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由 Chris Beams 提交于
Prior to this change, Spring's @Async annotation support was tied to a single AsyncTaskExecutor bean, meaning that all methods marked with @Async were forced to use the same executor. This is an undesirable limitation, given that certain methods may have different priorities, etc. This leads to the need to (optionally) qualify which executor should handle each method. This is similar to the way that Spring's @Transactional annotation was originally tied to a single PlatformTransactionManager, but in Spring 3.0 was enhanced to allow for a qualifier via the #value attribute, e.g. @Transactional("ptm1") public void m() { ... } where "ptm1" is either the name of a PlatformTransactionManager bean or a qualifier value associated with a PlatformTransactionManager bean, e.g. via the <qualifier> element in XML or the @Qualifier annotation. This commit introduces the same approach to @Async and its relationship to underlying executor beans. As always, the following syntax remains supported @Async public void m() { ... } indicating that calls to #m will be delegated to the "default" executor, i.e. the executor provided to <task:annotation-driven executor="..."/> or the executor specified when authoring a @Configuration class that implements AsyncConfigurer and its #getAsyncExecutor method. However, it now also possible to qualify which executor should be used on a method-by-method basis, e.g. @Async("e1") public void m() { ... } indicating that calls to #m will be delegated to the executor bean named or otherwise qualified as "e1". Unlike the default executor which is specified up front at configuration time as described above, the "e1" executor bean is looked up within the container on the first execution of #m and then cached in association with that method for the lifetime of the container. Class-level use of Async#value behaves as expected, indicating that all methods within the annotated class should be executed with the named executor. In the case of both method- and class-level annotations, any method-level #value overrides any class level #value. This commit introduces the following major changes: - Add @Async#value attribute for executor qualification - Introduce AsyncExecutionAspectSupport as a common base class for both MethodInterceptor- and AspectJ-based async aspects. This base class provides common structure for specifying the default executor (#setExecutor) as well as logic for determining (and caching) which executor should execute a given method (#determineAsyncExecutor) and an abstract method to allow subclasses to provide specific strategies for executor qualification (#getExecutorQualifier). - Introduce AnnotationAsyncExecutionInterceptor as a specialization of the existing AsyncExecutionInterceptor to allow for introspection of the @Async annotation and its #value attribute for a given method. Note that this new subclass was necessary for packaging reasons - the original AsyncExecutionInterceptor lives in org.springframework.aop and therefore does not have visibility to the @Async annotation in org.springframework.scheduling.annotation. This new subclass replaces usage of AsyncExecutionInterceptor throughout the framework, though the latter remains usable and undeprecated for compatibility with any existing third-party extensions. - Add documentation to spring-task-3.2.xsd and reference manual explaining @Async executor qualification - Add tests covering all new functionality Note that the public API of all affected components remains backward- compatible. Issue: SPR-6847
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