@EnableAsync
@Target(ElementType.TYPE) @Retention(RetentionPolicy.RUNTIME) @Documented @Import(AsyncConfigurationSelector.class) public @interface EnableAsync { Class<? extends Annotation> annotation() default Annotation.class; boolean proxyTargetClass() default false; AdviceMode mode() default AdviceMode.PROXY; int order() default Ordered.LOWEST_PRECEDENCE; }
@EnableAsync注解即开启Spring对方法异步执行的能力,需要和注解@Configuration配合使用。
@Configuration @EnableAsync public class AppConfig { }
也可以自定义线程池
@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(); } }
@Async
@Target({ElementType.METHOD, ElementType.TYPE}) @Retention(RetentionPolicy.RUNTIME) @Documented public @interface Async { String value() default ""; }
在要异步执行的方法上使用@Async注解,下面是一个没有返回值,一个带有返回值的异步调用的示例。
@Component public class AsyncTask { @Async public void task1() { try { Thread.sleep(3000); } catch (InterruptedException e) { e.printStackTrace(); } } @Async public Future<String> task2() { try { Thread.sleep(3000); } catch (InterruptedException e) { e.printStackTrace(); } return new AsyncResult<String>("javastack"); }
}
测试代码
@RunWith(SpringRunner.class) @SpringBootTest public class AsyncTest { private final static Logger log = LoggerFactory.getLogger(AsyncTest.class); @Autowired private AsyncTask asyncTask; @Test public void testTask1(){ log.info("start"); asyncTask.task1(); log.info("finish"); } @Test public void testTask2() { log.info("start"); Future<String> future = asyncTask.task2(); while (true) { if (future.isDone()) { try { log.info("result is " + future.get()); } catch (Exception e) { e.printStackTrace(); } break; } } log.info("finish"); } }
注意事项
1、使用注意
@Async只能使用到被代理的对象方法上,即代理类的入口方法处,且方法必须是public的。
2、事务处理机制
使用@Async异步注解不能和@Transaction事务注解在同一个方法上同时使用,不然事务注解将无效。
要使用事务,需要把事务注解提取到方法里面的子方法上。