Reference documentation for @fallback

See gh-26241

Author: jhoeller

Diff for: framework-docs/modules/ROOT/pages/core/beans/annotation-config/autowired-primary.adoc

@@ -1,5 +1,5 @@
 [[beans-autowired-annotation-primary]]
-= Fine-tuning Annotation-based Autowiring with `@Primary`
+= Fine-tuning Annotation-based Autowiring with `@Primary` or `@Fallback`
 
 Because autowiring by type may lead to multiple candidates, it is often necessary to have
 more control over the selection process. One way to accomplish this is with Spring's
@@ -50,8 +50,51 @@ Kotlin::
 ----
 ======
 
-With the preceding configuration, the following `MovieRecommender` is autowired with the
-`firstMovieCatalog`:
+Alternatively, as of 6.2, there is a `@Fallback` annotation for demarcating
+any beans other than the regular ones to be injected. If only one regular
+bean is left, it is effectively primary as well:
+
+[tabs]
+======
+Java::
++
+[source,java,indent=0,subs="verbatim,quotes",role="primary"]
+----
+	@Configuration
+	public class MovieConfiguration {
+
+		@Bean
+		public MovieCatalog firstMovieCatalog() { ... }
+
+		@Bean
+		@Fallback
+		public MovieCatalog secondMovieCatalog() { ... }
+
+		// ...
+	}
+----
+
+Kotlin::
++
+[source,kotlin,indent=0,subs="verbatim,quotes",role="secondary"]
+----
+	@Configuration
+	class MovieConfiguration {
+
+		@Bean
+		fun firstMovieCatalog(): MovieCatalog { ... }
+
+		@Bean
+		@Fallback
+		fun secondMovieCatalog(): MovieCatalog { ... }
+
+		// ...
+	}
+----
+======
+
+With both variants of the preceding configuration, the following
+`MovieRecommender` is autowired with the `firstMovieCatalog`:
 
 [tabs]
 ======

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

@@ -1,12 +1,13 @@
 [[beans-autowired-annotation-qualifiers]]
 = Fine-tuning Annotation-based Autowiring with Qualifiers
 
-`@Primary` is an effective way to use autowiring by type with several instances when one
-primary candidate can be determined. When you need more control over the selection process,
-you can use Spring's `@Qualifier` annotation. You can associate qualifier values
-with specific arguments, narrowing the set of type matches so that a specific bean is
-chosen for each argument. In the simplest case, this can be a plain descriptive value, as
-shown in the following example:
+`@Primary` and `@Fallback` are effective ways to use autowiring by type with several
+instances when one primary (or non-fallback) candidate can be determined.
+
+When you need more control over the selection process, you can use Spring's `@Qualifier`
+annotation. You can associate qualifier values with specific arguments, narrowing the set
+of type matches so that a specific bean is chosen for each argument. In the simplest case,
+this can be a plain descriptive value, as shown in the following example:
 
 --
 [tabs]