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
In anticipation of substantive changes required to implement @Async
executor qualification, the following updates have been made to the
components and infrastructure supporting @Async functionality:
- Fix trailing whitespace and indentation errors
- Fix generics warnings
- Add Javadoc where missing, update to use {@code} tags, etc.
- Avoid NPE in AopUtils#canApply
- Organize imports to follow conventions
- Remove System.out.println statements from tests
- Correct various punctuation and grammar problems
Before this change there were numerous javadoc warnings being reported
while building Spring framework API.
This commit resolves most of the javadoc warnings, reducing the total
number from 265 to 103.
Issue: SPR-9113
This renaming more intuitively expresses the relationship between
subprojects and the JAR artifacts they produce.
Tracking history across these renames is possible, but it requires
use of the --follow flag to `git log`, for example
$ git log spring-aop/src/main/java/org/springframework/aop/Advisor.java
will show history up until the renaming event, where
$ git log --follow spring-aop/src/main/java/org/springframework/aop/Advisor.java
will show history for all changes to the file, before and after the
renaming.
See http://chrisbeams.com/git-diff-across-renamed-directories
Chris Beams
Stevo Slavic