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Andy Wilkinson
2109559f37
Previously, the Actuator’s endpoints did not specify a produces attribute on their request mappings. With Jackson’s XML binding on the classpath, this would lead to requests made by a browser receiving application/xml responses (due to the Accept header indicating that application/xml is preferred). This was problematic as some of the response payloads were not legal xml. Problems included XML tags beginning with ‘\’ or containing ‘#’. This commit updates the endpoints to specify that they produce application/json. The environment and metrics endpoints have also been updated so that always return a JSON object, even when they are returning a single entry. This consistency avoids problems where clients may not consider a single scalar value to be legal JSON. Closes gh-2449
= Spring Boot - Actuator
Spring Boot Actuator includes a number of additional features to help you monitor and
manage your application when it's pushed to production. You can choose to manage and
monitor your application using HTTP endpoints, with JMX or even by remote shell (SSH or
Telnet). Auditing, health and metrics gathering can be automatically applied to your
application. The
http://docs.spring.io/spring-boot/docs/current/reference/htmlsingle/#production-ready[user guide]
covers the features in more detail.
== Enabling the Actuator
The simplest way to enable the features is to add a dependency to the
`spring-boot-starter-actuator` "`Starter POM`". To add the actuator to a Maven based
project, add the following "`starter`" dependency:
[source,xml,indent=0]
----
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-actuator</artifactId>
</dependency>
</dependencies>
----
For Gradle, use the declaration:
[indent=0]
----
dependencies {
compile("org.springframework.boot:spring-boot-starter-actuator")
}
----
== Features
* **Endpoints** Actuator endpoints allow you to monitor and interact with your
application. Spring Boot includes a number of built-in endpoints and you can also add
your own. For example the `health` endpoint provides basic application health
information. Run up a basic application and look at `/health` (and see `/mappings` for
a list of other HTTP endpoints).
* **Metrics** Spring Boot Actuator includes a metrics service with "`gauge`" and
"`counter`" support. A "`gauge`" records a single value; and a "`counter`" records a
delta (an increment or decrement). Metrics for all HTTP requests are automatically
recorded, so if you hit the `metrics` endpoint should see a sensible response.
* **Audit** Spring Boot Actuator has a flexible audit framework that will publish events
to an `AuditService`. Once Spring Security is in play it automatically publishes
authentication events by default. This can be very useful for reporting, and also to
implement a lock-out policy based on authentication failures.
* **Process Monitoring** In Spring Boot Actuator you can find `ApplicationPidListener`
which creates a file containing the application PID (by default in the application
directory with a file name of `application.pid`).