Enables Spring's asynchronous method execution capability, similar to functionality
found in Spring's
<task:*>
XML namespace.
To be used together with @Configuration
classes as follows,
enabling annotation-driven async processing for an entire Spring application context:
@Configuration
@EnableAsync
public class AppConfig {
}
MyAsyncBean
is a user-defined type with one or more methods annotated with
either Spring's
@Async
annotation, the EJB 3.1
@javax.ejb.Asynchronous
annotation, or any custom annotation specified via the
annotation()
attribute.
The aspect is added transparently for any registered bean, for instance via this
configuration:
@Configuration
public class AnotherAppConfig {
@Bean
public MyAsyncBean asyncBean() {
return new MyAsyncBean();
}
}
By default, Spring will be searching for an associated thread pool definition:
either a unique TaskExecutor
bean in the context,
or an Executor
bean named "taskExecutor" otherwise. If
neither of the two is resolvable, a SimpleAsyncTaskExecutor
will be used to process async method invocations. Besides, annotated methods having a
void
return type cannot transmit any exception back to the caller. By default,
such uncaught exceptions are only logged.
To customize all this, implement AsyncConfigurer
and provide:
NOTE: AsyncConfigurer
configuration classes get initialized early
in the application context bootstrap. If you need any dependencies on other beans
there, make sure to declare them 'lazy' as far as possible in order to let them
go through other post-processors as well.
@Configuration
@EnableAsync
public class AppConfig implements AsyncConfigurer {
@Override
public Executor getAsyncExecutor() {
ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();
executor.setCorePoolSize(7);
executor.setMaxPoolSize(42);
executor.setQueueCapacity(11);
executor.setThreadNamePrefix("MyExecutor-");
executor.initialize();
return executor;
}
@Override
public AsyncUncaughtExceptionHandler getAsyncUncaughtExceptionHandler() {
return MyAsyncUncaughtExceptionHandler();
}
}
If only one item needs to be customized, null
can be returned to
keep the default settings. Consider also extending from AsyncConfigurerSupport
when possible.
Note: In the above example the ThreadPoolTaskExecutor
is not a fully managed
Spring bean. Add the @Bean
annotation to the getAsyncExecutor()
method
if you want a fully managed bean. In such circumstances it is no longer necessary to
manually call the executor.initialize()
method as this will be invoked
automatically when the bean is initialized.
For reference, the example above can be compared to the following Spring XML
configuration:
<beans>
<task:annotation-driven executor="myExecutor" exception-handler="exceptionHandler"/>
<task:executor id="myExecutor" pool-size="7-42" queue-capacity="11"/>
<bean id="asyncBean" class="com.foo.MyAsyncBean"/>
<bean id="exceptionHandler" class="com.foo.MyAsyncUncaughtExceptionHandler"/>
</beans>
The above XML-based and JavaConfig-based examples are equivalent except for the
setting of the
thread name prefix of the
Executor
; this is because
the
<task:executor>
element does not expose such an attribute. This
demonstrates how the JavaConfig-based approach allows for maximum configurability
through direct access to actual componentry.
The mode()
attribute controls how advice is applied: If the mode is
AdviceMode.PROXY
(the default), then the other attributes control the behavior
of the proxying. Please note that proxy mode allows for interception of calls through
the proxy only; local calls within the same class cannot get intercepted that way.
Note that if the mode() is set to AdviceMode.ASPECTJ
, then the
value of the proxyTargetClass()
attribute will be ignored. Note also that in
this case the spring-aspects
module JAR must be present on the classpath, with
compile-time weaving or load-time weaving applying the aspect to the affected classes.
There is no proxy involved in such a scenario; local calls will be intercepted as well.