Consolidate self injection documentation in the reference manual

Closes gh-33454
This commit is contained in:
Sam Brannen
2024-08-30 15:47:54 +02:00
parent a19acc65b4
commit 5e1de19ba3
2 changed files with 32 additions and 26 deletions

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@@ -179,27 +179,10 @@ is preserved in `@Bean` return type signatures or collection inheritance hierarc
In this case, you can use qualifier values to select among same-typed collections,
as outlined in the previous paragraph.
`@Autowired` also considers self references for injection (that is, references
back to the bean that is currently injected). Note that self injection is a fallback.
Regular dependencies on other components always have precedence. In that sense, self
references do not participate in regular candidate selection and are therefore in
particular never primary. On the contrary, they always end up as lowest precedence.
In practice, you should use self references as a last resort only (for example, for
calling other methods on the same instance through the bean's transactional proxy).
Consider factoring out the affected methods to a separate delegate bean in such a scenario.
Alternatively, you can use `@Resource`, which may obtain a proxy back to the current bean
by its unique name.
[NOTE]
====
Trying to inject the results from `@Bean` methods on the same configuration class is
effectively a self-reference scenario as well. Either lazily resolve such references
in the method signature where it is actually needed (as opposed to an autowired field
in the configuration class) or declare the affected `@Bean` methods as `static`,
decoupling them from the containing configuration class instance and its lifecycle.
Otherwise, such beans are only considered in the fallback phase, with matching beans
on other configuration classes selected as primary candidates instead (if available).
====
`@Autowired` also considers self references for injection (that is, references back to
the bean that is currently injected). See
xref:core/beans/annotation-config/autowired.adoc#beans-autowired-annotation-self-injection[Self Injection]
for details.
`@Autowired` applies to fields, constructors, and multi-argument methods, allowing for
narrowing through qualifier annotations at the parameter level. In contrast, `@Resource`

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@@ -186,14 +186,37 @@ implementation type, consider declaring the most specific return type on your fa
method (at least as specific as required by the injection points referring to your bean).
====
.[[beans-autowired-annotation-self-injection]]Self Injection
****
`@Autowired` also considers self references for injection (that is, references back to
the bean that is currently injected).
Note, however, that self injection is a fallback mechanism. Regular dependencies on other
components always have precedence. In that sense, self references do not participate in
regular autowiring candidate selection and are therefore in particular never primary. On
the contrary, they always end up as lowest precedence.
In practice, you should use self references as a last resort only for example, for
calling other methods on the same instance through the bean's transactional proxy. As an
alternative, consider factoring out the affected methods to a separate delegate bean in
such a scenario.
Another alternative is to use `@Resource`, which may obtain a proxy back to the current
bean by its unique name.
======
[NOTE]
====
As of 4.3, `@Autowired` also considers self references for injection (that is, references
back to the bean that is currently injected). Note that self injection is a fallback.
In practice, you should use self references as a last resort only (for example, for
calling other methods on the same instance through the bean's transactional proxy).
Consider factoring out the affected methods to a separate delegate bean in such a scenario.
Trying to inject the results from `@Bean` methods in the same `@Configuration` class is
effectively a self-reference scenario as well. Either lazily resolve such references
in the method signature where it is actually needed (as opposed to an autowired field
in the configuration class) or declare the affected `@Bean` methods as `static`,
decoupling them from the containing configuration class instance and its lifecycle.
Otherwise, such beans are only considered in the fallback phase, with matching beans
on other configuration classes selected as primary candidates instead (if available).
====
======
****
You can also instruct Spring to provide all beans of a particular type from the
`ApplicationContext` by adding the `@Autowired` annotation to a field or method that