults appropriate for most environments. Replaces
similar support originally in ConversionServiceFactory (which is now
deprecated). This change was justified by the need to avoid use
of FactoryBeans in @Configuration classes (such as
FormattingConversionServiceFactoryBean). It is strongly preferred
that users simply instantiate and configure the objects that underlie
our FactoryBeans. In the case of the ConversionService types, the
easiest way to do this is to create Default* subtypes. This also
follows convention with the rest of the framework.
Minor updates to util classes
All in service of changes above. See diffs for self-explanatory
details.
* BeanUtils
* ObjectUtils
* ReflectionUtils
3553 lines
169 KiB
XML
3553 lines
169 KiB
XML
<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
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"http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd">
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<chapter id="mvc">
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<title>Web MVC framework</title>
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<section id="mvc-introduction">
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<title>Introduction to Spring Web MVC framework</title>
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<para>The Spring Web model-view-controller (MVC) framework is designed
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around a <classname>DispatcherServlet</classname> that dispatches requests
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to handlers, with configurable handler mappings, view resolution, locale
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and theme resolution as well as support for uploading files. The default
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handler is based on the <interfacename>@Controller</interfacename> and
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<interfacename>@RequestMapping</interfacename> annotations, offering a
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wide range of flexible handling methods. With the introduction of Spring
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3.0, the <interfacename>@Controller</interfacename> mechanism also allows
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you to create RESTful Web sites and applications, through the
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<interfacename>@PathVariable</interfacename> annotation and other
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features.</para>
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<sidebar id="mvc-open-for-extension">
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<title><quote>Open for extension...</quote></title>
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<para>A key design principle in Spring Web MVC and in Spring in general
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is the <quote><emphasis>Open for extension, closed for
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modification</emphasis></quote> principle.</para>
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<para>Some methods in the core classes of Spring Web MVC are marked
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<literal>final</literal>. As a developer you cannot override these
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methods to supply your own behavior. This has not been done arbitrarily,
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but specifically with this principal in mind.</para>
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<para>For an explanation of this principle, refer to <emphasis>Expert
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Spring Web MVC and Web Flow</emphasis> by Seth Ladd and others;
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specifically see the section "A Look At Design," on page 117 of the
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first edition. Alternatively, see</para>
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<orderedlist>
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<listitem>
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<para><ulink
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url="http://www.objectmentor.com/resources/articles/ocp.pdf">Bob
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Martin, The Open-Closed Principle (PDF)</ulink></para>
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</listitem>
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</orderedlist>
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<para>You cannot add advice to final methods when you use Spring MVC.
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For example, you cannot add advice to the
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<literal>AbstractController.setSynchronizeOnSession()</literal> method. Refer to
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<xref linkend="aop-understanding-aop-proxies" /> for more information on
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AOP proxies and why you cannot add advice to final methods.</para>
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</sidebar>
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<para>In Spring Web MVC you can use any object as a command or
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form-backing object; you do not need to implement a framework-specific
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interface or base class. Spring's data binding is highly flexible: for
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example, it treats type mismatches as validation errors that can be
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evaluated by the application, not as system errors. Thus you need not
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duplicate your business objects' properties as simple, untyped strings in
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your form objects simply to handle invalid submissions, or to convert the
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Strings properly. Instead, it is often preferable to bind directly to your
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business objects.</para>
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<para>Spring's view resolution is extremely flexible. A
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<interfacename>Controller</interfacename> implementation can even write
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directly to the response stream. Typically, a
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<classname>ModelAndView</classname> instance consists of a view name and a
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model <interfacename>Map</interfacename>, which contains bean names and
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corresponding objects such as a command or form, which contain reference
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data. View name resolution is highly configurable, through bean names, a
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properties file, or your own <interfacename>ViewResolver</interfacename>
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implementation. The model (the M in MVC) is based on the
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<interfacename>Map</interfacename> interface, which allows for the
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complete abstraction of the view technology. You can integrate directly
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JSP, Velocity, or any other rendering technology. The model
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<interfacename>Map</interfacename> is simply transformed into an
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appropriate format, such as JSP request attributes or a Velocity template
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model.</para>
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<section id="mvc-features">
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<title>Features of Spring Web MVC<!--I moved Features of Spring Web MVC before Pluggability of other MVC implementations. You want to highlight your own imp. first.--></title>
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<!--Second line of sidebar refers to JSF; don't you mean JSP? Other refs in this context are to JSP. Also note, sidebar is read-only.-->
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<xi:include href="swf-sidebar.xml"
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xmlns:xi="http://www.w3.org/2001/XInclude" />
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<para>Spring's web module includes many unique web support
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features:</para>
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<itemizedlist>
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<listitem>
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<para><emphasis>Clear separation of roles</emphasis>. Each role --
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controller, validator, command object, form object, model object,
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<classname>DispatcherServlet</classname>, handler mapping, view
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resolver, and so on -- can be fulfilled by a specialized
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object.</para>
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</listitem>
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<listitem>
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<para><emphasis>Powerful and straightforward configuration of both
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framework and application classes as JavaBeans</emphasis>. This
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configuration capability includes easy referencing across contexts,
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such as from web controllers to business objects and
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validators.</para>
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</listitem>
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<listitem>
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<para><emphasis>Adaptability, non-intrusiveness, and
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flexibility.</emphasis> Define any controller method signature you
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need, possibly using one of the parameter annotations (such as
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@RequestParam, @RequestHeader, @PathVariable, and more) for a given
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scenario.</para>
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</listitem>
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<listitem>
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<para><emphasis>Reusable business code</emphasis>,<emphasis> no need
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for duplication</emphasis>. Use existing business objects as command
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or form objects instead of mirroring them to extend a particular
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framework base class.</para>
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</listitem>
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<listitem>
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<para><emphasis>Customizable binding and validation</emphasis>. Type
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mismatches as application-level validation errors that keep the
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offending value, localized date and number binding, and so on
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instead of String-only form objects with manual parsing and
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conversion to business objects.</para>
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</listitem>
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<listitem>
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<para><emphasis>Customizable handler mapping and view
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resolution</emphasis>. Handler mapping and view resolution
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strategies range from simple URL-based configuration, to
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sophisticated, purpose-built resolution strategies. Spring is more
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flexible than web MVC frameworks that mandate a particular
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technique.</para>
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</listitem>
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<listitem>
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<para><emphasis>Flexible model transfer</emphasis>. Model transfer
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with a name/value <interfacename>Map</interfacename> supports easy
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integration with any view technology.</para>
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</listitem>
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<listitem>
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<para><emphasis>Customizable locale and theme resolution, support
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for JSPs with or without Spring tag library, support for JSTL,
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support for Velocity without the need for extra bridges, and so
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on.</emphasis></para>
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</listitem>
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<listitem>
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<para><emphasis>A simple yet powerful JSP tag library known as the
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Spring tag library that provides support for features such as data
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binding and themes</emphasis>. The custom tags allow for maximum
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flexibility in terms of markup code. For information on the tag
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library descriptor, see the appendix entitled <xref
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linkend="spring.tld" /></para>
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</listitem>
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<listitem>
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<para><emphasis>A JSP form tag library, introduced in Spring 2.0,
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that makes writing forms in JSP pages much easier.</emphasis> For
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information on the tag library descriptor, see the appendix entitled
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<xref linkend="spring-form.tld" /></para>
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</listitem>
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<listitem>
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<para><emphasis>Beans whose lifecycle is scoped to the current HTTP
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request or HTTP <interfacename>Session</interfacename>.</emphasis>
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This is not a specific feature of Spring MVC itself, but rather of
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the <interfacename>WebApplicationContext</interfacename>
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container(s) that Spring MVC uses. These bean scopes are described
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in <xref linkend="beans-factory-scopes-other" /></para>
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</listitem>
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</itemizedlist>
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</section>
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<section id="mvc-introduction-pluggability">
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<title>Pluggability of other MVC implementations</title>
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<para>Non-Spring MVC implementations are preferable for some projects.
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Many teams expect to leverage their existing investment in skills and
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tools. A large body of knowledge and experience exist for the Struts
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framework. If you can abide Struts' architectural flaws, it can be a
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viable choice for the web layer; the same applies to WebWork and other
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web MVC frameworks.</para>
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<para>If you do not want to use Spring's web MVC, but intend to leverage
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other solutions that Spring offers, you can integrate the web MVC
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framework of your choice with Spring easily. Simply start up a Spring
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root application context through its
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<classname>ContextLoaderListener</classname>, and access it through
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its<!--Identify *its*. do you mean root application context's?-->
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<interfacename>ServletContext</interfacename> attribute (or Spring's
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respective helper method) from within a Struts or WebWork action. No
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"plug-ins" are involved, so no dedicated integration is necessary. From
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the web layer's point of view, you simply use Spring as a library, with
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the root application context instance as the entry point.</para>
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<para>Your registered beans and Spring's services can be at your
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fingertips even without Spring's Web MVC. Spring does not compete with
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Struts or WebWork in this scenario. It simply addresses the many areas
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that the pure web MVC frameworks do not, from bean configuration to data
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access and transaction handling. So you can enrich your application with
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a Spring middle tier and/or data access tier, even if you just want to
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use, for example, the transaction abstraction with JDBC or
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Hibernate.</para>
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</section>
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</section>
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<section id="mvc-servlet">
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<title>The <classname>DispatcherServlet</classname></title>
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<para>Spring's web MVC framework is, like many other web MVC frameworks,
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request-driven, designed around a central servlet that dispatches requests
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to controllers and offers other functionality that facilitates the
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development of web applications. Spring's
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<classname>DispatcherServlet</classname> however, does more than just
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that. It is completely integrated with the Spring IoC container and as
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such allows you to use every other feature that Spring has.</para>
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<para>The request processing workflow of the Spring Web MVC
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<classname>DispatcherServlet</classname> is illustrated in the following
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diagram. The pattern-savvy reader will recognize that the
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<classname>DispatcherServlet</classname> is an expression of the
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<quote>Front Controller</quote> design pattern (this is a pattern that
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Spring Web MVC shares with many other leading web frameworks).</para>
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<para><mediaobject>
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<imageobject role="fo">
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<imagedata align="center" fileref="images/mvc.png" format="PNG" />
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</imageobject>
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<imageobject role="html">
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<imagedata align="center" fileref="images/mvc.png" format="PNG" />
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</imageobject>
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<caption><para>The requesting processing workflow in Spring Web MVC
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(high level)</para></caption>
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</mediaobject></para>
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<para>The <classname>DispatcherServlet</classname> is an actual
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<interfacename>Servlet</interfacename> (it inherits from the
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<classname>HttpServlet</classname> base class), and as such is declared in
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the <literal>web.xml</literal> of your web application. You need to map
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requests that you want the <classname>DispatcherServlet</classname> to
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handle, by using a URL mapping in the same <literal>web.xml</literal>
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file. This is standard J2EE servlet configuration; the following example
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shows such a <classname>DispatcherServlet</classname> declaration and
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mapping:</para>
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<programlisting language="xml"><web-app>
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<servlet>
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<servlet-name>example</servlet-name>
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<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
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<load-on-startup>1</load-on-startup>
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</servlet>
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<servlet-mapping>
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<servlet-name>example</servlet-name>
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<url-pattern>*.form</url-pattern>
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</servlet-mapping>
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</web-app></programlisting>
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<para>In the preceding example, all requests ending with
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<literal>.form</literal> will be handled by the <literal>example</literal>
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<classname>DispatcherServlet</classname>. This is only the first step in
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setting up Spring Web MVC. <!--The discussion below is a little vague about what you're doing, when you do it, and what you're accomplishing. --><!-- Is the next step shown in the next example screen?-->You
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now need to configure the various beans used by the Spring Web MVC
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framework (over and above the <classname>DispatcherServlet</classname>
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itself).<!--See previous sentence.Add info to indicate where you find info that tells you how to configure beans for MVC framework. --><!--Next paragraph, so what are you telling them to *do* here? --></para>
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<para>As detailed in <xref linkend="context-introduction" />,
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<interfacename>ApplicationContext</interfacename> instances in Spring can
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be scoped. In the Web MVC framework, each
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<classname>DispatcherServlet</classname> has its own
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<interfacename>WebApplicationContext</interfacename>, which inherits all
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the beans already defined in the root
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<interfacename>WebApplicationContext</interfacename>. These inherited
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beans can be overridden in the servlet-specific scope, and you can define
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new scope-specific beans local to a given servlet instance.</para>
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<para><mediaobject>
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<imageobject role="fo">
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<imagedata align="center" fileref="images/mvc-contexts.gif"
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format="GIF" />
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</imageobject>
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<imageobject role="html">
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<imagedata align="center" fileref="images/mvc-contexts.gif"
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format="GIF" />
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</imageobject>
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<caption>Context hierarchy in Spring Web MVC</caption>
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</mediaobject></para>
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<para>Upon initialization of a <classname>DispatcherServlet</classname>,
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the framework <!--Spring MVC or Spring Framework?--><emphasis><emphasis>looks
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for a file named</emphasis>
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<literal>[servlet-name]-servlet.xml</literal></emphasis> in the
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<literal>WEB-INF</literal> directory of your web application and creates
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the beans defined there, overriding the definitions of any beans defined
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with the same name in the global scope.</para>
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<para>Consider the following <classname>DispatcherServlet</classname>
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servlet configuration (in the <literal>web.xml</literal> file):</para>
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<programlisting language="xml"><web-app>
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<servlet>
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<servlet-name><emphasis role="bold">golfing</emphasis></servlet-name>
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<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
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<load-on-startup>1</load-on-startup>
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</servlet>
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<servlet-mapping>
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<servlet-name><emphasis role="bold">golfing</emphasis></servlet-name>
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<url-pattern>/golfing/*</url-pattern>
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</servlet-mapping>
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</web-app></programlisting>
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<para>With the above servlet configuration in place, <!--Is this something you need to do (in above example)? -->you
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will need to have a file called <literal>/WEB-INF/</literal><emphasis
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role="bold">golfing</emphasis><literal>-servlet.xml</literal> in your
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application; this file will contain all of your Spring Web MVC-specific
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components (beans). You can change the exact location of this
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configuration file through a servlet initialization parameter (see below
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for details).</para>
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<!--See *where* for details? Give x-ref to section talks about how to change the location of the file through servlet init. param.-->
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<para>The <interfacename>WebApplicationContext</interfacename> is an
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extension of the plain <interfacename>ApplicationContext</interfacename>
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that has some extra features necessary for web applications. It differs
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from a normal <interfacename>ApplicationContext</interfacename> in that it
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is capable of resolving themes (see <xref linkend="mvc-themeresolver" />),
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and that it knows which servlet it is associated with (by having a link to
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the <interfacename>ServletContext</interfacename>). The
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<interfacename>WebApplicationContext</interfacename> is bound in the
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<interfacename>ServletContext</interfacename>, and by using static methods
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on the <classname>RequestContextUtils</classname> class you can always
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look up the <interfacename>WebApplicationContext</interfacename> if you
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need access to it.</para>
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<para>The Spring <classname>DispatcherServlet</classname> uses special
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beans to process requests and render the appropriate views. These beans
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are part of Spring Framework. You can configure them in the
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<interfacename>WebApplicationContext</interfacename>, just as you
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configure any other bean. However, for most beans, sensible defaults are
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provided so you initially do not need to configure them. <!--Which beans have defaults? What do you mean you *initially* don't need to configure them? What determines whether you need to and --><!--when, if not *initially*? In table below, indicate which are defaults, which have to be configured.-->These
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beans are described in the following table.</para>
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<table id="mvc-webappctx-special-beans-tbl">
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<title>Special beans in the
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<interfacename>WebApplicationContext</interfacename></title>
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<tgroup cols="2">
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<colspec colname="c1" colwidth="1*" />
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<colspec colname="c2" colwidth="4*" />
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<thead>
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<row>
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<entry>Bean type</entry>
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<entry>Explanation</entry>
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</row>
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</thead>
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<tbody>
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<row>
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<entry><link linkend="mvc-controller">controllers</link></entry>
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<entry>Form the <literal>C</literal> part of the MVC.<!--Need info about controller function as with others in this list.Reader knows what C stands for.--></entry>
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</row>
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<row>
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<entry><link linkend="mvc-handlermapping">handler
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mappings</link></entry>
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<entry>Handle the execution of a list of pre-processors and
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post-processors and controllers that will be executed if they
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match certain criteria (for example, a matching URL specified with
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the controller).</entry>
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</row>
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<row>
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<entry><link linkend="mvc-viewresolver">view
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resolvers</link></entry>
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<entry>Resolves view names to views.<!--If it's capable of resolving, just say *resolves*. Like above, handler mappings are capable of handling the execution, but you just say *handle the execution*--></entry>
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</row>
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<row>
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<entry><link linkend="mvc-localeresolver">locale
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resolver</link></entry>
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<entry>A <link linkend="mvc-localeresolver">locale resolver</link>
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is a component capable of resolving the locale a client is using,
|
|
in order to be able to offer internationalized views</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry>Theme resolver</entry>
|
|
|
|
<entry>A <link linkend="mvc-themeresolver">theme resolver</link>
|
|
is capable of resolving themes your web application can use, for
|
|
example, to offer personalized layouts</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry>multipart file resolver</entry>
|
|
|
|
<entry>Contains functionality to process file uploads from HTML
|
|
forms.<!--Here and next one, why not just say processes file uploads, maps executions instead of *contains functionality to*?--></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><link linkend="mvc-exceptionhandlers">handler exception
|
|
resolvers</link></entry>
|
|
|
|
<entry>Contains functionality to map exceptions to views or
|
|
implement other more complex exception handling code.</entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>After you set up a <classname>DispatcherServlet</classname>, and a
|
|
request comes in for that specific
|
|
<classname>DispatcherServlet</classname>, the
|
|
<classname>DispatcherServlet</classname> starts processing the request as
|
|
follows:</para>
|
|
|
|
<orderedlist>
|
|
<listitem>
|
|
<para>The <interfacename>WebApplicationContext</interfacename> is
|
|
searched for and bound in the request as an attribute that the
|
|
controller and other elements in the process can use. <!--Use to do *what*? Also revise to indicate *what* searches for the WebApplicationContext -->It
|
|
is bound by default under the key
|
|
<literal>DispatcherServlet.WEB_APPLICATION_CONTEXT_ATTRIBUTE</literal>.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>The locale resolver is bound to the request to enable elements
|
|
in the process to resolve the locale to use when processing the
|
|
request (rendering the view, preparing data, and so on). If you do not
|
|
need locale resolving, you do not need it.</para>
|
|
<!--Reword 'if you don't need local resolving, you dont need to use it '. Are you saying locale resolving is optional? If you don't configure it, will this step occur?-->
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>The theme resolver is bound to the request to let elements such
|
|
as views determine which theme to use. If you do not use themes, you
|
|
can ignore it.</para>
|
|
|
|
<!-- MLP perhaps say that there are not side effect to this binding.etc... Clarify *ignore it*. Does this step still occur if you don't use themes? -->
|
|
|
|
<!--And what if you DO use themes, what do you do and when? Same question re locale resolving.-->
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>If you specify a multipart file resolver, the request is
|
|
inspected for multiparts; if multiparts are found, the request is
|
|
wrapped in a <classname>MultipartHttpServletRequest</classname> for
|
|
further processing by other elements in the process. (See <xref
|
|
linkend="mvc-multipart-resolver" /> for further information about
|
|
multipart handling).</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>An appropriate handler is searched for. If a handler is found,
|
|
the execution chain associated with the handler (preprocessors,
|
|
postprocessors, and controllers) is executed in order to prepare a
|
|
model or rendering.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>If a model is returned, the view is rendered. If no model is
|
|
returned, (may be due to a preprocessor or postprocessor intercepting
|
|
the request, perhaps for security reasons), no view is rendered,
|
|
because the request could already have been fulfilled.</para>
|
|
|
|
<!--fulfilled how and by what?-->
|
|
</listitem>
|
|
</orderedlist>
|
|
|
|
<para>Handler exception resolvers that are declared in the
|
|
<interfacename>WebApplicationContext</interfacename> pick up exceptions
|
|
that are thrown during processing of the request. Using these exception
|
|
resolvers allows you to define custom behaviors to address
|
|
exceptions.</para>
|
|
|
|
<para>The Spring <classname>DispatcherServlet</classname> also supports
|
|
the return of the <emphasis>last-modification-date</emphasis>, as
|
|
specified by the Servlet API. The process of determining the last
|
|
modification date for a specific request is straightforward: the
|
|
<classname>DispatcherServlet</classname> looks up an appropriate handler
|
|
mapping and tests whether the handler that is found implements the
|
|
<emphasis><interfacename>LastModified</interfacename></emphasis>
|
|
interface. If so, the value of the <literal>long
|
|
getLastModified(request)</literal> method of the
|
|
<interfacename>LastModified</interfacename> interface is returned to the
|
|
client.</para>
|
|
|
|
<para>You can customize individual
|
|
<classname>DispatcherServlet</classname> instances by adding servlet
|
|
initialization parameters (<literal>init-param</literal> elements) to the
|
|
servlet declaration in the <literal>web.xml</literal> file. See the
|
|
following table for the list of supported parameters.</para>
|
|
|
|
<!--Reword above sentence to specify whether configuring parameters in table configures last-modification-date, or are they further -->
|
|
<!--customization for some other purpose? If so, need to explain how you config last-modification-date-->
|
|
|
|
<table id="mvc-disp-servlet-init-params-tbl">
|
|
<title><classname>DispatcherServlet</classname> initialization
|
|
parameters</title>
|
|
|
|
<tgroup cols="2">
|
|
<colspec colname="c1" colwidth="1*" />
|
|
|
|
<colspec colname="c2" colwidth="4*" />
|
|
|
|
<thead>
|
|
<row>
|
|
<entry>Parameter</entry>
|
|
|
|
<entry>Explanation</entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry><literal>contextClass</literal></entry>
|
|
|
|
<entry>Class that implements
|
|
<interfacename>WebApplicationContext</interfacename>, which
|
|
instantiates the context used by this servlet. By default, the
|
|
<classname>XmlWebApplicationContext</classname> is used.</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><literal>contextConfigLocation</literal></entry>
|
|
|
|
<entry>String that is passed to the context instance (specified by
|
|
<literal>contextClass</literal>) to indicate where context(s) can
|
|
be found. The string consists potentially of multiple strings
|
|
(using a comma as a delimiter) to support multiple contexts. In
|
|
case of multiple context locations with beans that are defined
|
|
twice, the latest location takes precedence.</entry>
|
|
<!-- MLP review -->
|
|
</row>
|
|
|
|
<row>
|
|
<entry><literal>namespace</literal></entry>
|
|
|
|
<entry>Namespace of the
|
|
<interfacename>WebApplicationContext</interfacename>. Defaults to
|
|
<literal>[servlet-name]-servlet</literal>.</entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
</section>
|
|
|
|
<section id="mvc-controller">
|
|
<title>Implementing Controllers</title>
|
|
|
|
<para>Controllers provide access to the application behavior that you
|
|
typically define through a service interface. <!--I changed preceding to active voice because next sentence refers to user input. Thus *you* do some defining.-->Controllers
|
|
interpret user input and transform it into a model that is represented to
|
|
the user by the view. Spring implements a controller in a very abstract
|
|
way, which enables you to create a wide variety of controllers.</para>
|
|
|
|
<para>Spring 2.5 introduced an annotation-based programming model for MVC
|
|
controllers that uses annotations such as
|
|
<interfacename>@RequestMapping</interfacename>,
|
|
<interfacename>@RequestParam</interfacename>,
|
|
<interfacename>@ModelAttribute</interfacename>, and so on. This annotation
|
|
support is available for both Servlet MVC and Portlet MVC. Controllers
|
|
implemented in this style do not have to extend specific base classes or
|
|
implement specific interfaces. Furthermore, they do not usually have
|
|
direct dependencies on Servlet or Portlet APIs, although you can easily
|
|
configure access to Servlet or Portlet facilities.</para>
|
|
|
|
<tip>
|
|
<para>Available in the <link linkend="new-in-3-samples">samples repository</link>,
|
|
the <emphasis>PetClinic</emphasis> web application leverages
|
|
the annotation support described in this section, in the context of
|
|
simple form processing.</para>
|
|
|
|
<!-- MLP Note removed reference to imagedb -->
|
|
</tip>
|
|
|
|
<!--You need an intro sentence here that indicates the *purpose* of the following code. -->
|
|
|
|
<programlisting language="java">@Controller
|
|
public class HelloWorldController {
|
|
|
|
@RequestMapping("/helloWorld")
|
|
public ModelAndView helloWorld() {
|
|
ModelAndView mav = new ModelAndView();
|
|
mav.setViewName("helloWorld");
|
|
mav.addObject("message", "Hello World!");
|
|
return mav;
|
|
}
|
|
}</programlisting>
|
|
|
|
<para>As you can see, the <interfacename>@Controller</interfacename> and
|
|
<interfacename>@RequestMapping</interfacename> annotations allow flexible
|
|
method names and signatures. In this particular example the method has no
|
|
parameters and returns a <classname>ModelAndView</classname>, but various
|
|
other (and better) strategies exist, <!--strategies for doing *what*? -->as
|
|
are explained later in this section. <classname>ModelAndView</classname>,
|
|
<interfacename>@Controller</interfacename>, and
|
|
<interfacename>@RequestMapping</interfacename> form the basis for the
|
|
Spring MVC implementation. This section documents these annotations and
|
|
how they are most commonly used in a Servlet environment.</para>
|
|
|
|
<section id="mvc-ann-controller">
|
|
<title>Defining a controller with
|
|
<interfacename>@Controller</interfacename></title>
|
|
|
|
<para>The <interfacename>@Controller</interfacename> annotation
|
|
indicates that a particular class serves the role of a
|
|
<emphasis>controller</emphasis>. Spring does not require you to extend
|
|
any controller base class or reference the Servlet API. However, you can
|
|
still reference Servlet-specific features if you need to.</para>
|
|
|
|
<para>The <interfacename>@Controller</interfacename> annotation acts as
|
|
a stereotype for the annotated class, indicating its role. The
|
|
dispatcher scans such annotated classes for mapped methods and detects
|
|
<interfacename>@RequestMapping</interfacename> annotations (see the next
|
|
section).</para>
|
|
|
|
<para>You can define annotated controller beans explicitly, using a
|
|
standard Spring bean definition in the dispatcher's context. However,
|
|
the <interfacename>@Controller</interfacename> stereotype also allows
|
|
for autodetection, aligned with Spring general support for detecting
|
|
component classes in the classpath and auto-registering bean definitions
|
|
for them.</para>
|
|
<!-- MLP Bev.changed to 'also supports autodetection -->
|
|
<para>To enable autodetection of such annotated controllers, you add
|
|
component scanning to your configuration. Use the
|
|
<emphasis>spring-context</emphasis> schema as shown in the following XML
|
|
snippet:</para>
|
|
|
|
<programlisting language="xml"><?xml version="1.0" encoding="UTF-8"?>
|
|
<beans xmlns="http://www.springframework.org/schema/beans"
|
|
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
|
|
xmlns:p="http://www.springframework.org/schema/p"
|
|
xmlns:context="http://www.springframework.org/schema/context"
|
|
xsi:schemaLocation="
|
|
http://www.springframework.org/schema/beans
|
|
http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
|
|
http://www.springframework.org/schema/context
|
|
http://www.springframework.org/schema/context/spring-context-3.0.xsd">
|
|
|
|
<context:component-scan base-package="org.springframework.samples.petclinic.web"/>
|
|
|
|
<lineannotation>// ...</lineannotation>
|
|
|
|
</beans></programlisting>
|
|
|
|
</section>
|
|
|
|
<section id="mvc-ann-requestmapping">
|
|
<title>Mapping requests with
|
|
<interfacename>@RequestMapping</interfacename></title>
|
|
|
|
<para>You use the <interfacename>@RequestMapping</interfacename>
|
|
annotation to map URLs such as <filename>/appointments</filename> onto
|
|
an entire class or a particular handler method. Typically the
|
|
class-level annotation maps a specific request path (or path pattern)
|
|
onto a form controller, with additional method-level annotations
|
|
narrowing the primary mapping for a specific HTTP method request method
|
|
("GET"/"POST") or specific HTTP request parameters.</para>
|
|
|
|
<para>The following example shows a controller in a Spring MVC
|
|
application that uses this annotation:</para>
|
|
|
|
<programlisting language="java">@Controller
|
|
<emphasis role="bold">@RequestMapping("/appointments")</emphasis>
|
|
public class AppointmentsController {
|
|
|
|
private final AppointmentBook appointmentBook;
|
|
|
|
@Autowired
|
|
public AppointmentsController(AppointmentBook appointmentBook) {
|
|
this.appointmentBook = appointmentBook;
|
|
}
|
|
|
|
<emphasis role="bold">@RequestMapping(method = RequestMethod.GET)</emphasis>
|
|
public Map<String, Appointment> get() {
|
|
return appointmentBook.getAppointmentsForToday();
|
|
}
|
|
|
|
<emphasis role="bold">@RequestMapping(value="/{day}", method = RequestMethod.GET)</emphasis>
|
|
public Map<String, Appointment> getForDay(@PathVariable @DateTimeFormat(iso=ISO.DATE) Date day, Model model) {
|
|
return appointmentBook.getAppointmentsForDay(day);
|
|
}
|
|
|
|
<emphasis role="bold">@RequestMapping(value="/new", method = RequestMethod.GET)</emphasis>
|
|
public AppointmentForm getNewForm() {
|
|
return new AppointmentForm();
|
|
}
|
|
|
|
<emphasis role="bold">@RequestMapping(method = RequestMethod.POST)</emphasis>
|
|
public String add(@Valid AppointmentForm appointment, BindingResult result) {
|
|
if (result.hasErrors()) {
|
|
return "appointments/new";
|
|
}
|
|
appointmentBook.addAppointment(appointment);
|
|
return "redirect:/appointments";
|
|
}
|
|
}</programlisting>
|
|
|
|
<para>In the example, the <interfacename>@RequestMapping</interfacename>
|
|
is used in a number of places. The first usage is on the type (class)
|
|
level, which indicates that all handling methods on this controller are
|
|
relative to the <filename>/appointments</filename> path. The
|
|
<methodname>get()</methodname> method has a further
|
|
<interfacename>@RequestMapping</interfacename> refinement: it only
|
|
accepts GET requests, meaning that an HTTP GET for
|
|
<filename>/appointments</filename> invokes this method. The
|
|
<methodname>post()</methodname> has a similar refinement, and the
|
|
<methodname>getNewForm()</methodname> combines the definition of HTTP
|
|
method and path into one, so that GET requests for
|
|
<filename>appointments/new</filename> are handled by that method.</para>
|
|
|
|
<para>The <methodname>getForDay()</methodname> method shows another
|
|
usage of <interfacename>@RequestMapping</interfacename>: URI templates.
|
|
(See <link linkend="mvc-ann-requestmapping-uri-templates">the next
|
|
section </link>).</para>
|
|
|
|
<para>A <interfacename>@RequestMapping</interfacename> on the class
|
|
level is not required. Without it, all paths are simply absolute, and
|
|
not relative. The following example from the PetClinic sample
|
|
application shows a multi-action controller using
|
|
<classname>@RequestMapping</classname>:</para>
|
|
|
|
<programlisting language="java">@Controller
|
|
public class ClinicController {
|
|
|
|
private final Clinic clinic;
|
|
|
|
@Autowired
|
|
public ClinicController(Clinic clinic) {
|
|
this.clinic = clinic;
|
|
}
|
|
|
|
<emphasis role="bold">@RequestMapping("/")</emphasis>
|
|
public void welcomeHandler() {
|
|
}
|
|
|
|
<emphasis role="bold">@RequestMapping("/vets")</emphasis>
|
|
public ModelMap vetsHandler() {
|
|
return new ModelMap(this.clinic.getVets());
|
|
}
|
|
|
|
}</programlisting>
|
|
|
|
<tip>
|
|
<title>Working with interface-based @Controller classes</title>
|
|
<para>A common pitfall when working with annotated controller classes
|
|
happens when applying functionality that requires creating a proxy
|
|
proxy for the controller object (e.g.
|
|
<interfacename>@Transactional</interfacename> methods). Usually you
|
|
will introduce an interface for the controller in order to use JDK
|
|
dynamic proxies. To make this work you must move the
|
|
<interfacename>@RequestMapping</interfacename> annotations to the
|
|
interface as as the mapping mechanism can only "see" the interface
|
|
exposed by the proxy. As an alternative, you may choose to activate
|
|
<code>proxy-target-class="true"</code> in the configuration for the
|
|
functionality applied to the controller (in our transaction scenario
|
|
in <code><tx:annotation-driven /></code>). Doing so indicates
|
|
that CGLIB-based subclass proxies should be used instead of
|
|
interface-based JDK proxies. For more information on various proxying
|
|
mechanisms see <xref linkend="aop-proxying"/>.</para>
|
|
</tip>
|
|
|
|
<section id="mvc-ann-requestmapping-uri-templates">
|
|
<title>URI Templates</title>
|
|
|
|
<para>To access parts of a request URL in your handling methods, use
|
|
the <emphasis><emphasis>URI templates</emphasis></emphasis> in the
|
|
<interfacename>@RequestMapping</interfacename> path value.</para>
|
|
|
|
<sidebar id="mvc-uri-templates">
|
|
<title>URI Templates</title>
|
|
|
|
<para>A URI Template is a URI-like string, containing one or more
|
|
variable names. When you substitute values for these variables, the
|
|
template becomes a URI. The <ulink
|
|
url="http://bitworking.org/projects/URI-Templates/">proposed
|
|
RFC</ulink> for URI Templates defines how a URI is parameterized.
|
|
For example, the URI Template</para>
|
|
|
|
<programlisting>http://www.example.com/users/{userid}</programlisting>
|
|
|
|
<para>contains the variable <emphasis>userid</emphasis>. If we
|
|
assign the variable the value fred, the URI Template yields:</para>
|
|
|
|
<programlisting>http://www.example.com/users/fred</programlisting>
|
|
|
|
<para>During the processing of a request, the URI can be compared to
|
|
an expected URI Template in order to extract a collection of
|
|
variables.</para>
|
|
</sidebar>
|
|
|
|
<para>Use the <interfacename>@PathVariable</interfacename> method
|
|
parameter annotation to indicate that a method parameter should be
|
|
bound to the value of a URI template variable.</para>
|
|
|
|
<para>The following code snippet shows the usage of a single
|
|
<interfacename>@PathVariable</interfacename> in a controller
|
|
method:</para>
|
|
|
|
<programlisting language="java">@RequestMapping(value="/owners/{ownerId}", method=RequestMethod.GET)
|
|
public String findOwner(<emphasis role="bold">@PathVariable</emphasis> String ownerId, Model model) {
|
|
Owner owner = ownerService.findOwner(ownerId);
|
|
model.addAttribute("owner", owner);
|
|
return "displayOwner";
|
|
}
|
|
</programlisting>
|
|
|
|
<para>The URI Template "<literal>/owners/{ownerId}</literal>"
|
|
specifies the variable name <emphasis>ownerId</emphasis>. When the
|
|
controller handles this request, the value of
|
|
<emphasis>ownerId</emphasis> is set to the value in the request URI.
|
|
For example, when a request comes in for /owners/fred, the value fred
|
|
is bound to the method parameter <literal>String
|
|
ownerId</literal>.</para>
|
|
|
|
<!-- MLP: Bev Review -->
|
|
<para>The matching of method parameter names to URI Template variable
|
|
names can only be done if your code is compiled with debugging
|
|
enabled. If you do not have debugging enabled, you must specify the
|
|
name of the URI Template variable name in the @PathVariable annotation
|
|
in order to bind the resolved value of the variable name to a method
|
|
parameter. For example:</para>
|
|
|
|
<programlisting language="java">@RequestMapping(value="/owners/{ownerId}", method=RequestMethod.GET)
|
|
public String findOwner(<emphasis role="bold">@PathVariable</emphasis>("ownerId") String ownerId, Model model) {
|
|
// implementation omitted
|
|
}</programlisting>
|
|
|
|
<para>You can also use a controller method with the following
|
|
signature:</para>
|
|
|
|
<programlisting language="java">@RequestMapping(value="/owners/{ownerId}", method=RequestMethod.GET)
|
|
public String findOwner(<emphasis role="bold">@PathVariable</emphasis>("ownerId") String theOwner, Model model) {
|
|
// implementation omitted
|
|
}</programlisting>
|
|
|
|
<para>You can use multiple @PathVariable annotations to bind <!--specify: to bind *what* to multiple URI template variables? method parameter String ownerId?-->to
|
|
multiple URI Template variables:</para>
|
|
|
|
<programlisting language="java">@RequestMapping(value="/owners/{ownerId}/pets/{petId}", method=RequestMethod.GET)
|
|
public String findPet(<emphasis role="bold">@PathVariable</emphasis> String ownerId, <emphasis
|
|
role="bold">@PathVariable</emphasis> String petId, Model model) {
|
|
Owner owner = ownerService.findOwner(ownderId);
|
|
Pet pet = owner.getPet(petId);
|
|
model.addAttribute("pet", pet);
|
|
return "displayPet";
|
|
}
|
|
</programlisting>
|
|
|
|
<para>The following code snippet shows the usage of path variables on
|
|
a relative path, so that the <methodname>findPet()</methodname> method
|
|
will be invoked for <filename>/owners/42/pets/21</filename>, for
|
|
instance.</para>
|
|
|
|
<programlisting language="java">@Controller
|
|
@RequestMapping(<emphasis role="bold">"/owners/{ownerId}"</emphasis>)
|
|
public class RelativePathUriTemplateController {
|
|
|
|
@RequestMapping(<emphasis role="bold">"/pets/{petId}"</emphasis>)
|
|
public void findPet(@PathVariable String ownerId, @PathVariable String petId, Model model) {
|
|
// implementation omitted
|
|
}
|
|
}
|
|
</programlisting>
|
|
|
|
<tip>
|
|
<para>Method parameters that are decorated with the
|
|
<interfacename>@PathVariable</interfacename> annotation can be of
|
|
<emphasis role="bold">any simple type </emphasis>such as int, long,
|
|
Date, etc. Spring automatically converts to the appropriate type and
|
|
throws a <classname>TypeMismatchException</classname> if the type is
|
|
not correct. You can further customize this conversion process by
|
|
customizing the data binder. See <xref
|
|
linkend="mvc-ann-webdatabinder" />.</para>
|
|
</tip>
|
|
</section>
|
|
|
|
<section id="mvc-ann-requestmapping-advanced">
|
|
<title>Advanced <interfacename>@RequestMapping</interfacename>
|
|
options</title>
|
|
|
|
<para>In addition to URI templates, the
|
|
<interfacename>@RequestMapping</interfacename> annotation also
|
|
supports Ant-style path patterns (for example,
|
|
<filename>/myPath/*.do</filename>). A combination of URI templates and
|
|
Ant-style globs is also supported (for example,
|
|
<filename>/owners/*/pets/{petId}</filename>).</para>
|
|
|
|
<para>The handler method names are taken into account for narrowing if
|
|
no path was specified explicitly, according to the specified
|
|
<interfacename>org.springframework.web.servlet.mvc.multiaction.MethodNameResolver</interfacename>
|
|
(by default an
|
|
<classname>org.springframework.web.servlet.mvc.multiaction.InternalPathMethodNameResolver</classname>).
|
|
This only applies if annotation mappings do not specify a path mapping
|
|
explicitly. In other words, the method name is only used for narrowing
|
|
among a set of matching methods; it does not constitute a primary path
|
|
mapping itself.</para>
|
|
|
|
<para>If you have a single default method (without explicit path
|
|
mapping), then all requests without a more specific mapped method
|
|
found are dispatched to it. If you have multiple such default methods,
|
|
then the method name is taken into account for choosing between
|
|
them.</para>
|
|
|
|
<para>You can narrow path mappings through parameter conditions: a
|
|
sequence of "myParam=myValue" style expressions, with a request only
|
|
mapped if each such parameter is found to have the given value. For
|
|
example: <programlisting language="java">@Controller
|
|
@RequestMapping("/owners/{ownerId}")
|
|
public class RelativePathUriTemplateController {
|
|
|
|
@RequestMapping(value = "/pets/{petId}", <emphasis role="bold">params="myParam=myValue"</emphasis>)
|
|
public void findPet(@PathVariable String ownerId, @PathVariable String petId, Model model) {
|
|
// implementation omitted
|
|
}
|
|
}
|
|
</programlisting> "myParam" style expressions are also supported, with such
|
|
parameters having to be present in the request (allowed to have any
|
|
value). <!--I don't understand the preceding sentence. Can you reword?-->Finally,
|
|
"!myParam" style expressions indicate that the specified parameter is
|
|
<emphasis>not</emphasis> supposed to be present in the request.</para>
|
|
|
|
<para>Similarly, path mappings can be narrowed down through header
|
|
conditions:</para>
|
|
|
|
<programlisting language="java">@Controller
|
|
@RequestMapping("/owners/{ownerId}")
|
|
public class RelativePathUriTemplateController {
|
|
|
|
@RequestMapping(value = "/pets", method = RequestMethod.POST, <emphasis
|
|
role="bold">headers="content-type=text/*"</emphasis>)
|
|
public void addPet(Pet pet, @PathVariable String ownerId) {
|
|
// implementation omitted
|
|
}
|
|
}</programlisting>
|
|
|
|
<para>In the above example, the <methodname>addPet()</methodname>
|
|
method is only invoked when the <literal>content-type</literal>
|
|
matches the <literal>text/*</literal> pattern, for example,
|
|
<literal>text/xml</literal>.</para>
|
|
</section>
|
|
|
|
<section id="mvc-ann-requestmapping-arguments">
|
|
<title>Supported handler method arguments and return types</title>
|
|
|
|
<para>Handler methods that are annotated with
|
|
<classname>@RequestMapping</classname> can have very flexible
|
|
signatures. Most of them can be used in arbitrary order (see below for
|
|
more details). <itemizedlist>
|
|
<listitem>
|
|
<para>Request or response objects (Servlet API). Choose any
|
|
specific request or response type, for example
|
|
<interfacename>ServletRequest</interfacename> or
|
|
<interfacename>HttpServletRequest</interfacename>.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>Session object (Servlet API): of type
|
|
<interfacename>HttpSession</interfacename>. An argument of this
|
|
type enforces the presence of a corresponding session. As a
|
|
consequence, such an argument is never
|
|
<literal>null</literal>.</para>
|
|
|
|
<note>
|
|
<para>Session access may not be thread-safe, in particular in
|
|
a Servlet environment. Consider setting the
|
|
<classname>AnnotationMethodHandlerAdapter</classname>'s
|
|
"synchronizeOnSession" flag to "true" if multiple requests are
|
|
allowed to access a session concurrently.</para>
|
|
</note>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para><classname>org.springframework.web.context.request.WebRequest</classname>
|
|
or
|
|
<classname>org.springframework.web.context.request.NativeWebRequest</classname>.
|
|
Allows for generic request parameter access as well as
|
|
request/session attribute access, without ties to the native
|
|
Servlet/Portlet API.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para><classname>java.util.Locale</classname> for the current
|
|
request locale, determined by the most specific locale resolver
|
|
available, in effect, the configured
|
|
<interfacename>LocaleResolver</interfacename> in a Servlet
|
|
environment.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para><classname>java.io.InputStream</classname> /
|
|
<classname>java.io.Reader</classname> for access to the
|
|
request's content. This value is the raw InputStream/Reader as
|
|
exposed by the Servlet API.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para><classname>java.io.OutputStream</classname> /
|
|
<classname>java.io.Writer</classname> for generating the
|
|
response's content. This value is the raw OutputStream/Writer as
|
|
exposed by the Servlet API.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para><interfacename>java.security.Principal</interfacename>
|
|
containing the currently authenticated user.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para><classname>@PathVariable</classname> annotated parameters
|
|
for access to URI template variables. See <xref
|
|
linkend="mvc-ann-requestmapping-uri-templates" />.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para><classname>@RequestParam</classname> annotated parameters
|
|
for access to specific Servlet request parameters. Parameter
|
|
values are converted to the declared method argument type. See
|
|
<xref linkend="mvc-ann-requestparam" />.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para><interfacename>@RequestHeader</interfacename> annotated parameters
|
|
for access to specific Servlet request HTTP headers. Parameter
|
|
values are converted to the declared method argument
|
|
type.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para><interfacename>@RequestBody</interfacename> annotated parameters
|
|
for access to the HTTP request body. Parameter values are
|
|
converted to the declared method argument type using
|
|
<interfacename>HttpMessageConverter</interfacename>s. See <xref
|
|
linkend="mvc-ann-requestbody" />.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para><classname>HttpEntity<?></classname> parameters
|
|
for access to the Servlet request HTTP headers and contents. The request stream will be
|
|
converted to the entity body using
|
|
<interfacename>HttpMessageConverter</interfacename>s. See <xref
|
|
linkend="mvc-ann-httpentity" />.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para><interfacename>java.util.Map</interfacename> /
|
|
<interfacename>org.springframework.ui.Model</interfacename> /
|
|
<classname>org.springframework.ui.ModelMap</classname> for
|
|
enriching the implicit model that is exposed to the web
|
|
view.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>Command or form objects to bind parameters to: as bean
|
|
properties or fields, <!--What do you mean by *as bean properties or fields*, what does that refer to? Why do you have a colon? Don't get this line.--><!--*to bind parameters to* is awkward. Avoid slashes as with *command/form objects*. Do you mean command or form objects? Revise.-->with
|
|
customizable type conversion, depending on
|
|
<classname>@InitBinder</classname> methods and/or the
|
|
HandlerAdapter configuration. See the
|
|
<literal>webBindingInitializer</literal> property on
|
|
<classname>AnnotationMethodHandlerAdapter</classname>. Such
|
|
command objects along with their validation results will be
|
|
exposed as model attributes by default, using the non-qualified
|
|
command class name in property notation. <!--Who or what uses the non-qualified class name in property notation? Is this something you have to set up?-->For
|
|
example, "orderAddress" for type "mypackage.OrderAddress".
|
|
Specify a parameter-level <classname>ModelAttribute</classname>
|
|
annotation for declaring a specific model attribute name.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para><classname>org.springframework.validation.Errors</classname>
|
|
/
|
|
<classname>org.springframework.validation.BindingResult</classname>
|
|
validation results for a preceding command or form object (the
|
|
immediately preceding method argument).</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para><classname>org.springframework.web.bind.support.SessionStatus</classname>
|
|
status handle for marking form processing as complete, which
|
|
triggers the cleanup of session attributes that have been
|
|
indicated by the <classname>@SessionAttributes</classname>
|
|
annotation at the handler type level.</para>
|
|
</listitem>
|
|
</itemizedlist></para>
|
|
|
|
<para>The <interfacename>Errors</interfacename> or
|
|
<interfacename>BindingResult</interfacename> parameters have to follow
|
|
the model object that is being bound immediately as the method
|
|
signature might have more that one model object and Spring will create
|
|
a separate <interfacename>BindingResult</interfacename> instance for
|
|
each of them so the following sample won't work:</para>
|
|
|
|
<example>
|
|
<title>Invalid ordering of BindingResult and @ModelAttribute</title>
|
|
|
|
<programlisting language="java">@RequestMapping(method = RequestMethod.POST)
|
|
public String processSubmit(<emphasis role="bold">@ModelAttribute("pet") Pet pet</emphasis>,
|
|
Model model, <emphasis role="bold">BindingResult result</emphasis>) { … }</programlisting>
|
|
|
|
<para>Note, that there is a <interfacename>Model</interfacename>
|
|
parameter in between <classname>Pet</classname> and
|
|
<interfacename>BindingResult</interfacename>. To get this working
|
|
you have to reorder the parameters as follows:</para>
|
|
|
|
<programlisting language="java">@RequestMapping(method = RequestMethod.POST)
|
|
public String processSubmit(<emphasis role="bold">@ModelAttribute("pet") Pet pet</emphasis>,
|
|
<emphasis role="bold">BindingResult result</emphasis>, Model model) { … }</programlisting>
|
|
</example>
|
|
|
|
<para>The following return types are supported for handler methods:
|
|
<itemizedlist>
|
|
<listitem>
|
|
<para>A <classname>ModelAndView</classname> object, with the
|
|
model implicitly enriched with command objects and the results
|
|
of <literal>@ModelAttribute</literal> annotated reference data
|
|
accessor methods.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>A <interfacename>Model</interfacename> object, with the
|
|
view name implicitly determined through a
|
|
<interfacename>RequestToViewNameTranslator</interfacename> and
|
|
the model implicitly enriched with command objects and the
|
|
results of <literal>@ModelAttribute</literal> annotated
|
|
reference data accessor methods.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>A <interfacename>Map</interfacename> object for exposing a
|
|
model, with the view name implicitly determined through a
|
|
<interfacename>RequestToViewNameTranslator</interfacename> and
|
|
the model implicitly enriched with command objects and the
|
|
results of <literal>@ModelAttribute</literal> annotated
|
|
reference data accessor methods.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>A <interfacename>View</interfacename> object, with the
|
|
model implicitly determined through command objects and
|
|
<literal>@ModelAttribute</literal> annotated reference data
|
|
accessor methods. The handler method may also programmatically
|
|
enrich the model by declaring a
|
|
<interfacename>Model</interfacename> argument (see above).<!--see above where? Need more explicit reference. same problem with next item.--></para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>A <classname>String</classname> value that is interpreted
|
|
as the logical view name, with the model implicitly determined
|
|
through command objects and <literal>@ModelAttribute</literal>
|
|
annotated reference data accessor methods. The handler method
|
|
may also programmatically enrich the model by declaring a
|
|
<interfacename>Model</interfacename> argument (see
|
|
above).</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para><literal>void</literal> if the method handles the response
|
|
itself (by writing the response content directly, declaring an
|
|
argument of type <interfacename>ServletResponse</interfacename>
|
|
/ <interfacename>HttpServletResponse</interfacename> for that
|
|
purpose) or if the view name is supposed to be implicitly
|
|
determined through a
|
|
<interfacename>RequestToViewNameTranslator</interfacename> (not
|
|
declaring a response argument in the handler method
|
|
signature).</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>If the method is annotated with
|
|
<interfacename>@ResponseBody</interfacename>, the return type is
|
|
written to the response HTTP body. The return value will be
|
|
converted to the declared method argument type using
|
|
<interfacename>HttpMessageConverter</interfacename>s. See <xref
|
|
linkend="mvc-ann-responsebody" />.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>A <classname>HttpEntity<?></classname> or
|
|
<classname>ResponseEntity<?></classname> object
|
|
to provide access to the Servlet reponse HTTP headers and
|
|
contents. The entity body will be converted to the response
|
|
stream using
|
|
<interfacename>HttpMessageConverter</interfacename>s. See <xref
|
|
linkend="mvc-ann-httpentity" />.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>Any other return type is considered to be a single model
|
|
attribute to be exposed to the view, using the attribute name
|
|
specified through <literal>@ModelAttribute</literal> at the
|
|
method level (or the default attribute name based on the return
|
|
type class name). The model is implicitly enriched with command
|
|
objects and the results of <literal>@ModelAttribute</literal>
|
|
annotated reference data accessor methods.</para>
|
|
</listitem>
|
|
</itemizedlist></para>
|
|
</section>
|
|
|
|
<section id="mvc-ann-requestparam">
|
|
<title>Binding request parameters to method parameters with
|
|
<interfacename>@RequestParam</interfacename></title>
|
|
|
|
<para>Use the <classname>@RequestParam</classname> annotation to bind
|
|
request parameters to a method parameter in your controller.</para>
|
|
|
|
<para>The following code snippet shows the usage:</para>
|
|
|
|
<programlisting language="java">@Controller
|
|
@RequestMapping("/pets")
|
|
@SessionAttributes("pet")
|
|
public class EditPetForm {
|
|
|
|
<lineannotation>// ...</lineannotation>
|
|
|
|
@RequestMapping(method = RequestMethod.GET)
|
|
public String setupForm(<emphasis role="bold">@RequestParam("petId") int petId</emphasis>, ModelMap model) {
|
|
Pet pet = this.clinic.loadPet(petId);
|
|
model.addAttribute("pet", pet);
|
|
return "petForm";
|
|
}
|
|
|
|
<lineannotation>// ...</lineannotation>
|
|
</programlisting>
|
|
|
|
<para>Parameters using this annotation are required by default, but
|
|
you can specify that a parameter is optional by setting
|
|
<interfacename>@RequestParam</interfacename>'s
|
|
<literal>required</literal> attribute to <literal>false</literal>
|
|
(e.g., <literal>@RequestParam(value="id",
|
|
required=false)</literal>).</para>
|
|
</section>
|
|
|
|
<section id="mvc-ann-requestbody">
|
|
<title>Mapping the request body with the @RequestBody
|
|
annotation</title>
|
|
|
|
<para>The <classname>@RequestBody</classname> method parameter
|
|
annotation indicates that a method parameter should be bound to the
|
|
value of the HTTP request body. For example:</para>
|
|
|
|
<programlisting language="java">@RequestMapping(value = "/something", method = RequestMethod.PUT)
|
|
public void handle(@RequestBody String body, Writer writer) throws IOException {
|
|
writer.write(body);
|
|
}</programlisting>
|
|
|
|
<para>You convert the request body to the method argument by using an
|
|
<interfacename>HttpMessageConverter</interfacename>.
|
|
<interfacename>HttpMessageConverter</interfacename> is responsible for
|
|
converting from the HTTP request message to an object and converting
|
|
from an object to the HTTP response body.
|
|
<classname>DispatcherServlet</classname> supports annotation based
|
|
processing using the
|
|
<classname>DefaultAnnotationHandlerMapping</classname> and
|
|
<classname>AnnotationMethodHandlerAdapter</classname>. In Spring 3.0
|
|
the <classname>AnnotationMethodHandlerAdapter</classname> is extended
|
|
to support the <classname>@RequestBody</classname> and has the
|
|
following <interfacename>HttpMessageConverters</interfacename>
|
|
registered by default if not using the MVC namespace:</para>
|
|
|
|
<itemizedlist>
|
|
<listitem>
|
|
<para><classname>ByteArrayHttpMessageConverter</classname>
|
|
converts byte arrays.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para><classname>StringHttpMessageConverter</classname> converts
|
|
strings.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para><classname>FormHttpMessageConverter</classname> converts
|
|
form data to/from a MultiValueMap<String, String>.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para><classname>SourceHttpMessageConverter</classname> converts
|
|
to/from a javax.xml.transform.Source.</para>
|
|
</listitem>
|
|
</itemizedlist>
|
|
|
|
<para>For more information on these converters, see <link
|
|
linkend="rest-message-conversion">Message Converters</link>.
|
|
Also see <xref linkend="mvc-annotation-driven"/> for information
|
|
on the default message converters set up by the MVC namespace.</para>
|
|
|
|
<para>The <classname>MarshallingHttpMessageConverter</classname>
|
|
requires a <interfacename>Marshaller</interfacename> and
|
|
<interfacename>Unmarshaller</interfacename> from the
|
|
<classname>org.springframework.oxm</classname> package to be
|
|
configured on an instance of
|
|
<classname>AnnotationMethodHandlerAdapter</classname> in the
|
|
application context. For example:</para>
|
|
|
|
<programlisting language="xml"><bean class="org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter">
|
|
<property name="messageConverters">
|
|
<util:list id="beanList">
|
|
<ref bean="stringHttpMessageConverter"/>
|
|
<ref bean="marshallingHttpMessageConverter"/>
|
|
</util:list>
|
|
</property
|
|
</bean>
|
|
|
|
<bean id="stringHttpMessageConverter"
|
|
class="org.springframework.http.converter.StringHttpMessageConverter"/>
|
|
|
|
<bean id="marshallingHttpMessageConverter"
|
|
class="org.springframework.http.converter.xml.MarshallingHttpMessageConverter">
|
|
<property name="marshaller" ref="castorMarshaller" />
|
|
<property name="unmarshaller" ref="castorMarshaller" />
|
|
</bean>
|
|
|
|
<bean id="castorMarshaller" class="org.springframework.oxm.castor.CastorMarshaller"/>
|
|
</programlisting>
|
|
</section>
|
|
|
|
<section id="mvc-ann-responsebody">
|
|
<title>Mapping the response body with the <interfacename>@ResponseBody</interfacename>
|
|
annotation</title>
|
|
|
|
<para>The <interfacename>@ResponseBody</interfacename> annotation is
|
|
similar to <interfacename>@RequestBody</interfacename>. This
|
|
annotation can be put on a method and
|
|
indicates that the return type should be written straight to the HTTP
|
|
response body (and not placed in a Model, or interpreted as a view
|
|
name). For example:</para>
|
|
|
|
<programlisting language="java">@RequestMapping(value = "/something", method = RequestMethod.PUT)
|
|
@ResponseBody
|
|
public String helloWorld() {
|
|
return "Hello World";
|
|
}</programlisting>
|
|
|
|
<para>The above example will result in the text <literal>Hello
|
|
World</literal> being written to the HTTP response stream.</para>
|
|
|
|
<para>As with <interfacename>@RequestBody</interfacename>, Spring
|
|
converts the returned object to a response body by using an
|
|
<interfacename>HttpMessageConverter</interfacename>. For more
|
|
information on these converters, see the previous section and <link
|
|
linkend="rest-message-conversion">Message Converters</link>.</para>
|
|
</section>
|
|
|
|
<section id="mvc-ann-httpentity">
|
|
<title>Using <classname>HttpEntity<?></classname></title>
|
|
|
|
<para>The <classname>HttpEntity</classname> is similar to
|
|
<interfacename>@RequestBody</interfacename> and
|
|
<interfacename>@ResponseBody</interfacename>. Besides getting
|
|
access to the request and response body, <classname>HttpEntity</classname>
|
|
(and the response-specific subclass <classname>ResponseEntity</classname>)
|
|
also allows access to the request and response headers, like so:</para>
|
|
|
|
<programlisting language="java">@RequestMapping("/something")
|
|
public ResponseEntity<String> handle(HttpEntity<byte[]> requestEntity) throws UnsupportedEncodingException {
|
|
String requestHeader = requestEntity.getHeaders().getFirst("MyRequestHeader"));
|
|
byte[] requestBody = requestEntity.getBody();
|
|
// do something with request header and body
|
|
|
|
HttpHeaders responseHeaders = new HttpHeaders();
|
|
responseHeaders.set("MyResponseHeader", "MyValue");
|
|
return new ResponseEntity<String>("Hello World", responseHeaders, HttpStatus.CREATED);
|
|
}</programlisting>
|
|
|
|
<para>The above example gets the value of the "MyRequestHeader" request
|
|
header, and reads the body as a byte array. It adds the "MyResponseHeader"
|
|
to the response, writes <literal>Hello World</literal> to the response
|
|
stream, and sets the response status code to 201 (Created).</para>
|
|
|
|
<para>As with <interfacename>@RequestBody</interfacename> and
|
|
<interfacename>@ResponseBody</interfacename>, Spring
|
|
uses <interfacename>HttpMessageConverter</interfacename> to convert
|
|
from and to the request and response streams. For more
|
|
information on these converters, see the previous section and <link
|
|
linkend="rest-message-conversion">Message Converters</link>.</para>
|
|
</section>
|
|
|
|
<section id="mvc-ann-modelattrib">
|
|
<title>Providing a link to data from the model with
|
|
<classname>@ModelAttribute</classname></title>
|
|
|
|
<para><classname>@ModelAttribute</classname> has two usage scenarios
|
|
in controllers. When you place it on a
|
|
method parameter, <classname>@ModelAttribute</classname> maps a model
|
|
attribute to the specific, annotated method parameter (see the
|
|
<literal>processSubmit()</literal> method below). This is how the
|
|
controller gets a reference to the object holding the data entered in
|
|
the form.</para>
|
|
|
|
<para>You can also use <classname>@ModelAttribute</classname> at the
|
|
method level to provide <emphasis>reference data</emphasis> for the
|
|
model (see the <literal>populatePetTypes()</literal> method in the
|
|
following example). For this usage the method signature can contain
|
|
the same types as documented previously for the
|
|
<classname>@RequestMapping</classname> annotation.</para>
|
|
|
|
<note>
|
|
<para><classname>@ModelAttribute</classname> annotated methods are
|
|
executed <emphasis>before</emphasis> the chosen
|
|
<classname>@RequestMapping</classname> annotated handler method.
|
|
They effectively pre-populate the implicit model with specific
|
|
attributes, often loaded from a database. Such an attribute can then
|
|
already be accessed through <classname>@ModelAttribute</classname>
|
|
annotated handler method parameters in the chosen handler method,
|
|
potentially with binding and validation applied to it.</para>
|
|
</note>
|
|
|
|
<para>The following code snippet shows these two usages of this
|
|
annotation:</para>
|
|
|
|
<programlisting language="java">@Controller
|
|
@RequestMapping("/owners/{ownerId}/pets/{petId}/edit")
|
|
@SessionAttributes("pet")
|
|
public class EditPetForm {
|
|
|
|
<lineannotation>// ...</lineannotation>
|
|
|
|
<emphasis role="bold">@ModelAttribute("types")</emphasis>
|
|
public Collection<PetType> populatePetTypes() {
|
|
return this.clinic.getPetTypes();
|
|
}
|
|
|
|
@RequestMapping(method = RequestMethod.POST)
|
|
public String processSubmit(
|
|
<emphasis role="bold">@ModelAttribute("pet") Pet pet</emphasis>,
|
|
BindingResult result, SessionStatus status) {
|
|
|
|
new PetValidator().validate(pet, result);
|
|
if (result.hasErrors()) {
|
|
return "petForm";
|
|
}
|
|
else {
|
|
this.clinic.storePet(pet);
|
|
status.setComplete();
|
|
return "redirect:owner.do?ownerId=" + pet.getOwner().getId();
|
|
}
|
|
}
|
|
|
|
}</programlisting>
|
|
</section>
|
|
|
|
<section id="mvc-ann-sessionattrib">
|
|
<title>Specifying attributes to store in a session with
|
|
<classname>@SessionAttributes</classname></title>
|
|
|
|
<para>The type-level <classname>@SessionAttributes</classname>
|
|
annotation declares session attributes used by a specific handler.
|
|
This will typically list the names of model attributes or types of
|
|
model attributes which should be transparently stored in the session
|
|
or some conversational storage, serving as form-backing beans between
|
|
subsequent requests.</para>
|
|
|
|
<para>The following code snippet shows the usage of this annotation,
|
|
specifying the model attribute name:</para>
|
|
|
|
<programlisting language="java">@Controller
|
|
@RequestMapping("/editPet.do")
|
|
<emphasis role="bold">@SessionAttributes("pet")</emphasis>
|
|
public class EditPetForm {
|
|
<lineannotation>// ...</lineannotation>
|
|
}</programlisting>
|
|
|
|
<note>
|
|
<para>When using controller interfaces (e.g. for AOP proxying), make sure to
|
|
consistently put <emphasis>all</emphasis> your mapping annotations - such as
|
|
<interfacename>@RequestMapping</interfacename> and
|
|
<interfacename>@SessionAttributes</interfacename> - on the controller
|
|
<emphasis>interface</emphasis> rather than on the implementation class.
|
|
</para>
|
|
</note>
|
|
</section>
|
|
|
|
<section id="mvc-ann-cookievalue">
|
|
<title>Mapping cookie values with the @CookieValue annotation</title>
|
|
|
|
<para>The <interfacename>@CookieValue</interfacename> annotation
|
|
allows a method parameter to be bound to the value of an HTTP
|
|
cookie.</para>
|
|
|
|
<para>Let us consider that the following cookie has been received with
|
|
an http request:</para>
|
|
|
|
<programlisting>JSESSIONID=415A4AC178C59DACE0B2C9CA727CDD84</programlisting>
|
|
|
|
<para>The following code sample demonstrates how to get the value of
|
|
the <literal>JSESSIONID</literal> cookie:</para>
|
|
|
|
<programlisting language="java">@RequestMapping("/displayHeaderInfo.do")
|
|
public void displayHeaderInfo(<emphasis role="bold">@CookieValue("JSESSIONID")</emphasis> String cookie) {
|
|
|
|
//...
|
|
|
|
}</programlisting>
|
|
|
|
<para>This annotation is supported for annotated handler methods in
|
|
Servlet and Portlet environments.</para>
|
|
</section>
|
|
|
|
<section id="mvc-ann-requestheader">
|
|
<title>Mapping request header attributes with the @RequestHeader
|
|
annotation</title>
|
|
|
|
<para>The <interfacename>@RequestHeader</interfacename> annotation
|
|
allows a method parameter to be bound to a request header.</para>
|
|
|
|
<para>Here is a sample request header:</para>
|
|
|
|
<programlisting>
|
|
Host localhost:8080
|
|
Accept text/html,application/xhtml+xml,application/xml;q=0.9
|
|
Accept-Language fr,en-gb;q=0.7,en;q=0.3
|
|
Accept-Encoding gzip,deflate
|
|
Accept-Charset ISO-8859-1,utf-8;q=0.7,*;q=0.7
|
|
Keep-Alive 300
|
|
</programlisting>
|
|
|
|
<para>The following code sample demonstrates how to get the value of
|
|
the <literal>Accept-Encoding</literal> and
|
|
<literal>Keep-Alive</literal> headers:</para>
|
|
|
|
<programlisting language="java">@RequestMapping("/displayHeaderInfo.do")
|
|
public void displayHeaderInfo(<emphasis role="bold">@RequestHeader("Accept-Encoding")</emphasis> String encoding,
|
|
<emphasis role="bold">@RequestHeader("Keep-Alive")</emphasis> long keepAlive) {
|
|
|
|
//...
|
|
|
|
}</programlisting>
|
|
|
|
<para>This annotation is supported for annotated handler methods in
|
|
Servlet and Portlet environments.</para>
|
|
</section>
|
|
|
|
<section id="mvc-ann-webdatabinder">
|
|
<title>Customizing <classname>WebDataBinder</classname>
|
|
initialization</title>
|
|
|
|
<para>To customize request parameter binding with PropertyEditors
|
|
through Spring's <classname>WebDataBinder</classname>, you can use
|
|
either <interfacename>@InitBinder</interfacename>-annotated methods
|
|
within your controller or externalize your configuration by providing
|
|
a custom <interfacename>WebBindingInitializer</interfacename>.</para>
|
|
|
|
<section id="mvc-ann-initbinder">
|
|
<title>Customizing data binding with
|
|
<interfacename>@InitBinder</interfacename></title>
|
|
|
|
<para>Annotating controller methods with
|
|
<interfacename>@InitBinder</interfacename> allows you to configure
|
|
web data binding directly within your controller class.
|
|
<interfacename>@InitBinder</interfacename> identifies methods that
|
|
initialize the <classname>WebDataBinder</classname> that will be
|
|
used to populate command and form object arguments of annotated
|
|
handler methods.</para>
|
|
|
|
<para>Such init-binder methods support all arguments that
|
|
<interfacename>@RequestMapping</interfacename> supports, except for
|
|
command/form objects and corresponding validation result objects.
|
|
Init-binder methods must not have a return value. Thus, they are
|
|
usually declared as <literal>void</literal>. Typical arguments
|
|
include <classname>WebDataBinder</classname> in combination with
|
|
<interfacename>WebRequest</interfacename> or
|
|
<classname>java.util.Locale</classname>, allowing code to register
|
|
context-specific editors.</para>
|
|
|
|
<para>The following example demonstrates the use of
|
|
<interfacename>@InitBinder</interfacename> to configure a
|
|
<classname>CustomDateEditor</classname> for all
|
|
<classname>java.util.Date</classname> form properties.</para>
|
|
|
|
<programlisting language="java">@Controller
|
|
public class MyFormController {
|
|
|
|
<emphasis role="bold">@InitBinder</emphasis>
|
|
public void initBinder(WebDataBinder binder) {
|
|
SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd");
|
|
dateFormat.setLenient(false);
|
|
binder.registerCustomEditor(Date.class, new CustomDateEditor(dateFormat, false));
|
|
}
|
|
|
|
<lineannotation>// ...</lineannotation>
|
|
}</programlisting>
|
|
</section>
|
|
|
|
<section id="mvc-ann-webbindinginitializer">
|
|
<title>Configuring a custom
|
|
<interfacename>WebBindingInitializer</interfacename></title>
|
|
|
|
<para>To externalize data binding initialization, you can provide a
|
|
custom implementation of the
|
|
<interfacename>WebBindingInitializer</interfacename> interface,
|
|
which you then enable by supplying a custom bean configuration for
|
|
an <classname>AnnotationMethodHandlerAdapter</classname>, thus
|
|
overriding the default configuration.</para>
|
|
|
|
<para>The following example from the PetClinic application shows a
|
|
configuration using a custom implementation of the
|
|
<interfacename>WebBindingInitializer</interfacename> interface,
|
|
<classname>org.springframework.samples.petclinic.web.ClinicBindingInitializer</classname>,
|
|
which configures PropertyEditors required by several of the
|
|
PetClinic controllers.</para>
|
|
|
|
<programlisting language="xml"><bean class="org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter">
|
|
<property name="cacheSeconds" value="0" />
|
|
<property name="webBindingInitializer">
|
|
<bean class="org.springframework.samples.petclinic.web.ClinicBindingInitializer" />
|
|
</property>
|
|
</bean>
|
|
</programlisting>
|
|
</section>
|
|
</section>
|
|
</section>
|
|
</section>
|
|
|
|
<section id="mvc-handlermapping">
|
|
<title>Handler mappings</title>
|
|
|
|
<para>In previous versions of Spring, users were required to define
|
|
<interfacename>HandlerMapping</interfacename>s in the web application
|
|
context to map incoming web requests to appropriate handlers. With the
|
|
introduction of Spring 2.5, <!--IMPORTANT: Shouldn't that say Spring 3.0, since that's upcoming release? If you do mean 2.5, then first sentence should say in pre--><!--2.5 versions of Spring, not *previous*. Also in first sentence, I changed Spring MVC to Spring because it refers to a version.-->the
|
|
<classname>DispatcherServlet</classname> enables the
|
|
<classname>DefaultAnnotationHandlerMapping</classname>, which looks for
|
|
<interfacename>@RequestMapping</interfacename> annotations on
|
|
<interfacename>@Controllers</interfacename>. Typically, you do not need to
|
|
override this default mapping, unless you need to override the default
|
|
property values. These properties are:</para>
|
|
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term><literal>interceptors</literal></term>
|
|
<listitem>
|
|
<para>List of interceptors to use.
|
|
<interfacename>HandlerInterceptor</interfacename>s are discussed in
|
|
<xref linkend="mvc-handlermapping-interceptor" />.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><literal>defaultHandler</literal></term>
|
|
<listitem>
|
|
<para>Default handler to use, when this handler mapping does not
|
|
result in a matching handler.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><literal>order</literal></term>
|
|
<listitem>
|
|
<para>Based on the value of the order property (see the
|
|
<literal>org.springframework.core.Ordered</literal> interface),
|
|
Spring sorts all handler mappings available in the context and
|
|
applies the first matching handler.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><literal>alwaysUseFullPath</literal></term>
|
|
<listitem>
|
|
<para>If <literal>true</literal> , Spring uses the full path within
|
|
the current servlet context to find an appropriate handler. If
|
|
<literal>false</literal> (the default), the path within the current
|
|
servlet mapping is used. For example, if a servlet is mapped using
|
|
<literal>/testing/*</literal> and the
|
|
<literal>alwaysUseFullPath</literal> property is set to true,
|
|
<literal>/testing/viewPage.html</literal> is used, whereas if the
|
|
property is set to false, <literal>/viewPage.html</literal> is
|
|
used.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><literal>urlDecode</literal></term>
|
|
<listitem>
|
|
<para>Defaults to <literal>true</literal>, as of Spring 2.5. <!--OK, or do you mean 3.0?-->
|
|
If you prefer to compare encoded paths, set this flag to
|
|
<literal>false</literal>. However, the
|
|
<interfacename>HttpServletRequest</interfacename> always exposes the
|
|
servlet path in decoded form. Be aware that the servlet path will
|
|
not match when compared with encoded paths.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><literal>lazyInitHandlers</literal></term>
|
|
<listitem>
|
|
<para>Allows lazy initialization of <emphasis>singleton</emphasis>
|
|
handlers (prototype handlers are always lazy-initialized). The
|
|
default value is <literal>false</literal>.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
|
|
<note>
|
|
<para>The <literal>alwaysUseFullPath</literal>,
|
|
<literal>urlDecode</literal>, and <literal>lazyInitHandlers</literal>
|
|
properties are only available to subclasses of
|
|
<interfacename>org.springframework.web.servlet.handler.AbstractUrlHandlerMapping</interfacename>.</para>
|
|
</note>
|
|
|
|
<para>The following example shows how to override the default mapping and
|
|
add an interceptor:</para>
|
|
|
|
<programlisting language="xml"><beans>
|
|
<bean id="handlerMapping" class="org.springframework.web.servlet.mvc.annotation.DefaultAnnotationHandlerMapping">
|
|
<property name="interceptors">
|
|
<bean class="example.MyInterceptor"/>
|
|
</property>
|
|
</bean>
|
|
|
|
<beans></programlisting>
|
|
|
|
<section id="mvc-handlermapping-interceptor">
|
|
<title>Intercepting requests - the
|
|
<interfacename>HandlerInterceptor</interfacename> interface<!--Revise head to delete dash. How should it read? Intercepting requests *through* the HandlerInterceptor Interface? *with*?--></title>
|
|
|
|
<para>Spring's handler mapping mechanism includes handler interceptors,
|
|
which are useful when you want to apply specific functionality to
|
|
certain requests, for example, checking for a principal.</para>
|
|
|
|
<para>Interceptors located in the handler mapping must implement
|
|
<interfacename>HandlerInterceptor</interfacename> from the
|
|
<literal>org.springframework.web.servlet</literal> package. This
|
|
interface defines three methods: one is called
|
|
<emphasis>before</emphasis> the actual handler is executed; one is
|
|
called <emphasis>after</emphasis> the handler is executed; and one is
|
|
called <emphasis>after the complete request has finished</emphasis>.
|
|
<!--I suggest identifying each method in parentheses after the reference to it, in sentence above. -->These
|
|
three methods should provide enough flexibility to do all kinds of
|
|
preprocessing and postprocessing.</para>
|
|
|
|
<para>The <literal>preHandle(..)</literal> method returns a boolean
|
|
value. You can use this method to break or continue the processing of
|
|
the execution chain. When this method returns <literal>true</literal>,
|
|
the handler execution chain will continue; when it returns false, the
|
|
<classname>DispatcherServlet</classname> assumes the interceptor itself
|
|
has taken care of requests (and, for example, rendered an appropriate
|
|
view) and does not continue executing the other interceptors and the
|
|
actual handler in the execution chain.</para>
|
|
|
|
<para>The following example defines a handler mapping which maps all
|
|
requests matching the URL patterns "/*.form" and "/*.view" to a
|
|
particular controller, <literal>editAccountFormController</literal>. An
|
|
interceptor has been added that intercepts these requests and reroutes
|
|
the user to a specific page if the time is not between 9 a.m. and 6
|
|
p.m.</para>
|
|
|
|
<programlisting language="xml"><beans>
|
|
<bean id="handlerMapping"
|
|
class="org.springframework.web.servlet.handler.SimpleUrlHandlerMapping">
|
|
<property name="interceptors">
|
|
<list>
|
|
<ref bean="officeHoursInterceptor"/>
|
|
</list>
|
|
</property>
|
|
<property name="mappings">
|
|
<value>
|
|
/*.form=editAccountFormController
|
|
/*.view=editAccountFormController
|
|
</value>
|
|
</property>
|
|
</bean>
|
|
|
|
<bean id="officeHoursInterceptor"
|
|
class="samples.TimeBasedAccessInterceptor">
|
|
<property name="openingTime" value="9"/>
|
|
<property name="closingTime" value="18"/>
|
|
</bean>
|
|
<beans></programlisting>
|
|
|
|
<programlisting language="java">package samples;
|
|
|
|
public class TimeBasedAccessInterceptor extends HandlerInterceptorAdapter {
|
|
|
|
private int openingTime;
|
|
private int closingTime;
|
|
|
|
public void setOpeningTime(int openingTime) {
|
|
this.openingTime = openingTime;
|
|
}
|
|
|
|
public void setClosingTime(int closingTime) {
|
|
this.closingTime = closingTime;
|
|
}
|
|
|
|
public boolean preHandle(
|
|
HttpServletRequest request,
|
|
HttpServletResponse response,
|
|
Object handler) throws Exception {
|
|
|
|
Calendar cal = Calendar.getInstance();
|
|
int hour = cal.get(HOUR_OF_DAY);
|
|
if (openingTime <= hour < closingTime) {
|
|
return true;
|
|
} else {
|
|
response.sendRedirect("http://host.com/outsideOfficeHours.html");
|
|
return false;
|
|
}
|
|
}
|
|
}</programlisting>
|
|
|
|
<para>Any request handled by this mapping is intercepted by the
|
|
<classname>TimeBasedAccessInterceptor</classname>. If the current time
|
|
is outside office hours, the user is redirected to a static HTML file
|
|
that says, for example, you can only access the website during office
|
|
hours.</para>
|
|
|
|
<para>As you can see, the Spring adapter class
|
|
<classname>HandlerInterceptorAdapter</classname> makes it easier to
|
|
extend the <interfacename>HandlerInterceptor</interfacename>
|
|
interface.</para>
|
|
</section>
|
|
</section>
|
|
|
|
<section id="mvc-viewresolver">
|
|
<title>Resolving views</title>
|
|
|
|
<para>All MVC frameworks for web applications provide a way to address
|
|
views. Spring provides view resolvers, which enable you to render models
|
|
in a browser without tying you to a specific view technology. Out of the
|
|
box, Spring enables you to use JSPs, Velocity templates and XSLT views,
|
|
for example. See <xref linkend="view" /> for a discussion of how to
|
|
integrate and use a number of disparate view technologies.</para>
|
|
|
|
<para>The two interfaces that are important to the way Spring handles
|
|
views are <interfacename>ViewResolver</interfacename> and
|
|
<interfacename>View</interfacename>. The
|
|
<interfacename>ViewResolver</interfacename> provides a mapping between
|
|
view names and actual views. The <interfacename>View</interfacename>
|
|
interface addresses the preparation of the request and hands the request
|
|
over to one of the view technologies.</para>
|
|
|
|
<section id="mvc-viewresolver-resolver">
|
|
<title>Resolving views with the
|
|
<interfacename>ViewResolver</interfacename> interface</title>
|
|
|
|
<para>As discussed in <xref linkend="mvc-controller" />, all handler
|
|
methods in the Spring Web MVC controllers must resolve to a logical view
|
|
name, either explicitly (e.g., by returning a <literal>String</literal>,
|
|
<literal>View</literal>, or <literal>ModelAndView</literal>) or
|
|
implicitly (i.e., based on conventions). Views in Spring are addressed
|
|
by a logical view name and are resolved by a view resolver. Spring comes
|
|
with quite a few view resolvers. This table lists most of them; a couple
|
|
of examples follow.</para>
|
|
|
|
<table id="mvc-view-resolvers-tbl">
|
|
<title>View resolvers</title>
|
|
|
|
<tgroup cols="2">
|
|
<colspec colname="c1" colwidth="1*" />
|
|
|
|
<colspec colname="c2" colwidth="2*" />
|
|
|
|
<thead>
|
|
<row>
|
|
<entry><interfacename>ViewResolver</interfacename></entry>
|
|
|
|
<entry>Description</entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry><classname>AbstractCachingViewResolver</classname></entry>
|
|
|
|
<entry>Abstract view resolver that caches views. Often views
|
|
need preparation before they can be used; extending this view
|
|
resolver provides caching.</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><classname>XmlViewResolver</classname></entry>
|
|
|
|
<entry>Implementation of
|
|
<interfacename>ViewResolver</interfacename> that accepts a
|
|
configuration file written in XML with the same DTD as Spring's
|
|
XML bean factories. The default configuration file is
|
|
<literal>/WEB-INF/views.xml</literal>.</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><classname>ResourceBundleViewResolver</classname></entry>
|
|
|
|
<entry>Implementation of
|
|
<interfacename>ViewResolver</interfacename> that uses bean
|
|
definitions in a <classname>ResourceBundle</classname>,
|
|
specified by the bundle base name. Typically you define the
|
|
bundle in a properties file, located in the classpath. <!--Correct to say you define? Seems so, because default implies you can change it.-->The
|
|
default file name is
|
|
<literal>views.properties</literal>.</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><classname>UrlBasedViewResolver</classname></entry>
|
|
|
|
<entry>Simple implementation of the
|
|
<interfacename>ViewResolver</interfacename> interface that
|
|
effects the direct resolution of logical view names to URLs,
|
|
without an explicit mapping definition. This is appropriate if
|
|
your logical names match the names of your view resources in a
|
|
straightforward manner, without the need for arbitrary
|
|
mappings.</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><classname>InternalResourceViewResolver</classname></entry>
|
|
|
|
<entry>Convenient subclass of
|
|
<classname>UrlBasedViewResolver</classname> that supports
|
|
<classname>InternalResourceView</classname> (in effect, Servlets
|
|
and JSPs) and subclasses such as <classname>JstlView</classname>
|
|
and <classname>TilesView</classname>. You can specify the view
|
|
class for all views generated by this resolver by using
|
|
<literal>setViewClass(..)</literal>. See the Javadocs for the
|
|
<classname>UrlBasedViewResolver</classname> class for
|
|
details.</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><classname>VelocityViewResolver</classname> /
|
|
<classname>FreeMarkerViewResolver</classname></entry>
|
|
|
|
<entry>Convenient subclass of
|
|
<classname>UrlBasedViewResolver</classname> that supports
|
|
<classname>VelocityView</classname> (in effect, Velocity
|
|
templates) or <classname>FreeMarkerView</classname>
|
|
,respectively, and custom subclasses of them.</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><classname>ContentNegotiatingViewResolver</classname></entry>
|
|
|
|
<entry>Implementation of the
|
|
<interfacename>ViewResolver</interfacename> interface that
|
|
resolves a view based on the request file name or
|
|
<literal>Accept</literal> header. See <xref
|
|
linkend="mvc-multiple-representations" />.</entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>As an example, with JSP as a view technology, you can use the
|
|
<classname>UrlBasedViewResolver</classname>. This view resolver
|
|
translates a view name to a URL and hands the request over to the
|
|
RequestDispatcher to render the view.</para>
|
|
|
|
<programlisting language="xml"><bean id="viewResolver"
|
|
class="org.springframework.web.servlet.view.UrlBasedViewResolver">
|
|
<property name="viewClass" value="org.springframework.web.servlet.view.JstlView"/>
|
|
<property name="prefix" value="/WEB-INF/jsp/"/>
|
|
<property name="suffix" value=".jsp"/>
|
|
</bean></programlisting>
|
|
|
|
<para>When returning <literal>test</literal> as a logical view name,
|
|
this view resolver forwards the request to the
|
|
<classname>RequestDispatcher</classname> that will send the request to
|
|
<literal>/WEB-INF/jsp/test.jsp</literal>.</para>
|
|
|
|
<para>When you combine different view technologies in a web application,
|
|
you can use the
|
|
<classname>ResourceBundleViewResolver</classname>:</para>
|
|
|
|
<programlisting language="xml"><bean id="viewResolver"
|
|
class="org.springframework.web.servlet.view.ResourceBundleViewResolver">
|
|
<property name="basename" value="views"/>
|
|
<property name="defaultParentView" value="parentView"/>
|
|
</bean></programlisting>
|
|
|
|
<para>The <classname>ResourceBundleViewResolver</classname> inspects the
|
|
<classname>ResourceBundle</classname> identified by the basename, and
|
|
for each view it is supposed to resolve, it uses the value of the
|
|
property <literal>[viewname].(class)</literal> as the view class and the
|
|
value of the property <literal>[viewname].url</literal> as the view url.
|
|
Examples can be found in the next chapter which covers view
|
|
technologies. As you can see, you can identify a parent view, from which
|
|
all views in the properties file <quote>extend</quote>. This way you can
|
|
specify a default view class, for example.</para>
|
|
|
|
<note>
|
|
<para>Subclasses of <classname>AbstractCachingViewResolver</classname>
|
|
cache view instances that they resolve. Caching improves performance
|
|
of certain view technologies. It's possible to turn off the cache by
|
|
setting the <literal>cache</literal> property to
|
|
<literal>false</literal>. Furthermore, if you must refresh a certain
|
|
view at runtime (for example when a Velocity template is modified),
|
|
you can use the <literal>removeFromCache(String viewName, Locale
|
|
loc)</literal> method.</para>
|
|
</note>
|
|
</section>
|
|
|
|
<section id="mvc-viewresolver-chaining">
|
|
<title>Chaining ViewResolvers</title>
|
|
|
|
<para>Spring supports multiple view resolvers. Thus you can chain
|
|
resolvers and, for example, override specific views in certain
|
|
circumstances. You chain view resolvers by adding more than one resolver
|
|
to your application context and, if necessary, by setting the
|
|
<literal>order</literal> property to specify ordering. Remember, the
|
|
higher the order property, the later the view resolver is positioned in
|
|
the chain.</para>
|
|
|
|
<para>In the following example, the chain of view resolvers consists of
|
|
two resolvers, an <classname>InternalResourceViewResolver</classname>,
|
|
which is always automatically positioned as the last resolver in the
|
|
chain, and an <classname>XmlViewResolver</classname> for specifying
|
|
Excel views. Excel views are not supported by the
|
|
<classname>InternalResourceViewResolver</classname>.<!--Do you need to say anything else about excel not being supported by one of resolvers? What if anything is the result?--></para>
|
|
|
|
<programlisting language="xml"><bean id="jspViewResolver" class="org.springframework.web.servlet.view.InternalResourceViewResolver">
|
|
<property name="viewClass" value="org.springframework.web.servlet.view.JstlView"/>
|
|
<property name="prefix" value="/WEB-INF/jsp/"/>
|
|
<property name="suffix" value=".jsp"/>
|
|
</bean>
|
|
|
|
<bean id="excelViewResolver" class="org.springframework.web.servlet.view.XmlViewResolver">
|
|
<property name="order" value="1"/>
|
|
<property name="location" value="/WEB-INF/views.xml"/>
|
|
</bean>
|
|
|
|
<lineannotation><!-- in <literal>views.xml</literal> --></lineannotation>
|
|
|
|
<beans>
|
|
<bean name="report" class="org.springframework.example.ReportExcelView"/>
|
|
</beans></programlisting>
|
|
|
|
<para>If a specific view resolver does not result in a view, Spring
|
|
examines the context for other view resolvers. If additional view
|
|
resolvers exist, Spring continues to inspect them until a view is
|
|
resolved. If no view resolver returns a view, Spring throws a
|
|
<classname>ServletException</classname>.</para>
|
|
|
|
<para>The contract of a view resolver specifies that a view resolver
|
|
<emphasis>can</emphasis> return null to indicate the view could not be
|
|
found. Not all view resolvers do this, however, because in some cases,
|
|
the resolver simply cannot detect whether or not the view exists. For
|
|
example, the <classname>InternalResourceViewResolver</classname> uses
|
|
the <classname>RequestDispatcher</classname> internally, and dispatching
|
|
is the only way to figure out if a JSP exists, but this action can only
|
|
execute once. The same holds for the
|
|
<classname>VelocityViewResolver</classname> and some others. Check the
|
|
Javadoc for the view resolver to see whether it reports non-existing
|
|
views. Thus, putting an
|
|
<classname>InternalResourceViewResolver</classname> in the chain in a
|
|
place other than the last, results in the chain not being fully
|
|
inspected, because the
|
|
<classname>InternalResourceViewResolver</classname> will
|
|
<emphasis>always</emphasis> return a view!<!--I don't understand the logic of this. How can it return a view if no view exists or no view can be found? this paragraph is confusing.--><!--Why would you put InternalResourceViewResolver in place other than last? It's automatically last. --></para>
|
|
</section>
|
|
|
|
<section id="mvc-redirecting">
|
|
<title>Redirecting to views<!--Revise to say what you are redirecting to views. OR are you redirecting views? In that case heading should be Redirecting views.--></title>
|
|
|
|
<para>As mentioned previously, a controller typically returns a logical
|
|
view name, which a view resolver resolves to a particular view
|
|
technology. For view technologies such as JSPs that are processed
|
|
through the Servlet or JSP engine, this resolution is usually handled
|
|
through the combination of
|
|
<classname>InternalResourceViewResolver</classname> and
|
|
<classname>InternalResourceView</classname>, which issues an internal
|
|
forward or include via the Servlet API's
|
|
<literal>RequestDispatcher.forward(..)</literal> method or
|
|
<literal>RequestDispatcher.include()</literal> method. For other view
|
|
technologies, such as Velocity, XSLT, and so on, the view itself writes
|
|
the content directly to the response stream.</para>
|
|
|
|
<para>It is sometimes desirable to issue an HTTP redirect back to the
|
|
client, before the view is rendered. This is desirable, for example,
|
|
when one controller has been called with <literal>POST</literal>ed data,
|
|
and the response is actually a delegation to another controller (for
|
|
example on a successful form submission). In this case, a normal
|
|
internal forward will mean that the other controller will also see the
|
|
same <literal>POST</literal> data, which is potentially problematic if
|
|
it can confuse it with other expected data. Another reason to perform a
|
|
redirect before displaying the result is to eliminate the possibility of
|
|
the user submitting the form data multiple times. In this scenario, the
|
|
browser will first send an initial <literal>POST</literal>; it will then
|
|
receive a response to redirect to a different URL; and finally the
|
|
browser will perform a subsequent <literal>GET</literal> for the URL
|
|
named in the redirect response. Thus, from the perspective of the
|
|
browser, the current page does not reflect the result of a
|
|
<literal>POST</literal> but rather of a <literal>GET</literal>. The end
|
|
effect is that there is no way the user can accidentally
|
|
re-<literal>POST</literal> the same data by performing a refresh. The
|
|
refresh forces a <literal>GET</literal> of the result page, not a resend
|
|
of the initial <literal>POST</literal> data.</para>
|
|
|
|
<section id="mvc-redirecting-redirect-view">
|
|
<title><classname>RedirectView</classname></title>
|
|
|
|
<para>One way to force a redirect as the result of a controller
|
|
response is for the controller to create and return an instance of
|
|
Spring's <classname>RedirectView</classname>. In this case,
|
|
<classname>DispatcherServlet</classname> does not use the normal view
|
|
resolution mechanism. Rather because it has been given the (redirect)
|
|
view already, the <classname>DispatcherServlet</classname> simply
|
|
instructs the view to do its work.</para>
|
|
|
|
<para>The <classname>RedirectView</classname> issues an
|
|
<literal>HttpServletResponse.sendRedirect()</literal> call that
|
|
returns to the client browser as an HTTP redirect. <!--Does preceding happen after what happens in first paragraph? Clarify sequence of events.-->All
|
|
model attributes are exposed as HTTP query parameters. This means that
|
|
the model must contain only objects (generally Strings or objects
|
|
converted to a String representation), which can be readily converted
|
|
to a textual HTTP query parameter.</para>
|
|
|
|
<para>If you use <classname>RedirectView</classname> and the view is
|
|
created by the controller itself, it is recommended that you configure
|
|
the redirect URL to be injected into the controller so that it is not
|
|
baked into the controller but configured in the context along with the
|
|
view names. <!--I revised sentence because it sounds like something you need to do. Also reworded next heading to say what it's about. If not correct,--><!--reword.-->The
|
|
next section discusses this process.</para>
|
|
</section>
|
|
|
|
<section id="mvc-redirecting-redirect-prefix">
|
|
<title>The <literal>redirect:</literal> prefix</title>
|
|
|
|
<para>While the use of <classname>RedirectView</classname> works fine,
|
|
if the controller itself creates the
|
|
<classname>RedirectView</classname>, there is no avoiding the fact
|
|
that the controller is aware that a redirection is happening. This is
|
|
really suboptimal and couples things too tightly. The controller
|
|
should not really care about how the response gets handled. In general
|
|
it should operate only in terms of view names that have been injected
|
|
into it.</para>
|
|
|
|
<para>The special <literal>redirect:</literal> prefix allows you to
|
|
accomplish this. If a view name is returned that has the prefix
|
|
<literal>redirect:</literal>, the
|
|
<classname>UrlBasedViewResolver</classname> (and all subclasses) will
|
|
recognize this as a special indication that a redirect is needed. The
|
|
rest of the view name will be treated as the redirect URL.</para>
|
|
|
|
<para>The net effect is the same as if the controller had returned a
|
|
<classname>RedirectView</classname>, but now the controller itself can
|
|
simply operate in terms of logical view names. A logical view name
|
|
such as <literal>redirect:/my/response/controller.html</literal> will
|
|
redirect relative to the current servlet context, while a name such as
|
|
<literal>redirect:http://myhost.com/some/arbitrary/path.html</literal>
|
|
will redirect to an absolute URL. The important thing is that, as long
|
|
as this redirect view name is injected into the controller like any
|
|
other logical view name, the controller is not even aware that
|
|
redirection is happening.</para>
|
|
</section>
|
|
|
|
<section id="mvc-redirecting-forward-prefix">
|
|
<title>The <literal>forward:</literal> prefix<!--Can you revise this heading to say what you're using the forward prefix to accomplish?--></title>
|
|
|
|
<para>It is also possible to use a special <literal>forward:</literal>
|
|
prefix for view names that are ultimately resolved by
|
|
<classname>UrlBasedViewResolver</classname> and subclasses. This
|
|
creates an <classname>InternalResourceView</classname> (which
|
|
ultimately does a <literal>RequestDispatcher.forward()</literal>)
|
|
around the rest of the view name, which is considered a URL.
|
|
Therefore, this prefix is not useful with
|
|
<classname>InternalResourceViewResolver</classname> and
|
|
<classname>InternalResourceView</classname> (for JSPs for example).
|
|
But the prefix can be helpful when you are primarily using another
|
|
view technology, but still want to force a forward of a resource to be
|
|
handled by the Servlet/JSP engine. (Note that you may also chain
|
|
multiple view resolvers, instead.)<!--I think the preceding sentences were a bit garbled. I tried to reword a bit. And is this paragraph logical?--></para>
|
|
|
|
<para>As with the <literal>redirect:</literal> prefix, if the view
|
|
name with the <literal>forward:</literal> prefix is injected into the
|
|
controller, the controller does not detect that anything special is
|
|
happening in terms of handling the response.<!--Can you reword to clarify the point? The controller does not detect what?--></para>
|
|
</section>
|
|
</section>
|
|
|
|
<section id="mvc-multiple-representations">
|
|
<title><classname>ContentNegotiatingViewResolver</classname></title>
|
|
|
|
<para>The <classname>ContentNegotiatingViewResolver</classname> does not
|
|
resolve views itself but rather delegates to other view resolvers,
|
|
selecting the view that resembles the representation requested by the
|
|
client. Two strategies exist for a client to request a representation
|
|
from the server:</para>
|
|
|
|
<itemizedlist>
|
|
<listitem>
|
|
<para>Use a distinct URI for each resource, typically by using a
|
|
different file extension in the URI. For example, the URI<literal>
|
|
http://www.example.com/users/fred.pdf</literal> requests a PDF
|
|
representation of the user fred, and
|
|
<literal>http://www.example.com/users/fred.xml</literal> requests an
|
|
XML representation.</para>
|
|
</listitem>
|
|
</itemizedlist>
|
|
|
|
<itemizedlist>
|
|
<listitem>
|
|
<para>Use the same URI for the client to locate the resource, but
|
|
set the <literal>Accept</literal> HTTP request header to list the
|
|
<ulink url="http://en.wikipedia.org/wiki/Internet_media_type">media
|
|
types</ulink> that it understands. For example, an HTTP request for
|
|
<literal>http://www.example.com/users/fred</literal> with an
|
|
<literal>Accept</literal> header set to <literal>application/pdf
|
|
</literal>requests a PDF representation of the user fred, while
|
|
<literal>http://www.example.com/users/fred</literal> with an
|
|
<literal>Accept</literal> header set to <literal>text/xml</literal>
|
|
requests an XML representation. This strategy is known as <ulink
|
|
url="http://en.wikipedia.org/wiki/Content_negotiation">content
|
|
negotiation</ulink>.</para>
|
|
</listitem>
|
|
</itemizedlist>
|
|
|
|
<note>
|
|
<para>One issue with the <literal>Accept</literal> header is that it
|
|
is impossible to set it in a web browser within HTML. For example, in
|
|
Firefox, it is fixed to:<!--So how would you set the Accept header as in second bullet, if you can't do it in html? Indicate?--></para>
|
|
|
|
<programlisting>Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8</programlisting>
|
|
|
|
<para>For this reason it is common to see the use of a distinct URI
|
|
for each representation when developing browser based web
|
|
applications.</para>
|
|
</note>
|
|
|
|
<para>To support multiple representations of a resource, Spring provides
|
|
the <classname>ContentNegotiatingViewResolver</classname> to resolve a
|
|
view based on the file extension or <literal>Accept</literal> header of
|
|
the HTTP request. <classname>ContentNegotiatingViewResolver</classname>
|
|
does not perform the view resolution itself but instead delegates to a
|
|
list of view resolvers that you specify through the bean property
|
|
<literal>ViewResolvers</literal>.<!--A human has to specify this list of resolvers, right? See example below.--></para>
|
|
|
|
<para>The <classname>ContentNegotiatingViewResolver</classname> selects
|
|
an appropriate <classname>View</classname> to handle the request by
|
|
comparing the request media type(s) with the media type (also known as
|
|
<literal>Content-Type</literal>) supported by the
|
|
<classname>View</classname> associated with each of its
|
|
<classname>ViewResolvers</classname>. The first
|
|
<classname>View</classname> in the list that has a compatible
|
|
<literal>Content-Type</literal> returns the representation to the
|
|
client. If a compatible view cannot be supplied by the
|
|
<classname>ViewResolver</classname> chain, then the list of views
|
|
specified through the <literal>DefaultViews</literal> property will be
|
|
consulted. This latter option is appropriate for singleton
|
|
<classname>Views</classname> that can render an appropriate
|
|
representation of the current resource regardless of the logical view
|
|
name. The <literal>Accept</literal> header may include wildcards, for
|
|
example text/*, in which case a <classname>View</classname> whose
|
|
Content-Type was text/xml is a compatible match.</para>
|
|
|
|
<para>To support the resolution of a view based on a file extension, use
|
|
the <classname>ContentNegotiatingViewResolver </classname>bean property
|
|
<literal>mediaTypes</literal> to specify a mapping of file extensions to
|
|
media types. For more information on the algorithm used to determine the
|
|
request media type, refer to the API documentation for
|
|
<classname>ContentNegotiatingViewResolver</classname>.</para>
|
|
|
|
<para>Here is an example configuration of a
|
|
<classname>ContentNegotiatingViewResolver:</classname></para>
|
|
|
|
<programlisting language="xml"><bean class="org.springframework.web.servlet.view.ContentNegotiatingViewResolver">
|
|
<property name="mediaTypes">
|
|
<map>
|
|
<entry key="atom" value="application/atom+xml"/>
|
|
<entry key="html" value="text/html"/>
|
|
<entry key="json" value="application/json"/>
|
|
</map>
|
|
</property>
|
|
<property name="viewResolvers">
|
|
<list>
|
|
<bean class="org.springframework.web.servlet.view.BeanNameViewResolver"/>
|
|
<bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
|
|
<property name="prefix" value="/WEB-INF/jsp/"/>
|
|
<property name="suffix" value=".jsp"/>
|
|
</bean>
|
|
</list>
|
|
</property>
|
|
<property name="defaultViews">
|
|
<list>
|
|
<bean class="org.springframework.web.servlet.view.json.MappingJacksonJsonView" />
|
|
</list>
|
|
</property>
|
|
</bean>
|
|
|
|
|
|
<bean id="content" class="com.springsource.samples.rest.SampleContentAtomView"/></programlisting>
|
|
|
|
<para>The <classname>InternalResourceViewResolver</classname> handles
|
|
the translation of view names and JSP pages, while the
|
|
<classname>BeanNameViewResolver</classname> returns a view based on the
|
|
name of a bean. (See "<link
|
|
linkend="mvc-viewresolver-resolver">Resolving views with the
|
|
ViewResolver interface</link>" for more details on how Spring looks up
|
|
and instantiates a view.) In this example, the
|
|
<literal>content</literal> bean is a class that inherits from
|
|
<classname>AbstractAtomFeedView</classname>, which returns an Atom RSS
|
|
feed. For more information on creating an Atom Feed representation, see
|
|
the section Atom Views.<!--Need a correct link or x-ref re the preceding sentence.I couldn't find an "Atom Views" section.--></para>
|
|
|
|
<para>In the above configuration, if a request is made with an
|
|
<literal>.html</literal> extension, the view resolver looks for a view
|
|
that matches the <literal>text/html</literal> media type. The
|
|
<classname>InternalResourceViewResolver</classname> provides the
|
|
matching view for <literal>text/html</literal>. If the request is made
|
|
with the file extension <literal>.atom</literal>, the view resolver
|
|
looks for a view that matches the
|
|
<literal>application/atom+xml</literal> media type. This view is
|
|
provided by the <classname>BeanNameViewResolver</classname> that maps to
|
|
the <classname>SampleContentAtomView</classname> if the view name
|
|
returned is <classname>content</classname>. If the request is made with
|
|
the file extension <literal>.json</literal>, the
|
|
<classname>MappingJacksonJsonView</classname> instance from the
|
|
<literal>DefaultViews</literal> list will be selected regardless of the
|
|
view name. Alternatively, client requests can be made without a file
|
|
extension but with the <literal>Accept</literal> header set to the
|
|
preferred media-type, and the same resolution of request to views would
|
|
occur.<!--Can you reword preceding sentence? I don't follow it.--></para>
|
|
|
|
<note>
|
|
<para>If <classname>ContentNegotiatingViewResolver</classname>'s list
|
|
of ViewResolvers is not configured explicitly, it automatically uses
|
|
any ViewResolvers defined in the application context.</para>
|
|
</note>
|
|
|
|
<para>The corresponding controller code that returns an Atom RSS feed
|
|
for a URI of the form <literal>http://localhost/content.atom</literal>
|
|
or <literal>http://localhost/content</literal> with an
|
|
<literal>Accept</literal> header of application/atom+xml is shown
|
|
below.</para>
|
|
|
|
<programlisting language="java">@Controller
|
|
public class ContentController {
|
|
|
|
private List<SampleContent> contentList = new ArrayList<SampleContent>();
|
|
|
|
@RequestMapping(value="/content", method=RequestMethod.GET)
|
|
public ModelAndView getContent() {
|
|
ModelAndView mav = new ModelAndView();
|
|
mav.setViewName("content");
|
|
mav.addObject("sampleContentList", contentList);
|
|
return mav;
|
|
}
|
|
|
|
}</programlisting>
|
|
</section>
|
|
</section>
|
|
|
|
<section id="mvc-localeresolver">
|
|
<title>Using locales</title>
|
|
|
|
<para>Most parts of Spring's architecture support internationalization,
|
|
just as the Spring web MVC framework does.
|
|
<classname>DispatcherServlet</classname> enables you to automatically
|
|
resolve messages using the client's locale. This is done with
|
|
<interfacename>LocaleResolver</interfacename> objects.</para>
|
|
|
|
<para>When a request comes in, the
|
|
<classname>DispatcherServlet</classname> looks for a locale resolver, and
|
|
if it finds one it tries to use it to set the locale. Using the
|
|
<literal>RequestContext.getLocale()</literal> method, you can always
|
|
retrieve the locale that was resolved by the locale resolver.</para>
|
|
|
|
<para>In addition to automatic locale resolution, you can also attach an
|
|
interceptor to the handler mapping (see <xref
|
|
linkend="mvc-handlermapping-interceptor" /> for more information on
|
|
handler mapping interceptors) to change the locale under specific
|
|
circumstances, for example, based on a parameter in the request.</para>
|
|
|
|
<para>Locale resolvers and interceptors are defined in the
|
|
<literal>org.springframework.web.servlet.i18n</literal> package and are
|
|
configured in your application context in the normal way. Here is a
|
|
selection of the locale resolvers included in Spring.</para>
|
|
|
|
<section id="mvc-localeresolver-acceptheader">
|
|
<title><classname>AcceptHeaderLocaleResolver</classname></title>
|
|
|
|
<para>This locale resolver inspects the
|
|
<literal>accept-language</literal> header in the request that was sent
|
|
by the client (e.g., a web browser). Usually this header field contains
|
|
the locale of the client's operating system.</para>
|
|
</section>
|
|
|
|
<section id="mvc-localeresolver-cookie">
|
|
<title><classname>CookieLocaleResolver</classname></title>
|
|
|
|
<para>This locale resolver inspects a <classname>Cookie</classname> that
|
|
might exist on the client to see if a locale is specified. If so, it
|
|
uses the specified locale. Using the properties of this locale resolver,
|
|
you can specify the name of the cookie as well as the maximum age. Find
|
|
below an example of defining a
|
|
<classname>CookieLocaleResolver</classname>.</para>
|
|
|
|
<programlisting language="xml"><bean id="localeResolver" class="org.springframework.web.servlet.i18n.CookieLocaleResolver">
|
|
|
|
<property name="cookieName" value="clientlanguage"/>
|
|
|
|
<lineannotation><!-- in seconds. If set to <literal>-1</literal>, the cookie is not persisted (deleted when browser shuts down) --></lineannotation>
|
|
<property name="cookieMaxAge" value="100000">
|
|
|
|
</bean></programlisting>
|
|
|
|
<table id="mvc-cookie-locale-resolver-props-tbl">
|
|
<title><classname>CookieLocaleResolver</classname> properties</title>
|
|
|
|
<tgroup cols="3">
|
|
<colspec colname="c1" colwidth="1*" />
|
|
|
|
<colspec colname="c2" colwidth="1*" />
|
|
|
|
<colspec colname="c3" colwidth="3*" />
|
|
|
|
<thead>
|
|
<row>
|
|
<entry>Property</entry>
|
|
|
|
<entry>Default</entry>
|
|
|
|
<entry>Description</entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry>cookieName</entry>
|
|
|
|
<entry>classname + LOCALE</entry>
|
|
|
|
<entry>The name of the cookie</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry>cookieMaxAge</entry>
|
|
|
|
<entry>Integer.MAX_INT</entry>
|
|
|
|
<entry>The maximum time a cookie will stay persistent on the
|
|
client. If -1 is specified, the cookie will not be persisted; it
|
|
will only be available until the client shuts down his or her
|
|
browser.</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry>cookiePath</entry>
|
|
|
|
<entry>/</entry>
|
|
|
|
<entry>Limits the visibility of the cookie to a certain part of
|
|
your site. When cookiePath is specified, the cookie will only be
|
|
visible to that path and the paths below it.</entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
</section>
|
|
|
|
<section id="mvc-localeresolver-session">
|
|
<title><classname>SessionLocaleResolver</classname></title>
|
|
|
|
<para>The <classname>SessionLocaleResolver</classname> allows you to
|
|
retrieve locales from the session that might be associated with the
|
|
user's request.<!--Aren't you missing some information and example? This section has only one sentence.--></para>
|
|
</section>
|
|
|
|
<section id="mvc-localeresolver-interceptor">
|
|
<title><classname>LocaleChangeInterceptor</classname></title>
|
|
|
|
<para>You can enable changing of locales by adding the
|
|
<classname>LocaleChangeInterceptor</classname> to one of the handler
|
|
mappings (see <xref linkend="mvc-handlermapping" />). It will detect a
|
|
parameter in the request and change the locale. It calls
|
|
<literal>setLocale()</literal> on the
|
|
<interfacename>LocaleResolver</interfacename> that also exists in the
|
|
context. The following example shows that calls to all
|
|
<literal>*.view</literal> resources containing a parameter named
|
|
<literal>siteLanguage</literal> will now change the locale. So, for
|
|
example, a request for the following URL,
|
|
<literal>http://www.sf.net/home.view?siteLanguage=nl</literal> will
|
|
change the site language to Dutch.</para>
|
|
|
|
<programlisting language="xml"><bean id="localeChangeInterceptor"
|
|
class="org.springframework.web.servlet.i18n.LocaleChangeInterceptor">
|
|
<property name="paramName" value="siteLanguage"/>
|
|
</bean>
|
|
|
|
<bean id="localeResolver"
|
|
class="org.springframework.web.servlet.i18n.CookieLocaleResolver"/>
|
|
|
|
<bean id="urlMapping"
|
|
class="org.springframework.web.servlet.handler.SimpleUrlHandlerMapping">
|
|
<property name="interceptors">
|
|
<list>
|
|
<ref bean="localeChangeInterceptor"/>
|
|
</list>
|
|
</property>
|
|
<property name="mappings">
|
|
<value>/**/*.view=someController</value>
|
|
</property>
|
|
</bean></programlisting>
|
|
</section>
|
|
</section>
|
|
|
|
<section id="mvc-themeresolver">
|
|
<title>Using themes</title>
|
|
|
|
<section id="mvc-themeresolver-introduction">
|
|
<title>Overview of themes</title>
|
|
|
|
<para>You can apply Spring Web MVC framework themes to set the overall
|
|
look-and-feel of your application, thereby enhancing user experience. A
|
|
theme is a collection of static resources, typically style sheets and
|
|
images, that affect the visual style of the application.</para>
|
|
</section>
|
|
|
|
<section id="mvc-themeresolver-defining">
|
|
<title>Defining themes</title>
|
|
|
|
<para>To use themes in your web application, you must set up an
|
|
implementation of the
|
|
<interfacename>org.springframework.ui.context.ThemeSource</interfacename>
|
|
interface. The <interfacename>WebApplicationContext</interfacename>
|
|
interface extends <interfacename>ThemeSource</interfacename> but
|
|
delegates its responsibilities to a dedicated implementation. By default
|
|
the delegate will be an
|
|
<classname>org.springframework.ui.context.support.ResourceBundleThemeSource</classname>
|
|
implementation that loads properties files from the root of the
|
|
classpath. To use a custom <interfacename>ThemeSource</interfacename>
|
|
implementation or to configure the base name prefix of the
|
|
<classname>ResourceBundleThemeSource</classname>, you can register a
|
|
bean in the application context with the reserved name
|
|
<classname>themeSource</classname>. The web application context
|
|
automatically detects a bean with that name and uses it.</para>
|
|
|
|
<para>When using the <classname>ResourceBundleThemeSource</classname>, a
|
|
theme is defined in a simple properties file. <!--Revise preceding sentence to clarify: To use ResourceBundleThemeSource, you define a theme in a properties file? OR do you mean a theme--><!--is already defined in a simple properties file for use with ResourceBundleThemeSource?-->The
|
|
properties file lists the resources that make up the theme. Here is an
|
|
example:<!--Is this an example of what a human enters? If not, why is it referred to as an example, if this is exact code already provided?--></para>
|
|
|
|
<programlisting>styleSheet=/themes/cool/style.css
|
|
background=/themes/cool/img/coolBg.jpg</programlisting>
|
|
|
|
<para>The keys of the properties are the names that refer to the themed
|
|
elements from view code. For a JSP, you typically do this using the
|
|
<literal>spring:theme</literal> custom tag, which is very similar to the
|
|
<literal>spring:message</literal> tag. The following JSP fragment uses
|
|
the theme defined in the previous example to customize the look and
|
|
feel:</para>
|
|
|
|
<programlisting language="xml"><%@ taglib prefix="spring" uri="http://www.springframework.org/tags"%>
|
|
<html>
|
|
<head>
|
|
<link rel="stylesheet" href="<spring:theme code='styleSheet'/>" type="text/css"/>
|
|
</head>
|
|
<body style="background=<spring:theme code='background'/>">
|
|
...
|
|
</body>
|
|
</html></programlisting>
|
|
|
|
<para>By default, the <classname>ResourceBundleThemeSource</classname>
|
|
uses an empty base name prefix. As a result, the properties files are
|
|
loaded from the root of the classpath. Thus you would put the
|
|
<literal>cool.properties</literal> theme definition in a directory at
|
|
the root of the classpath, for example, in
|
|
<literal>/WEB-INF/classes</literal>. The
|
|
<classname>ResourceBundleThemeSource</classname> uses the standard Java
|
|
resource bundle loading mechanism, allowing for full
|
|
internationalization of themes. For example, we could have a
|
|
<literal>/WEB-INF/classes/cool_nl.properties</literal> that references a
|
|
special background image with Dutch text on it.</para>
|
|
</section>
|
|
|
|
<section id="mvc-themeresolver-resolving">
|
|
<title>Theme resolvers</title>
|
|
|
|
<para>After you define themes, as in the preceding section, you decide
|
|
which theme to use. The <classname>DispatcherServlet</classname> will
|
|
look for a bean named <classname>themeResolver</classname> to find out
|
|
which <interfacename>ThemeResolver</interfacename> implementation to
|
|
use. A theme resolver works in much the same way as a
|
|
<interfacename>LocaleResolver</interfacename>. It detects the theme to
|
|
use for a particular request and can also alter the request's theme. The
|
|
following theme resolvers are provided by Spring:</para>
|
|
|
|
<table id="mvc-theme-resolver-impls-tbl">
|
|
<title><interfacename>ThemeResolver</interfacename>
|
|
implementations</title>
|
|
|
|
<tgroup cols="2">
|
|
<colspec colname="c1" colwidth="1*" />
|
|
|
|
<colspec colname="c3" colwidth="3*" />
|
|
|
|
<thead>
|
|
<row>
|
|
<entry>Class</entry>
|
|
|
|
<entry>Description</entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry><classname>FixedThemeResolver</classname></entry>
|
|
|
|
<entry>Selects a fixed theme, set using the
|
|
<classname>defaultThemeName</classname> property.</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><classname>SessionThemeResolver</classname></entry>
|
|
|
|
<entry>The theme is maintained in the user's HTTP session. It
|
|
only needs to be set once for each session, but is not persisted
|
|
between sessions.</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><classname>CookieThemeResolver</classname></entry>
|
|
|
|
<entry>The selected theme is stored in a cookie on the
|
|
client.</entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>Spring also provides a
|
|
<classname>ThemeChangeInterceptor</classname> that allows theme changes
|
|
on every request with a simple request parameter.<!--Do you need more info or an example re preceding sentence?--></para>
|
|
</section>
|
|
</section>
|
|
|
|
<section id="mvc-multipart">
|
|
<title>Spring's multipart (fileupload) support</title>
|
|
|
|
<section id="mvc-multipart-introduction">
|
|
<title>Introduction</title>
|
|
|
|
<para>Spring's built-in multipart support handles file uploads in web
|
|
applications. You enable this multipart support with pluggable
|
|
<interfacename>MultipartResolver</interfacename> objects, defined in the
|
|
<literal>org.springframework.web.multipart</literal> package. Spring
|
|
provides a <interfacename>MultipartResolver</interfacename> for use with
|
|
<ulink url="http://jakarta.apache.org/commons/fileupload">
|
|
<emphasis>Commons FileUpload</emphasis></ulink>).</para>
|
|
|
|
<para>By default, Spring does no multipart handling, because some
|
|
developers want to handle multiparts themselves. You enable Spring
|
|
multipart handling by adding a multipart resolver to the web
|
|
application's context. Each request is inspected to see if it contains a
|
|
multipart. If no multipart is found, the request continues as expected.
|
|
If a multipart is found in the request, the
|
|
<classname>MultipartResolver</classname> that has been declared in your
|
|
context is used. After that, the multipart attribute in your request is
|
|
treated like any other attribute.</para>
|
|
</section>
|
|
|
|
<section id="mvc-multipart-resolver">
|
|
<title>Using the
|
|
<interfacename>MultipartResolver</interfacename></title>
|
|
|
|
<para>The following example shows how to use the
|
|
<classname>CommonsMultipartResolver</classname>:</para>
|
|
|
|
<programlisting language="xml"><bean id="multipartResolver"
|
|
class="org.springframework.web.multipart.commons.CommonsMultipartResolver">
|
|
|
|
<lineannotation><!-- one of the properties available; the maximum file size in bytes --></lineannotation>
|
|
<property name="maxUploadSize" value="100000"/>
|
|
</bean></programlisting>
|
|
|
|
<para>Of course you also need to put the appropriate jars in your
|
|
classpath for the multipart resolver to work. In the case of the
|
|
<classname>CommonsMultipartResolver</classname>, you need to use
|
|
<literal>commons-fileupload.jar</literal>.</para>
|
|
|
|
<para>When the Spring <classname>DispatcherServlet</classname> detects a
|
|
multi-part request, it activates the resolver that has been declared in
|
|
your context and hands over the request. The resolver then wraps the
|
|
current <classname>HttpServletRequest</classname> into a
|
|
<classname>MultipartHttpServletRequest</classname> that supports
|
|
multipart file uploads. Using the
|
|
<classname>MultipartHttpServletRequest</classname>, you can get
|
|
information about the multiparts contained by this request and actually
|
|
get access to the multipart files themselves in your controllers.</para>
|
|
</section>
|
|
|
|
<section id="mvc-multipart-forms">
|
|
<title>Handling a file upload in a form</title>
|
|
|
|
<para>After the <classname>MultipartResolver</classname> completes its
|
|
job, the request is processed like any other. First, create a form with
|
|
a file input that will allow the user to upload a form. The encoding
|
|
attribute (<literal>enctype="multipart/form-data"</literal>) lets the
|
|
browser know how to encode the form as multipart request:</para>
|
|
|
|
<programlisting language="xml"><html>
|
|
<head>
|
|
<title>Upload a file please</title>
|
|
</head>
|
|
<body>
|
|
<h1>Please upload a file</h1>
|
|
<form method="post" action="/form" enctype="multipart/form-data">
|
|
<input type="text" name="name"/>
|
|
<input type="file" name="file"/>
|
|
<input type="submit"/>
|
|
</form>
|
|
</body>
|
|
</html></programlisting>
|
|
|
|
<para>The next step is to create a controller that handles the file
|
|
upload. This controller is very similar to a <link
|
|
linkend="mvc-ann-controller">normal annotated
|
|
<interfacename>@Controller</interfacename></link>, except that we use
|
|
<classname>MultipartHttpServletRequest</classname> or
|
|
<filename>MultipartFile</filename> in the method parameters:
|
|
<programlisting language="java">@Controller
|
|
public class FileUpoadController {
|
|
|
|
@RequestMapping(value = "/form", method = RequestMethod.POST)
|
|
public String handleFormUpload(@RequestParam("name") String name,
|
|
@RequestParam("file") MultipartFile file) {
|
|
|
|
if (!file.isEmpty()) {
|
|
byte[] bytes = file.getBytes();
|
|
<lineannotation>// store the bytes somewhere</lineannotation>
|
|
return "redirect:uploadSuccess";
|
|
} else {
|
|
return "redirect:uploadFailure";
|
|
}
|
|
}
|
|
|
|
}</programlisting></para>
|
|
|
|
<para>Note how the <interfacename>@RequestParam</interfacename> method
|
|
parameters map to the input elements declared in the form. In this
|
|
example, nothing is done with the <literal>byte[]</literal>, but in
|
|
practice you can save it in a database, store it on the file system, and
|
|
so on.</para>
|
|
|
|
<para>Finally, you will have to declare the controller and the resolver
|
|
in the application context:</para>
|
|
|
|
<programlisting language="xml"><beans>
|
|
<bean id="multipartResolver"
|
|
class="org.springframework.web.multipart.commons.CommonsMultipartResolver"/>
|
|
<lineannotation><!-- Declare explicitly, or use <context:annotation-config/> --></lineannotation>
|
|
<bean id="fileUploadController" class="examples.FileUploadController"/>
|
|
|
|
</beans></programlisting>
|
|
</section>
|
|
</section>
|
|
|
|
<section id="mvc-exceptionhandlers">
|
|
<title>Handling exceptions</title>
|
|
|
|
<section>
|
|
<title
|
|
id="mvc-HandlerExceptionResolver"><interfacename>HandlerExceptionResolver</interfacename></title>
|
|
|
|
<para>Spring <literal>HandlerExceptionResolvers</literal> ease the pain
|
|
of unexpected exceptions that occur while your request is handled by a
|
|
controller that matched the request.
|
|
<literal>HandlerExceptionResolvers</literal> somewhat resemble the
|
|
exception mappings you can define in the web application descriptor
|
|
<literal>web.xml</literal>. However, they provide a more flexible way to
|
|
handle exceptions. They provide information about which handler was
|
|
executing when the exception was thrown. Furthermore, a programmatic way
|
|
of handling exceptions gives you more options for responding
|
|
appropriately before the request is forwarded to another URL (the same
|
|
end result as when you use the servlet specific exception
|
|
mappings).</para>
|
|
|
|
<para>Besides implementing the
|
|
<interfacename>HandlerExceptionResolver</interfacename> interface, which
|
|
is only a matter of implementing the
|
|
<literal>resolveException(Exception, Handler)</literal> method and
|
|
returning a <classname>ModelAndView</classname>, you may also use the
|
|
<classname>SimpleMappingExceptionResolver</classname>. This resolver
|
|
enables you to take the class name of any exception that might be thrown
|
|
and map it to a view name. This is functionally equivalent to the
|
|
exception mapping feature from the Servlet API, but it is also possible
|
|
to implement more finely grained mappings of exceptions from different
|
|
handlers.</para>
|
|
|
|
<para>By default, the <classname>DispatcherServlet</classname> registers
|
|
the <classname>DefaultHandlerExceptionResolver</classname>. This resolver
|
|
handles certain standard Spring MVC exceptions by setting a specific
|
|
response status code:
|
|
<informaltable>
|
|
<tgroup cols="2">
|
|
<thead>
|
|
<row>
|
|
<entry>Exception</entry>
|
|
<entry>HTTP Status Code</entry>
|
|
</row>
|
|
</thead>
|
|
<tbody>
|
|
<row>
|
|
<entry><classname>ConversionNotSupportedException</classname></entry>
|
|
<entry>500 (Internal Server Error)</entry>
|
|
</row>
|
|
<row>
|
|
<entry><classname>HttpMediaTypeNotAcceptableException</classname></entry>
|
|
<entry>406 (Not Acceptable)</entry>
|
|
</row>
|
|
<row>
|
|
<entry><classname>HttpMediaTypeNotSupportedException</classname></entry>
|
|
<entry>415 (Unsupported Media Type)</entry>
|
|
</row>
|
|
<row>
|
|
<entry><classname>HttpMessageNotReadableException</classname></entry>
|
|
<entry>400 (Bad Request)</entry>
|
|
</row>
|
|
<row>
|
|
<entry><classname>HttpMessageNotWritableException</classname></entry>
|
|
<entry>500 (Internal Server Error)</entry>
|
|
</row>
|
|
<row>
|
|
<entry><classname>HttpRequestMethodNotSupportedException</classname></entry>
|
|
<entry>405 (Method Not Allowed)</entry>
|
|
</row>
|
|
<row>
|
|
<entry><classname>MissingServletRequestParameterException</classname></entry>
|
|
<entry>400 (Bad Request)</entry>
|
|
</row>
|
|
<row>
|
|
<entry><classname>NoSuchRequestHandlingMethodException</classname></entry>
|
|
<entry>404 (Not Found)</entry>
|
|
</row>
|
|
<row>
|
|
<entry><classname>TypeMismatchException</classname></entry>
|
|
<entry>400 (Bad Request)</entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</informaltable>
|
|
</para>
|
|
</section>
|
|
|
|
<section id="mvc-ann-exceptionhandler">
|
|
<title><interfacename>@ExceptionHandler<!--Changed this from @ExceptionResolver because text and example say @ExceptionHandler.--></interfacename></title>
|
|
|
|
<para>An alternative to the
|
|
<interfacename>HandlerExceptionResolver</interfacename> interface is the
|
|
<interfacename>@ExceptionHandler</interfacename> annotation. You use the
|
|
<classname>@ExceptionHandler</classname> method annotation within a
|
|
controller to specify which method is invoked when an exception of a
|
|
specific type is thrown during the execution of controller methods. For
|
|
example:</para>
|
|
|
|
<programlisting language="java">@Controller
|
|
public class SimpleController {
|
|
|
|
// other controller method omitted
|
|
|
|
@ExceptionHandler(IOException.class)
|
|
public String handleIOException(IOException ex, HttpServletRequest request) {
|
|
return ClassUtils.getShortName(ex.getClass());
|
|
}
|
|
}</programlisting>
|
|
|
|
<para>will invoke the 'handlerIOException' method when a
|
|
<classname>java.io.IOException</classname> is thrown.</para>
|
|
|
|
<para>The <classname>@ExceptionHandler</classname> value can be set to
|
|
an array of Exception types. If an exception is thrown matches one of
|
|
the types in the list, then the method annotated with the matching
|
|
<classname>@ExceptionHandler</classname> will be invoked. If the
|
|
annotation value is not set then the exception types listed as method
|
|
arguments are used.</para>
|
|
|
|
<para>Much like standard controller methods annotated with a
|
|
<classname>@RequestMapping</classname> annotation, the method arguments
|
|
and return values of <classname>@ExceptionHandler</classname> methods
|
|
are very flexible. For example, the
|
|
<classname>HttpServletRequest</classname> can be accessed in Servlet
|
|
environments and the <classname>PortletRequest</classname> in Portlet
|
|
environments. The return type can be a <classname>String</classname>,
|
|
which is interpreted as a view name or a
|
|
<classname>ModelAndView</classname> object. Refer to the API
|
|
documentation for more details.</para>
|
|
</section>
|
|
</section>
|
|
|
|
<section id="mvc-coc">
|
|
<title>Convention over configuration support</title>
|
|
|
|
<para>For a lot of projects, sticking to established conventions and
|
|
having reasonable defaults is just what they (the projects) need... this
|
|
theme of convention-over-configuration now has explicit support in Spring
|
|
Web MVC. What this means is that if you establish a set of naming
|
|
conventions and suchlike, you can <emphasis>substantially</emphasis> cut
|
|
down on the amount of configuration that is required to set up handler
|
|
mappings, view resolvers, <classname>ModelAndView</classname> instances,
|
|
etc. This is a great boon with regards to rapid prototyping, and can also
|
|
lend a degree of (always good-to-have) consistency across a codebase
|
|
should you choose to move forward with it into production.</para>
|
|
|
|
<para>Convention-over-configuration support addresses the three core areas
|
|
of MVC -- models, views, and controllers.</para>
|
|
|
|
<section id="mvc-coc-ccnhm">
|
|
<title>The Controller
|
|
<classname>ControllerClassNameHandlerMapping</classname></title>
|
|
|
|
<para>The <classname>ControllerClassNameHandlerMapping</classname> class
|
|
is a <interfacename>HandlerMapping</interfacename> implementation that
|
|
uses a convention to determine the mapping between request URLs and the
|
|
<interfacename>Controller</interfacename> instances that are to handle
|
|
those requests.</para>
|
|
|
|
<para>Consider the following simple
|
|
<interfacename>Controller</interfacename> implementation. Take special
|
|
notice of the <emphasis>name</emphasis> of the class.<!--Re preceding sentence, I don't see where the name of the class is discussed in explanation following the example. See my next comment.--></para>
|
|
|
|
<programlisting language="java">public class <emphasis role="bold">ViewShoppingCartController</emphasis> implements Controller {
|
|
|
|
public ModelAndView handleRequest(HttpServletRequest request, HttpServletResponse response) {
|
|
<lineannotation>// the implementation is not hugely important for this example...</lineannotation>
|
|
}
|
|
}</programlisting>
|
|
|
|
<para>Here is a snippet from the attendent Spring Web MVC configuration
|
|
file...</para>
|
|
|
|
<programlisting language="xml"><bean class="org.springframework.web.servlet.mvc.support.ControllerClassNameHandlerMapping"/>
|
|
|
|
<bean id="<emphasis role="bold">viewShoppingCart</emphasis>" class="x.y.z.ViewShoppingCartController">
|
|
<lineannotation><!-- inject dependencies as required... --></lineannotation>
|
|
</bean></programlisting>
|
|
|
|
<para>The <classname>ControllerClassNameHandlerMapping</classname> finds
|
|
all of the various handler (or
|
|
<interfacename>Controller</interfacename>) beans defined in its
|
|
application context and strips <literal>Controller</literal> off the
|
|
name to define its handler mappings. Thus,
|
|
<classname>ViewShoppingCartController</classname> maps to the
|
|
<literal>/viewshoppingcart*</literal> request URL.</para>
|
|
|
|
<para>Let's look at some more examples so that the central idea becomes
|
|
immediately familiar. (Notice all lowercase in the URLs, in contrast to
|
|
camel-cased <interfacename>Controller</interfacename> class
|
|
names.)</para>
|
|
|
|
<itemizedlist>
|
|
<listitem>
|
|
<para><classname>WelcomeController</classname> maps to the
|
|
<literal>/welcome*</literal> request URL</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para><classname>HomeController</classname> maps to the
|
|
<literal>/home*</literal> request URL</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para><classname>IndexController</classname> maps to the
|
|
<literal>/index*</literal> request URL</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para><classname>RegisterController</classname> maps to the
|
|
<literal>/register*</literal> request URL</para>
|
|
</listitem>
|
|
</itemizedlist>
|
|
|
|
<para>In the case of <classname>MultiActionController</classname>
|
|
handler classes, the mappings generated are slightly more complex. The
|
|
<interfacename>Controller</interfacename> names in the following
|
|
examples are assumed to be <classname>MultiActionController</classname>
|
|
implementations:</para>
|
|
|
|
<itemizedlist>
|
|
<listitem>
|
|
<para><classname>AdminController</classname> maps to the
|
|
<literal>/admin</literal><emphasis role="bold">/*</emphasis> request
|
|
URL</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para><classname>CatalogController</classname> maps to the
|
|
<literal>/catalog</literal><emphasis role="bold">/*</emphasis>
|
|
request URL</para>
|
|
</listitem>
|
|
</itemizedlist>
|
|
|
|
<para>If you follow the convention of naming your
|
|
<interfacename>Controller</interfacename> implementations as
|
|
<literal>xxx</literal><emphasis role="bold">Controller</emphasis>, the
|
|
<classname>ControllerClassNameHandlerMapping</classname> saves you the
|
|
tedium of defining and maintaining a potentially
|
|
<emphasis>looooong</emphasis>
|
|
<classname>SimpleUrlHandlerMapping</classname> (or suchlike).</para>
|
|
|
|
<para>The <classname>ControllerClassNameHandlerMapping</classname> class
|
|
extends the <classname>AbstractHandlerMapping</classname> base class so
|
|
you can define <interfacename>HandlerInterceptor</interfacename>
|
|
instances and everything else just as you would with many other
|
|
<interfacename>HandlerMapping</interfacename> implementations.</para>
|
|
</section>
|
|
|
|
<section id="mvc-coc-modelmap">
|
|
<title>The Model <classname>ModelMap</classname>
|
|
(<classname>ModelAndView</classname>)</title>
|
|
|
|
<para>The <classname>ModelMap</classname> class is essentially a
|
|
glorified <interfacename>Map</interfacename> that can make adding
|
|
objects that are to be displayed in (or on) a
|
|
<interfacename>View</interfacename> adhere to a common naming
|
|
convention. Consider the following
|
|
<interfacename>Controller</interfacename> implementation; notice that
|
|
objects are added to the <classname>ModelAndView</classname> without any
|
|
associated name specified.</para>
|
|
|
|
<programlisting language="java">public class DisplayShoppingCartController implements Controller {
|
|
|
|
public ModelAndView handleRequest(HttpServletRequest request, HttpServletResponse response) {
|
|
|
|
List cartItems = <lineannotation>// get a <interfacename>List</interfacename> of <classname>CartItem</classname> objects</lineannotation>
|
|
User user = <lineannotation>// get the <classname>User</classname> doing the shopping</lineannotation>
|
|
|
|
ModelAndView mav = new ModelAndView("displayShoppingCart"); <lineannotation><-- the logical view name</lineannotation>
|
|
|
|
mav.addObject(cartItems); <lineannotation><-- look ma, no name, just the object</lineannotation>
|
|
mav.addObject(user); <lineannotation><-- and again ma!</lineannotation>
|
|
|
|
return mav;
|
|
}
|
|
}</programlisting>
|
|
|
|
<para>The <classname>ModelAndView</classname> class uses a
|
|
<classname>ModelMap</classname> class that is a custom
|
|
<interfacename>Map</interfacename> implementation that automatically
|
|
generates a key for an object when an object is added to it. The
|
|
strategy for determining the name for an added object is, in the case of
|
|
a scalar object such as <classname>User</classname>, to use the short
|
|
class name of the object's class. The following examples are names that
|
|
are generated for scalar objects put into a
|
|
<classname>ModelMap</classname> instance.</para>
|
|
|
|
<itemizedlist>
|
|
<listitem>
|
|
<para>An <classname>x.y.User</classname> instance added will have
|
|
the name <literal>user</literal> generated.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>An <classname>x.y.Registration</classname> instance added will
|
|
have the name <literal>registration</literal> generated.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>An <classname>x.y.Foo</classname> instance added will have the
|
|
name <literal>foo</literal> generated.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>A <classname>java.util.HashMap</classname> instance added will
|
|
have the name <literal>hashMap</literal> generated. You probably
|
|
want to be explicit about the name in this case because
|
|
<literal>hashMap</literal> is less than intuitive.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>Adding <literal>null</literal> will result in an
|
|
<classname>IllegalArgumentException</classname> being thrown. If the
|
|
object (or objects) that you are adding could be
|
|
<literal>null</literal>, then you will also want to be explicit
|
|
about the name.</para>
|
|
</listitem>
|
|
</itemizedlist>
|
|
|
|
<sidebar>
|
|
<title>What, no automatic pluralisation?</title>
|
|
|
|
<para>Spring Web MVC's convention-over-configuration support does not
|
|
support automatic pluralisation. That is, you cannot add a
|
|
<interfacename>List</interfacename> of <classname>Person</classname>
|
|
objects to a <classname>ModelAndView</classname> and have the
|
|
generated name be <classname>people</classname>.</para>
|
|
|
|
<para>This decision was made after some debate, with the
|
|
<quote>Principle of Least Surprise</quote> winning out in the
|
|
end.</para>
|
|
</sidebar>
|
|
|
|
<para>The strategy for generating a name after adding a
|
|
<interfacename>Set</interfacename>, <interfacename>List</interfacename>
|
|
or array object is to peek into the collection, take the short class
|
|
name of the first object in the collection, and use that with
|
|
<literal>List</literal> appended to the name. Some examples will make
|
|
the semantics of name generation for collections clearer...</para>
|
|
|
|
<itemizedlist>
|
|
<listitem>
|
|
<para>An <classname>x.y.User[]</classname> array with one or more
|
|
<classname>x.y.User</classname> elements added will have the name
|
|
<literal>userList</literal> generated.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>An <classname>x.y.Foo[]</classname> array with one or more
|
|
<classname>x.y.User</classname> elements added will have the name
|
|
<literal>fooList</literal> generated.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>A <classname>java.util.ArrayList</classname> with one or more
|
|
<classname>x.y.User</classname> elements added will have the name
|
|
<literal>userList</literal> generated.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>A <classname>java.util.HashSet</classname> with one or more
|
|
<classname>x.y.Foo</classname> elements added will have the name
|
|
<literal>fooList</literal> generated.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>An <emphasis role="bold">empty</emphasis>
|
|
<classname>java.util.ArrayList</classname> will not be added at all
|
|
(in effect, the <methodname>addObject(..)</methodname> call will
|
|
essentially be a no-op).</para>
|
|
</listitem>
|
|
</itemizedlist>
|
|
</section>
|
|
|
|
<section id="mvc-coc-r2vnt">
|
|
<title>The View -
|
|
<interfacename>RequestToViewNameTranslator</interfacename></title>
|
|
|
|
<para>The <interfacename>RequestToViewNameTranslator</interfacename>
|
|
interface determines a logical <interfacename>View</interfacename> name
|
|
when no such logical view name is explicitly supplied. It has just one
|
|
implementation, the
|
|
<classname>DefaultRequestToViewNameTranslator</classname> class.</para>
|
|
|
|
<para>The <classname>DefaultRequestToViewNameTranslator</classname> maps
|
|
request URLs to logical view names, as with this example:</para>
|
|
|
|
<programlisting language="java">public class RegistrationController implements Controller {
|
|
|
|
public ModelAndView handleRequest(HttpServletRequest request, HttpServletResponse response) {
|
|
<lineannotation>// process the request...</lineannotation>
|
|
ModelAndView mav = new ModelAndView();
|
|
<lineannotation>// add <emphasis role="bold">data</emphasis> as necessary to the model...</lineannotation>
|
|
return mav;
|
|
<lineannotation>// notice that no <interfacename>View</interfacename> or logical view name has been set</lineannotation>
|
|
}
|
|
}</programlisting>
|
|
|
|
<programlisting language="xml"><?xml version="1.0" encoding="UTF-8"?>
|
|
<!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN 2.0//EN"
|
|
"http://www.springframework.org/dtd/spring-beans-2.0.dtd">
|
|
<beans>
|
|
|
|
<lineannotation><!-- this bean with the well known name generates view names for us --></lineannotation>
|
|
<bean id="viewNameTranslator" class="org.springframework.web.servlet.view.DefaultRequestToViewNameTranslator"/>
|
|
|
|
<bean class="x.y.RegistrationController">
|
|
<lineannotation><!-- inject dependencies as necessary --></lineannotation>
|
|
</bean>
|
|
|
|
<lineannotation><!-- maps request URLs to Controller names --></lineannotation>
|
|
<bean class="org.springframework.web.servlet.mvc.support.ControllerClassNameHandlerMapping"/>
|
|
|
|
<bean id="viewResolver" class="org.springframework.web.servlet.view.InternalResourceViewResolver">
|
|
<property name="prefix" value="/WEB-INF/jsp/"/>
|
|
<property name="suffix" value=".jsp"/>
|
|
</bean>
|
|
|
|
</beans>
|
|
</programlisting>
|
|
|
|
<para>Notice how in the implementation of the
|
|
<literal>handleRequest(..)</literal> method no
|
|
<interfacename>View</interfacename> or logical view name is ever set on
|
|
the <classname>ModelAndView</classname> that is returned. The
|
|
<classname>DefaultRequestToViewNameTranslator</classname> is tasked with
|
|
generating a <emphasis>logical view name</emphasis> from the URL of the
|
|
request. In the case of the above
|
|
<classname>RegistrationController</classname>, which is used in
|
|
conjunction with the
|
|
<classname>ControllerClassNameHandlerMapping</classname>, a request URL
|
|
of <literal>http://localhost/registration.html</literal> results in a
|
|
logical view name of <literal>registration</literal> being generated by
|
|
the <classname>DefaultRequestToViewNameTranslator</classname>. This
|
|
logical view name is then resolved into the
|
|
<literal>/WEB-INF/jsp/registration.jsp</literal> view by the
|
|
<classname>InternalResourceViewResolver</classname> bean.</para>
|
|
|
|
<tip>
|
|
<para>You do not need to define a
|
|
<classname>DefaultRequestToViewNameTranslator</classname> bean
|
|
explicitly. If you like the default settings of the
|
|
<classname>DefaultRequestToViewNameTranslator</classname>, you can
|
|
rely on the Spring Web MVC <classname>DispatcherServlet</classname> to
|
|
instantiate an instance of this class if one is not explicitly
|
|
configured.</para>
|
|
</tip>
|
|
|
|
<para>Of course, if you need to change the default settings, then you do
|
|
need to configure your own
|
|
<classname>DefaultRequestToViewNameTranslator</classname> bean
|
|
explicitly. Consult the comprehensive Javadoc for the
|
|
<classname>DefaultRequestToViewNameTranslator</classname> class for
|
|
details of the various properties that can be configured.</para>
|
|
</section>
|
|
</section>
|
|
|
|
<section id="mvc-etag">
|
|
<title>ETag support</title>
|
|
|
|
<para>An <ulink url="http://en.wikipedia.org/wiki/HTTP_ETag">ETag</ulink>
|
|
(entity tag) is an HTTP response header returned by an HTTP/1.1 compliant
|
|
web server used to determine change in content at a given URL. It can be
|
|
considered to be the more sophisticated successor to the
|
|
<literal>Last-Modified</literal> header. When a server returns a
|
|
representation with an ETag header, the client can use this header in
|
|
subsequent GETs, in an <literal>If-None-Match</literal> header. If the
|
|
content has not changed, the server returns <literal>304: Not
|
|
Modified</literal>.</para>
|
|
|
|
<para>Support for ETags is provided by the servlet filter
|
|
<classname>ShallowEtagHeaderFilter</classname>. It is a plain Servlet
|
|
Filter, and thus can be used in combination with any web framework. <!--The preceding sentence was a fragment, not a complete sentence. Have I reworded ok?-->The
|
|
<classname>ShallowEtagHeaderFilter</classname> filter creates so-called
|
|
shallow ETags (as opposed to deep ETags, more about that later).<!--Provide xref to deep ETags.-->The
|
|
filter caches the content of the rendered JSP (or other content),
|
|
generates an MD5 hash over that, and returns that as an ETag header in the
|
|
response. The next time a client sends a request for the same resource, it
|
|
uses that hash as the <literal>If-None-Match</literal> value. The filter
|
|
detects this, renders the view again, and compares the two hashes. If they
|
|
are equal, a <literal>304</literal> is returned. This filter will not save
|
|
processing power, as the view is still rendered. The only thing it saves
|
|
is bandwidth, as the rendered response is not sent back over the
|
|
wire.</para>
|
|
|
|
<para>You configure the <classname>ShallowEtagHeaderFilter</classname> in
|
|
<filename>web.xml</filename>:</para>
|
|
|
|
<programlisting language="xml"><filter>
|
|
<filter-name>etagFilter</filter-name>
|
|
<filter-class>org.springframework.web.filter.ShallowEtagHeaderFilter</filter-class>
|
|
</filter>
|
|
|
|
<filter-mapping>
|
|
<filter-name>etagFilter</filter-name>
|
|
<servlet-name>petclinic</servlet-name>
|
|
</filter-mapping></programlisting>
|
|
</section>
|
|
<section id="mvc-config">
|
|
<title>Configuring Spring MVC</title>
|
|
<para>
|
|
Spring 3 introduces a <literal>mvc</literal> XML configuration namespace that simplifies the setup of Spring MVC inside your web application.
|
|
Instead of registering low-level beans such as AnnotationMethodHandlerAdapter, you can simply use the namespace and its higher-level constructs.
|
|
This is generally preferred unless you require finer-grained control of the configuration at the bean level.
|
|
</para>
|
|
<para>
|
|
The mvc namespace consists of three tags: mvc:annotation-driven, mvc:interceptors, and mvc:view-controller.
|
|
Each of these tags is documented below and in the <ulink url="http://static.springsource.org/schema/mvc/spring-mvc-3.0.xsd">XML schema</ulink>.
|
|
</para>
|
|
<section id="mvc-annotation-driven">
|
|
<title>mvc:annotation-driven</title>
|
|
<para>
|
|
This tag registers the DefaultAnnotationHandlerMapping and AnnotationMethodHandlerAdapter beans that are required for Spring MVC to dispatch requests to @Controllers.
|
|
The tag configures those two beans with sensible defaults based on what is present in your classpath.
|
|
The defaults are:
|
|
<orderedlist>
|
|
<listitem>
|
|
<para>
|
|
Support for Spring 3's Type <link linkend="core-convert">ConversionService</link> in addition to JavaBeans PropertyEditors during Data Binding.
|
|
A ConversionService instance produced by the <classname>org.springframework.format.support.FormattingConversionServiceFactoryBean</classname> is used by default.
|
|
This can be overriden by setting the <literal>conversion-service</literal> attribute.
|
|
</para>
|
|
</listitem>
|
|
<listitem>
|
|
<para>
|
|
Support for <link linkend="format">formatting</link> Number fields using the @NumberFormat annotation
|
|
</para>
|
|
</listitem>
|
|
<listitem>
|
|
<para>
|
|
Support for <link linkend="format">formatting</link> Date, Calendar, Long, and Joda Time fields using the @DateTimeFormat annotation, if Joda Time 1.3 or higher is present on the classpath.
|
|
</para>
|
|
</listitem>
|
|
<listitem>
|
|
<para>
|
|
Support for <link linkend="validation-mvc-jsr303">validating</link> @Controller inputs with @Valid, if a JSR-303 Provider is present on the classpath.
|
|
The validation system can be explicitly configured by setting the <literal>validator</literal> attribute.
|
|
</para>
|
|
</listitem>
|
|
<listitem>
|
|
<para>
|
|
HttpMessageConverter support for @RequestBody method parameters and @ResponseBody method return values.
|
|
</para>
|
|
<para>
|
|
This is the complete list of HttpMessageConverters set up by mvc:annotation-driven:
|
|
<itemizedlist>
|
|
<listitem>
|
|
<para><classname>ByteArrayHttpMessageConverter</classname>
|
|
converts byte arrays.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para><classname>StringHttpMessageConverter</classname> converts
|
|
strings.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para><classname>ResourceHttpMessageConverter</classname> converts
|
|
to/from <classname>org.springframework.core.io.Resource</classname>
|
|
for all media types.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para><classname>SourceHttpMessageConverter</classname> converts
|
|
to/from a <classname>javax.xml.transform.Source</classname>.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para><classname>FormHttpMessageConverter</classname> converts
|
|
form data to/from a <classname>MultiValueMap<String, String></classname>.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para><classname>Jaxb2RootElementHttpMessageConverter</classname>
|
|
converts Java objects to/from XML -- added if JAXB2 is present
|
|
on the classpath.
|
|
</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para><classname>MappingJacksonHttpMessageConverter</classname>
|
|
converts to/from JSON -- added if Jackson is present on the classpath.
|
|
</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para><classname>AtomFeedHttpMessageConverter</classname>
|
|
converts Atom feeds -- added if Rome is present on the classpath.
|
|
</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para><classname>RssChannelHttpMessageConverter</classname>
|
|
converts RSS feeds -- added if Rome is present on the classpath.
|
|
</para>
|
|
</listitem>
|
|
</itemizedlist>
|
|
</para>
|
|
<note>
|
|
<para>
|
|
You can provide your own HttpMessageConverters through the
|
|
mvc:message-converters sub-element of mvc:annotation-driven.
|
|
Message converters you provide will take precedence over the
|
|
ones registered by default.
|
|
</para>
|
|
</note>
|
|
</listitem>
|
|
</orderedlist>
|
|
A typical usage is shown below:
|
|
<programlisting language="xml"><![CDATA[
|
|
<?xml version="1.0" encoding="UTF-8"?>
|
|
<beans xmlns="http://www.springframework.org/schema/beans"
|
|
xmlns:mvc="http://www.springframework.org/schema/mvc"
|
|
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
|
|
xsi:schemaLocation="
|
|
http://www.springframework.org/schema/beans
|
|
http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
|
|
http://www.springframework.org/schema/mvc
|
|
http://www.springframework.org/schema/mvc/spring-mvc-3.0.xsd">
|
|
|
|
<!-- JSR-303 support will be detected on classpath and enabled automatically -->
|
|
<mvc:annotation-driven/>
|
|
|
|
</beans>]]>
|
|
</programlisting>
|
|
</para>
|
|
</section>
|
|
<section id="mvc-interceptors">
|
|
<title>mvc:interceptors</title>
|
|
<para>
|
|
This tag allows you to register custom HandlerInterceptors or WebRequestInterceptors that should be applied to all HandlerMapping beans.
|
|
You can also restrict the URL paths specifc interceptors apply to.
|
|
</para>
|
|
<para>
|
|
An example of registering an interceptor applied to all URL paths:
|
|
</para>
|
|
<programlisting language="xml"><![CDATA[
|
|
<mvc:interceptors>
|
|
<bean class="org.springframework.web.servlet.i18n.LocaleChangeInterceptor" />
|
|
</mvc:interceptors>]]>
|
|
</programlisting>
|
|
<para>
|
|
An example of registering an interceptor limited to a specific URL path:
|
|
</para>
|
|
<programlisting language="xml"><![CDATA[
|
|
<mvc:interceptors>
|
|
<mvc:interceptor>
|
|
<mapping path="/secure/*"/>
|
|
<bean class="org.example.SecurityInterceptor" />
|
|
</mvc:interceptor>
|
|
</mvc:interceptors>]]>
|
|
</programlisting>
|
|
</section>
|
|
<section id="mvc-view-controller">
|
|
<title>mvc:view-controller</title>
|
|
<para>
|
|
This tag is a shorcut for defining a <classname>ParameterizableViewController</classname> that immediately forwards to a view when invoked.
|
|
Use it in static cases when there is no Java Controller logic to execute before the view generates the response.
|
|
</para>
|
|
<para>
|
|
An example of view-controller that forwards to a home page is shown below:
|
|
</para>
|
|
<programlisting language="xml"><![CDATA[
|
|
<mvc:view-controller path="/" view-name="home"/>]]>
|
|
</programlisting>
|
|
</section>
|
|
<section id="mvc-static-resources">
|
|
<title>mvc:resources</title>
|
|
<para>
|
|
This tag allows static resource requests following a particular URL pattern to be served by a <classname>ResourceHttpRequestHandler</classname> from
|
|
any of a list of <classname>Resource</classname> locations. This provides a convenient way to serve static resources from locations other than the
|
|
web application root, including locations on the classpath. The <code>cache-period</code> property may be used to set far future expiration headers
|
|
(1 year is the recommendation of optimization tools such as Page Speed and YSlow) so that they will be more efficiently utilized by the client. The handler
|
|
also properly evaluates the <code>Last-Modified</code> header (if present) so that a <code>304</code> status code will be returned as appropriate, avoiding
|
|
unnecessary overhead for resources that are already cached by the client. For example, to serve resource requests with a URL pattern of
|
|
<code>/resources/**</code> from a <code>public-resources</code> directory within the web application root, the tag would be used as follows:
|
|
</para>
|
|
<programlisting language="xml"><![CDATA[
|
|
<mvc:resources mapping="/resources/**" location="/public-resources/"/>]]>
|
|
</programlisting>
|
|
<para>
|
|
To serve these resources with a 1-year future expiration to ensure maximum use of the browser cache and a reduction in HTTP requests made by the browser:
|
|
</para>
|
|
<programlisting language="xml"><![CDATA[
|
|
<mvc:resources mapping="/resources/**" location="/public-resources/" cache-period="31556926"/>]]>
|
|
</programlisting>
|
|
<para>
|
|
The <code>mapping</code> attribute must be an Ant pattern that can be used by <classname>SimpleUrlHandlerMapping</classname>, and the <code>location</code>
|
|
attribute must specify one or more valid resource directory locations. Multiple resource locations may be specified using a comma-seperated list of values.
|
|
The locations specified will be checked in the specified order for the presence of the resource for any given request. For example, to enable the serving
|
|
of resources from both the web application root and from a known path of <code>/META-INF/public-web-resources/</code> in any jar on the classpath, the tag
|
|
would be specified as:
|
|
</para>
|
|
<programlisting language="xml"><![CDATA[
|
|
<mvc:resources mapping="/resources/**" location="/, classpath:/META-INF/public-web-resources/"/>]]>
|
|
</programlisting>
|
|
<para>
|
|
When serving resources that may change when a new version of the application is deployed, it is recommended that you incorporate a version string into the
|
|
mapping pattern used to request the resources, so that you may force clients to request the newly deployed version of your application's resources. Such a
|
|
version string can be parameterized and accessed using SpEL so that it may be easily managed in a single place when deploying new versions.
|
|
</para>
|
|
<para>
|
|
As an example, let's consider an application that uses a performance-optimized custom build (as recommended) of the Dojo JavaScript library in production, and that the build is generally
|
|
deployed within the web application at a path of <code>/public-resources/dojo/dojo.js</code>. Since different parts of Dojo may be incorporated into the
|
|
custom build for each new version of the application, the client web browsers need to be forced to re-download that custom-built <code>dojo.js</code> resource
|
|
any time a new version of the application is deployed. A simple way to achieve this would be to manage the version of the application in a properties file,
|
|
such as:
|
|
</para>
|
|
<programlisting><![CDATA[
|
|
application.version=1.0.0]]>
|
|
</programlisting>
|
|
<para>
|
|
and then to make the properties file's values accessible to SpEL as a bean using the <code>util:properties</code> tag:
|
|
</para>
|
|
<programlisting language="xml"><![CDATA[
|
|
<util:properties id="applicationProps" location="/WEB-INF/spring/application.properties"/>]]>
|
|
</programlisting>
|
|
<para>
|
|
With the application version now accessible via SpEL, we can incorporate this into the use of the <code>resources</code> tag:
|
|
</para>
|
|
<programlisting language="xml"><![CDATA[
|
|
<mvc:resources mapping="/resources-#{applicationProps['application.version']}/**" location="/public-resources/"/>]]>
|
|
</programlisting>
|
|
<para>
|
|
and finally, to request the resource with the proper URL, we can take advantage of the Spring JSP tags:
|
|
</para>
|
|
<programlisting language="xml"><![CDATA[
|
|
<spring:eval expression="@applicationProps['application.version']" var="applicationVersion"/>
|
|
|
|
<spring:url value="/resources-{applicationVersion}" var="resourceUrl">
|
|
<spring:param name="applicationVersion" value="${applicationVersion}"/>
|
|
</spring:url>
|
|
|
|
<script src="${resourceUrl}/dojo/dojo.js" type="text/javascript"> </script>]]>
|
|
</programlisting>
|
|
</section>
|
|
<section id="mvc-default-servlet-handler">
|
|
<title>mvc:default-servlet-handler</title>
|
|
<para>
|
|
This tag allows for mapping the <code>DispatcherServlet</code> to "/" (thus overriding the mapping of the container's default Servlet),
|
|
while still allowing static resource requests to be handled by the container's default Servlet. It configures a
|
|
<code>DefaultServletHttpRequestHandler</code> with a URL mapping (given a lowest precedence order) of "/**". This handler will
|
|
forward all requests to the default Servlet. To enable this feature using the default setup, simply include the tag in the form:
|
|
</para>
|
|
<programlisting language="xml"><![CDATA[
|
|
<mvc:default-servlet-handler/>]]>
|
|
</programlisting>
|
|
<para>
|
|
The caveat to overriding the "/" Servlet mapping is that the <code>RequestDispatcher</code> for the default Servlet must be
|
|
retrieved by name rather than by path. The <code>DefaultServletHttpRequestHandler</code> will attempt to auto-detect the default
|
|
Servlet for the container at startup time, using a list of known names for most of the major Servlet containers (including Tomcat,
|
|
Jetty, Glassfish, JBoss, Resin, WebLogic, and WebSphere). If the default Servlet has been custom configured
|
|
with a different name, or if a different Servlet container is being used where the default Servlet name is unknown, then the
|
|
default Servlet's name must be explicitly provided as in the following example:
|
|
</para>
|
|
<programlisting language="xml"><![CDATA[
|
|
<mvc:default-servlet-handler default-servlet-name="myCustomDefaultServlet"/>]]>
|
|
</programlisting>
|
|
</section>
|
|
</section>
|
|
<section id="mvc-resources">
|
|
<title>More Spring Web MVC Resources</title>
|
|
|
|
<para>See the following links and pointers for more resources about Spring
|
|
Web MVC:</para>
|
|
|
|
<itemizedlist>
|
|
<listitem>
|
|
<para>
|
|
There are many excellent articles and tutorials that show how to build web applications with Spring MVC.
|
|
Read them at the <ulink url="http://www.springsource.org/documentation">Spring Documentation</ulink> page.
|
|
</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para><quote>Expert Spring Web MVC and Web Flow</quote> by Seth Ladd
|
|
and others (published by Apress) is an excellent hard copy source of
|
|
Spring Web MVC goodness.</para>
|
|
</listitem>
|
|
</itemizedlist>
|
|
</section>
|
|
</chapter>
|