Document @Fallback alongside Primary in the reference docs and @Bean Javadoc

Closes gh-36439

framework-docs/modules/ROOT/pages/core/beans/annotation-config/autowired-qualifiers.adoc

@@ -151,17 +151,17 @@ injected into a `Set<MovieCatalog>` annotated with `@Qualifier("action")`.
 [TIP]
 ====
 Letting qualifier values select against target bean names, within the type-matching
-candidates, does not require a `@Qualifier` annotation at the injection point.
-If there is no other resolution indicator (such as a qualifier or a primary marker),
-for a non-unique dependency situation, Spring matches the injection point name
-(that is, the field name or parameter name) against the target bean names and chooses
-the same-named candidate, if any (either by bean name or by associated alias).
+candidates, does not require a `@Qualifier` annotation at the injection point. If there
+is no other resolution indicator (such as a qualifier, a primary marker, or a fallback
+marker), for a non-unique dependency situation, Spring matches the injection point name
+(that is, the field name or parameter name) against the target bean names and chooses the
+same-named candidate, if any (either by bean name or by associated alias).
 
-Since version 6.1, this requires the `-parameters` Java compiler flag to be present.
-As of 6.2, the container applies fast shortcut resolution for bean name matches,
-bypassing the full type matching algorithm when the parameter name matches the
-bean name and no type, qualifier or primary conditions override the match. It is
-therefore recommendable for your parameter names to match the target bean names.
+Since version 6.1, this requires the `-parameters` Java compiler flag to be present. As
+of 6.2, the container applies fast shortcut resolution for bean name matches, bypassing
+the full type matching algorithm when the parameter name matches the bean name and no
+type, qualifier, primary, or fallback conditions override the match. It is therefore
+recommendable for your parameter names to match the target bean names.
 ====
 
 As an alternative for injection by name, consider the JSR-250 `@Resource` annotation

framework-docs/modules/ROOT/pages/core/beans/annotation-config/autowired.adoc

@@ -309,7 +309,8 @@ set of multiple matches for the specific bean type (as returned by the factory m
 
 Note that the standard `jakarta.annotation.Priority` annotation is not available at the
 `@Bean` level, since it cannot be declared on methods. Its semantics can be modeled
-through `@Order` values in combination with `@Primary` on a single bean for each type.
+through `@Order` values in combination with `@Primary` or `@Fallback` on a single bean
+for each type.
 ====
 
 Even typed `Map` instances can be autowired as long as the expected key type is `String`.

framework-docs/modules/ROOT/pages/core/beans/annotation-config/custom-autowire-configurer.adoc

@@ -27,4 +27,5 @@ with the `CustomAutowireConfigurer`
 
 When multiple beans qualify as autowire candidates, the determination of a "`primary`" is
 as follows: If exactly one bean definition among the candidates has a `primary`
-attribute set to `true`, it is selected.
+attribute set to `true`, it is selected. For annotation-based configuration, see
+xref:core/beans/annotation-config/autowired-primary.adoc[Fine-tuning with `@Primary` or `@Fallback`].

framework-docs/modules/ROOT/pages/web/webflux/config.adoc

@@ -251,7 +251,8 @@ Kotlin::
 ======
 
 TIP: If you need to have a `LocalValidatorFactoryBean` injected somewhere, create a bean and
-mark it with `@Primary` in order to avoid conflict with the one declared in the MVC config.
+mark it with `@Primary`, or mark the one declared in the MVC config with `@Fallback`, in
+order to avoid conflict.
 
 
 [[webflux-config-content-negotiation]]

framework-docs/modules/ROOT/pages/web/webmvc/mvc-config/validation.adoc

@@ -19,4 +19,5 @@ example shows:
 include-code::./MyController[tag=snippet,indent=0]
 
 TIP: If you need to have a `LocalValidatorFactoryBean` injected somewhere, create a bean and
-mark it with `@Primary` in order to avoid conflict with the one declared in the MVC configuration.
+mark it with `@Primary`, or mark the one declared in the MVC configuration with
+`@Fallback`, in order to avoid conflict.

spring-context/src/main/java/org/springframework/context/annotation/Bean.java

@@ -57,11 +57,11 @@ import org.springframework.core.annotation.AliasFor;
  *     return obj;
  * }</pre>
  *
- * <h3>Profile, Scope, Lazy, DependsOn, Primary, Order</h3>
+ * <h3>Profile, Scope, Lazy, DependsOn, Primary, Fallback, Order</h3>
  *
  * <p>Note that the {@code @Bean} annotation does not provide attributes for profile,
- * scope, lazy, depends-on or primary. Rather, it should be used in conjunction with
- * {@link Scope @Scope}, {@link Lazy @Lazy}, {@link DependsOn @DependsOn} and
+ * scope, lazy, depends-on, or primary. Rather, it should be used in conjunction with
+ * {@link Scope @Scope}, {@link Lazy @Lazy}, {@link DependsOn @DependsOn}, and
  * {@link Primary @Primary} annotations to declare those semantics. For example:
  *
  * <pre class="code">
@@ -82,6 +82,9 @@ import org.springframework.core.annotation.AliasFor;
  * through direct references, which is typically helpful for singleton startup.
  * {@code @Primary} is a mechanism to resolve ambiguity at the injection point level
  * if a single target component needs to be injected but several beans match by type.
+ * {@code @Fallback} marks a bean as a fallback candidate in such scenarios; if all
+ * beans but one among multiple matching candidates are marked as fallback, the
+ * remaining bean will be selected.
  *
  * <p>Additionally, {@code @Bean} methods may also declare qualifier annotations
  * and {@link org.springframework.core.annotation.Order @Order} values, to be
@@ -97,8 +100,8 @@ import org.springframework.core.annotation.AliasFor;
  * orthogonal concern determined by dependency relationships and {@code @DependsOn}
  * declarations as mentioned above. Also, {@link jakarta.annotation.Priority} is not
  * available at this level since it cannot be declared on methods; its semantics can
- * be modeled through {@code @Order} values in combination with {@code @Primary} on
- * a single bean per type.
+ * be modeled through {@code @Order} values in combination with {@code @Primary} or
+ * {@code @Fallback} on a single bean per type.
  *
  * <h3>{@code @Bean} Methods in {@code @Configuration} Classes</h3>
  *
@@ -230,6 +233,7 @@ import org.springframework.core.annotation.AliasFor;
  * @see DependsOn
  * @see Lazy
  * @see Primary
+ * @see Fallback
  * @see org.springframework.stereotype.Component
  * @see org.springframework.beans.factory.annotation.Autowired
  * @see org.springframework.beans.factory.annotation.Value