Documentation notes for @Bean overriding and bean name matching
See gh-31052 See gh-28122
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@ -154,17 +154,19 @@ Letting qualifier values select against target bean names, within the type-match
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candidates, does not require a `@Qualifier` annotation at the injection point.
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If there is no other resolution indicator (such as a qualifier or a primary marker),
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for a non-unique dependency situation, Spring matches the injection point name
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(that is, the field name or parameter name) against the target bean names and chooses the
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same-named candidate, if any.
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(that is, the field name or parameter name) against the target bean names and chooses
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the same-named candidate, if any (either by bean name or by associated alias).
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Since version 6.1, this requires the `-parameters` Java compiler flag to be present.
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As of 6.2, the container applies fast shortcut resolution for bean name matches,
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bypassing the full type matching algorithm when the parameter name matches the
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bean name and no type, qualifier or primary conditions override the match. It is
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therefore recommendable for your parameter names to match the target bean names.
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====
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That said, if you intend to express annotation-driven injection by name, do not
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primarily use `@Autowired`, even if it is capable of selecting by bean name among
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type-matching candidates. Instead, use the JSR-250 `@Resource` annotation, which is
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semantically defined to identify a specific target component by its unique name, with
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the declared type being irrelevant for the matching process. `@Autowired` has rather
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As an alternative for injection by name, consider the JSR-250 `@Resource` annotation
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which is semantically defined to identify a specific target component by its unique name,
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with the declared type being irrelevant for the matching process. `@Autowired` has rather
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different semantics: After selecting candidate beans by type, the specified `String`
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qualifier value is considered within those type-selected candidates only (for example,
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matching an `account` qualifier against beans marked with the same qualifier label).
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@ -73,6 +73,8 @@ runtime (concurrently with live access to the factory) is not officially support
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lead to concurrent access exceptions, inconsistent state in the bean container, or both.
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====
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[[beans-definition-overriding]]
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== Overriding Beans
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@ -81,15 +83,26 @@ already allocated. While bean overriding is possible, it makes the configuration
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to read and this feature will be deprecated in a future release.
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To disable bean overriding altogether, you can set the `allowBeanDefinitionOverriding`
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to `false` on the `ApplicationContext` before it is refreshed. In such setup, an
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flag to `false` on the `ApplicationContext` before it is refreshed. In such setup, an
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exception is thrown if bean overriding is used.
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By default, the container logs every bean overriding at `INFO` level so that you can
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adapt your configuration accordingly. While not recommended, you can silence those logs
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by setting the `allowBeanDefinitionOverriding` flag to `true`.
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NOTE: We acknowledge that overriding beans in a test is convenient, and there is
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explicit support for this. For more details please refer to xref:testing/testcontext-framework/bean-overriding.adoc[this section].
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.Java-configuration
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****
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If you use Java Configuration, a corresponding `@Bean` method always silently overrides
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a scanned bean class with the same component name as long as the return type of the
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`@Bean` method matches that bean class. This simply means that the container will call
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the `@Bean` factory method in favor of any pre-declared constructor on the bean class.
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****
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NOTE: We acknowledge that overriding beans in a test scenario is convenient,
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and there is explicit support for this as of Spring Framework 6.2. Please refer to
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xref:testing/testcontext-framework/bean-overriding.adoc[this section] for more details.
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[[beans-beanname]]
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== Naming Beans
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