SpringBoot整合异步执行程序及使用场景

使用场景：

1.  发送短信
2. 发送邮件
3. App消息推送
4. 节省运维凌晨发布任务时间提高效率 等

 使用异步执行的优点：

异步比同步快很多，节省更多的时间，提高效率

步骤

 1，使用注解@EnableAsync开启异步，会自动扫描

@SpringBootApplication
@EnableAsync
public class SchedulingApplication {

    public static void main(String[] args) {
        SpringApplication.run(SchedulingApplication.class, args);
    }
}

2，定义@Component @Async 作为组件被容器扫描执行

返回的Future接口，用于后续判断任务是否已执行完毕

@Component
public class AsyncTask {

    @Async
    public Future doTask1() throws Exception{
        long start = System.currentTimeMillis();
        Thread.sleep(1000);
        long end = System.currentTimeMillis();
        System.out.println("任务一耗时："+ (end-start)+"毫秒");
        return new AsyncResult<>(true);
    }

    @Async
    public Future doTask2() throws Exception{
        long start = System.currentTimeMillis();
        Thread.sleep(700);
        long end = System.currentTimeMillis();
        System.out.println("任务二耗时："+ (end-start)+"毫秒");
        return new AsyncResult<>(true);
    }

    @Async
    public Future doTask3() throws Exception{
        long start = System.currentTimeMillis();
        Thread.sleep(600);
        long end = System.currentTimeMillis();
        System.out.println("任务三耗时："+ (end-start)+"毫秒");
        return new AsyncResult<>(true);
    }

}

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Controller层执行，

@RestController
@RequestMapping("tasks")
public class DoTask {

    @Autowired
    private AsyncTask asyncTask;

    @RequestMapping("test")
    public String test() throws Exception {
        long start = System.currentTimeMillis();

        Future a = asyncTask.doTask1(); //异步执行
        Future b = asyncTask.doTask2(); //异步执行
        Future c = asyncTask.doTask3(); //异步执行

        while(!a.isDone()||!b.isDone()||!c.isDone()){
            if(a.isDone()&&b.isDone()&&c.isDone()){
                break;
            }
        }

        long end = System.currentTimeMillis();
        String times = "任务全部完成，总耗时："+(end-start)+"毫秒";
        System.out.println(times);

        return times;
    }
}

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Future接口简单介绍

 

Future 接口                                                                                                        

接口函数及含义 ：public interface Future

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 boolean  cancel(boolean mayInterruptIfRunning)

取消当前执行的任务，如果已经执行完毕或者已经被取消/由于某种原因不能被取消 则取消任务失败。

参数mayInterruptIfRunning： 当任务正在执行，如果参数为true ，则尝试中断任务，否则让任务继续执行知道结束。

---

boolean isCancelled()

Returns {@code true} if this task was cancelled before it completed
* normally.

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boolean isDone();

/**
 * Returns {@code true} if this task completed.
 *
 * Completion may be due to normal termination, an exception, or
 * cancellation -- in all of these cases, this method will return
 * {@code true}.
 *
 * @return {@code true} if this task completed
 */

---

V get() throws InterruptedException, ExecutionException;

/**
 * Waits if necessary for the computation to complete, and then
 * retrieves its result.
 *
 * @return the computed result
 * @throws CancellationException if the computation was cancelled
 * @throws ExecutionException if the computation threw an
 * exception
 * @throws InterruptedException if the current thread was interrupted
 * while waiting
 */

由注释可以看出，当没有执行完成时，需要等待任务执行完成了才会将计算结果返回。

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V get(long timeout, TimeUnit unit)
throws InterruptedException, ExecutionException, TimeoutException;

Waits if necessary for at most the given time for the computation
* to complete, and then retrieves its result, if available.

如果等待的时间超过设置的时间则会报 TimeoutException异常。

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参考来源：

http://www.cnblogs.com/NeilZhang/p/8870062.html

https://www.imooc.com/video/16793