/*
* Copyright 2002-2016 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.springframework.scheduling.annotation;
import java.lang.annotation.Annotation;
import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
import org.springframework.context.annotation.AdviceMode;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Import;
import org.springframework.core.Ordered;
/**
* Enables Spring's asynchronous method execution capability, similar to functionality
* found in Spring's {@code <task:*>} XML namespace.
*
* <p>To be used together with @{@link Configuration Configuration} classes as follows,
* enabling annotation-driven async processing for an entire Spring application context:
*
* <pre class="code">
* @Configuration
* @EnableAsync
* public class AppConfig {
*
* }</pre>
*
* {@code MyAsyncBean} is a user-defined type with one or more methods annotated with
* either Spring's {@code @Async} annotation, the EJB 3.1 {@code @javax.ejb.Asynchronous}
* annotation, or any custom annotation specified via the {@link #annotation} attribute.
* The aspect is added transparently for any registered bean, for instance via this
* configuration:
*
* <pre class="code">
* @Configuration
* public class AnotherAppConfig {
*
* @Bean
* public MyAsyncBean asyncBean() {
* return new MyAsyncBean();
* }
* }</pre>
*
* <p>The {@link #mode} attribute controls how advice is applied; if the mode is
* {@link AdviceMode#PROXY} (the default), then the other attributes control the behavior
* of the proxying.
*
* <p>Note that if the {@linkplain #mode} is set to {@link AdviceMode#ASPECTJ}, then the
* value of the {@link #proxyTargetClass} attribute will be ignored. Note also that in
* this case the {@code spring-aspects} module JAR must be present on the classpath.
*
* <p>By default, Spring will be searching for an associated thread pool definition:
* either a unique {@link org.springframework.core.task.TaskExecutor} bean in the context,
* or an {@link java.util.concurrent.Executor} bean named "taskExecutor" otherwise. If
* neither of the two is resolvable, a {@link org.springframework.core.task.SimpleAsyncTaskExecutor}
* will be used to process async method invocations. Besides, annotated methods having a
* {@code void} return type cannot transmit any exception back to the caller. By default,
* such uncaught exceptions are only logged.
*
* <p>To customize all this, implement {@link AsyncConfigurer} and provide:
* <ul>
* <li>your own {@link java.util.concurrent.Executor Executor} through the
* {@link AsyncConfigurer#getAsyncExecutor getAsyncExecutor()} method, and</li>
* <li>your own {@link org.springframework.aop.interceptor.AsyncUncaughtExceptionHandler
* AsyncUncaughtExceptionHandler} through the {@link AsyncConfigurer#getAsyncUncaughtExceptionHandler
* getAsyncUncaughtExceptionHandler()}
* method.</li>
* </ul>
*
* <pre class="code">
* @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();
* }
* }</pre>
*
* <p>If only one item needs to be customized, {@code null} can be returned to
* keep the default settings. Consider also extending from {@link AsyncConfigurerSupport}
* when possible.
*
* <p>Note: In the above example the {@code ThreadPoolTaskExecutor} is not a fully managed
* Spring bean. Add the {@code @Bean} annotation to the {@code getAsyncExecutor()} method
* if you want a fully managed bean. In such circumstances it is no longer necessary to
* manually call the {@code executor.initialize()} method as this will be invoked
* automatically when the bean is initialized.
*
* <p>For reference, the example above can be compared to the following Spring XML
* configuration:
*
* <pre class="code">
* {@code
* <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>
* }</pre>
*
* The above XML-based and JavaConfig-based examples are equivalent except for the
* setting of the <em>thread name prefix</em> of the {@code Executor}; this is because
* the {@code <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.
*
* @author Chris Beams
* @author Juergen Hoeller
* @author Stephane Nicoll
* @author Sam Brannen
* @since 3.1
* @see Async
* @see AsyncConfigurer
* @see AsyncConfigurationSelector
*/
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Import(AsyncConfigurationSelector.class)
public @interface EnableAsync {
/**
* Indicate the 'async' annotation type to be detected at either class
* or method level.
* <p>By default, both Spring's @{@link Async} annotation and the EJB 3.1
* {@code @javax.ejb.Asynchronous} annotation will be detected.
* <p>This attribute exists so that developers can provide their own
* custom annotation type to indicate that a method (or all methods of
* a given class) should be invoked asynchronously.
*/
Class<? extends Annotation> annotation() default Annotation.class;
/**
* Indicate whether subclass-based (CGLIB) proxies are to be created as opposed
* to standard Java interface-based proxies.
* <p><strong>Applicable only if the {@link #mode} is set to {@link AdviceMode#PROXY}</strong>.
* <p>The default is {@code false}.
* <p>Note that setting this attribute to {@code true} will affect <em>all</em>
* Spring-managed beans requiring proxying, not just those marked with {@code @Async}.
* For example, other beans marked with Spring's {@code @Transactional} annotation
* will be upgraded to subclass proxying at the same time. This approach has no
* negative impact in practice unless one is explicitly expecting one type of proxy
* vs. another — for example, in tests.
*/
boolean proxyTargetClass() default false;
/**
* Indicate how async advice should be applied.
* <p>The default is {@link AdviceMode#PROXY}.
* @see AdviceMode
*/
AdviceMode mode() default AdviceMode.PROXY;
/**
* Indicate the order in which the {@link AsyncAnnotationBeanPostProcessor}
* should be applied.
* <p>The default is {@link Ordered#LOWEST_PRECEDENCE} in order to run
* after all other post-processors, so that it can add an advisor to
* existing proxies rather than double-proxy.
*/
int order() default Ordered.LOWEST_PRECEDENCE;
}