1、任务执行和调度
Spring用TaskExecutor和TaskScheduler接口提供了异步执行和调度任务的抽象。
Spring的TaskExecutor和java.util.concurrent.Executor接口时一样的，这个接口只有一个方法execute(Runnable task)。
1.1、TaskExecutor类型
Spring已经内置了许多TaskExecutor的实现，你没有必要自己去实现：
- SimpleAsyncTaskExecutor这种实现不会重用任何线程，每次调用都会创建一个新的线程。
- SyncTaskExecutor这种实现不会异步的执行
- ConcurrentTaskExecutor这种实现是java.util.concurrent.Executor的一个adapter。
- SimpleThreadPoolTaskExecutor这种实现实际上是Quartz的SimpleThreadPool的一个子类，它监听Spring的声明周期回调。
- ThreadPoolTaskExecutor这是最常用最通用的一种实现。它包含了java.util.concurrent.ThreadPoolExecutor的属性，并且用TaskExecutor进行包装。
1.2、注解支持调度和异步执行
To enable support for @Scheduled and @Async annotations add @EnableScheduling and @EnableAsync to one of your @Configuration classes:
@Configuration @EnableAsync @EnableScheduling public class AppConfig { } 特别注意
The default advice mode for processing
@Asyncannotations is "proxy" which allows for interception of calls through the proxy only; local calls within the same class cannot get intercepted that way. For a more advanced mode of interception, consider switching to "aspectj" mode in combination with compile-time or load-time weaving.
默认是用代理去处理@Async的，因此，相同类中的方法调用带@Async的方法是无法异步的，这种情况仍然是同步。
举个例子：下面这种，在外部直接调用sayHi()是可以异步执行的，而调用sayHello()时sayHi()仍然是同步执行
public class A { public void sayHello() { sayHi(); } @Async public void sayHi() { } } 1.3、@Async注解
在方法上加@Async注解表示这是一个异步调用。换句话说，方法的调用者会立即得到返回，并且实际的方法执行是想Spring的TaskExecutor提交了一个任务。
In other words, the caller will return immediately upon invocation and the actual execution of the method will occur in a task that has been submitted to a Spring TaskExecutor.
@Async void doSomething() { // this will be executed asynchronously } @Async void doSomething(String s) { // this will be executed asynchronously } @Async Future<String> returnSomething(int i) { // this will be executed asynchronously } 注意：
@Async methods may not only declare a regular java.util.concurrent.Future return type but also Spring’s org.springframework.util.concurrent.ListenableFuture or, as of Spring 4.2, JDK 8’s java.util.concurrent.CompletableFuture: for richer interaction with the asynchronous task and for immediate composition with further processing steps.
1.4、@Async限定Executor
默认情况下，当在方法上加@Async注解时，将会使用一个支持注解驱动的Executor。然而，@Async注解的value值可以指定一个别的Executor
@Async("otherExecutor") void doSomething(String s) { // this will be executed asynchronously by "otherExecutor" } 这里，otherExecutor是Spring容器中任意Executor bean的名字。
1.5、@Async异常管理
当一个@Async方法有一个Future类型的返回值时，就很容易管理在调Future的get()方法获取任务的执行结果时抛出的异常。如果返回类型是void，那么异常是不会被捕获到的。
public class MyAsyncUncaughtExceptionHandler implements AsyncUncaughtExceptionHandler { @Override public void handleUncaughtException(Throwable ex, Method method, Object... params) { // handle exception } } 1 3 import org.springframework.context.annotation.Bean; 4 import org.springframework.context.annotation.Configuration; 5 import org.springframework.scheduling.annotation.EnableAsync; 6 import org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor; 7 8 @Configuration 9 @EnableAsync 10 public class TaskExecutorConfig { 11 12 private Integer corePoolSize = 30; 13 14 private Integer maxPoolSize = 50; 15 16 private Integer keepAliveSeconds = 300; 17 18 // private Integer queueCapacity = 2000; 19 20 @Bean("myThreadPoolTaskExecutor") 21 public ThreadPoolTaskExecutor myThreadPoolTaskExecutor() { 22 ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor(); 23 executor.setCorePoolSize(corePoolSize); 24 executor.setMaxPoolSize(maxPoolSize); 25 executor.setKeepAliveSeconds(keepAliveSeconds); 26 // executor.setQueueCapacity(queueCapacity); 27 executor.setWaitForTasksToCompleteOnShutdown(true); 28 executor.initialize(); 29 return executor; 30 } 31 32 } 调用
1 @Async("myThreadPoolTaskExecutor") 2 @Override 3 public void present(CouponPresentLogEntity entity) { 4 try { 5 CouponBaseResponse rst = couponSendRpcService.send(entity.getUserId(), entity.getCouponBatchKey(), "1", entity.getVendorId()); 6 if (null != rst && rst.isSuccess()) { 7 entity.setStatus(PresentStatusEnum.SUCCESS.getType()); 8 }else { 9 String reason = (null == rst) ? "响应异常" : rst.getMsg(); 10 entity.setFailureReason(reason); 11 entity.setStatus(PresentStatusEnum.FAILURE.getType()); 12 } 13 }catch (Exception ex) { 14 log.error(ex.getMessage(), ex); 15 entity.setFailureReason(ex.getMessage()); 16 entity.setStatus(PresentStatusEnum.FAILURE.getType()); 17 } 18 couponPresentLogDao.update(entity); 19 } 结果
[INFO ] 2018-05-09 16:27:39.887 [myThreadPoolTaskExecutor-1] [com.ourhours.coupon.rpc.dubbo.ReceiveLogFilter] - receive method-name:send; arguments:[10046031,"4d7cc32f8f7e4b00bca56f6bf4b3b658","1",10001] [INFO ] 2018-05-09 16:27:39.889 [myThreadPoolTaskExecutor-2] [com.ourhours.coupon.rpc.dubbo.ReceiveLogFilter] - receive method-name:send; arguments:[10046031,"4d7cc32f8f7e4b00bca56f6bf4b3b658","1",10001]
Spring Framework Reference Documentation 4.3.17.RELEASE
