SpringBoot实践之---异步调用Async

我会带着你远行 2023-10-23 00:44 156阅读 0赞

什么是异步调用？

异步调用是相对于同步调用而言的，同步调用是指程序按预定顺序一步步执行，每一步必须等到上一步执行完后才能执行，异步调用则无需等待上一步程序执行完即可执行。

启动类：添加@EnableAsync注解

@SpringBootApplication
    @EnableAsync
    public class Application{
     
        public static void main(String[] args) {
            SpringApplication.run(Application.class, args);
        }
    }

**Controller**

只需在需要异步执行方法上添加@Async注解

@RestController
    @RequestMapping("")
    public class AsyncTaskController {
    	
    	@RequestMapping("")
    	public String doTask() throws InterruptedException{
    		long currentTimeMillis = System.currentTimeMillis();
    		this.task1();
    		this.task2();
    		this.task3();
    		long currentTimeMillis1 = System.currentTimeMillis();
    		return "task任务总耗时:"+(currentTimeMillis1-currentTimeMillis)+"ms";
    	}
    	
    	@Async
    	public void task1() throws InterruptedException{
    		long currentTimeMillis = System.currentTimeMillis();
    		Thread.sleep(1000);
    		long currentTimeMillis1 = System.currentTimeMillis();
    		System.out.println("task1任务耗时:"+(currentTimeMillis1-currentTimeMillis)+"ms");
    	}
    	
    	@Async
    	public void task2() throws InterruptedException{
    		long currentTimeMillis = System.currentTimeMillis();
    		Thread.sleep(2000);
    		long currentTimeMillis1 = System.currentTimeMillis();
    		System.out.println("task2任务耗时:"+(currentTimeMillis1-currentTimeMillis)+"ms");
    	}
    	@Async
    	public void task3() throws InterruptedException{
    		long currentTimeMillis = System.currentTimeMillis();
    		Thread.sleep(3000);
    		long currentTimeMillis1 = System.currentTimeMillis();
    		System.out.println("task3任务耗时:"+(currentTimeMillis1-currentTimeMillis)+"ms");
    	}
    }

**异步并没有执行！**

难道是代码写错了？反复检查了好几遍，并没有发现什么明显错误，想起spring对@Transactional注解时也有类似问题，spring扫描时具有@Transactional注解方法的类时，**是生成一个代理类，由代理类去开启关闭事务，而在同一个类中，方法调用是在类体内执行的，spring无法截获这个方法调用。**

Controller

异步任务类

@Component
    public class AsyncTask {
    	
    	@Async
    	public void task1() throws InterruptedException{
    		long currentTimeMillis = System.currentTimeMillis();
    		Thread.sleep(1000);
    		long currentTimeMillis1 = System.currentTimeMillis();
    		System.out.println("task1任务耗时:"+(currentTimeMillis1-currentTimeMillis)+"ms");
    	}
    	
    	@Async
    	public void task2() throws InterruptedException{
    		long currentTimeMillis = System.currentTimeMillis();
    		Thread.sleep(2000);
    		long currentTimeMillis1 = System.currentTimeMillis();
    		System.out.println("task2任务耗时:"+(currentTimeMillis1-currentTimeMillis)+"ms");
    	}
    	@Async
    	public void task3() throws InterruptedException{
    		long currentTimeMillis = System.currentTimeMillis();
    		Thread.sleep(3000);
    		long currentTimeMillis1 = System.currentTimeMillis();
    		System.out.println("task3任务耗时:"+(currentTimeMillis1-currentTimeMillis)+"ms");
    	}
    }

异步调用成功

如何知道三个异步任务什么时候执行完，执行的结果怎样呢？可以采用添加Fature回调方式判断

代码入下：

**异步任务类**

@Component
    public class AsyncTask {
    	
    	@Async
    	public Future<String> task1() throws InterruptedException{
    		long currentTimeMillis = System.currentTimeMillis();
    		Thread.sleep(1000);
    		long currentTimeMillis1 = System.currentTimeMillis();
    		System.out.println("task1任务耗时:"+(currentTimeMillis1-currentTimeMillis)+"ms");
    		return new AsyncResult<String>("task1执行完毕");
    	}
    	
    	@Async
    	public Future<String> task2() throws InterruptedException{
    		long currentTimeMillis = System.currentTimeMillis();
    		Thread.sleep(2000);
    		long currentTimeMillis1 = System.currentTimeMillis();
    		System.out.println("task2任务耗时:"+(currentTimeMillis1-currentTimeMillis)+"ms");
    		return new AsyncResult<String>("task2执行完毕");
    	}
    	@Async
    	public Future<String> task3() throws InterruptedException{
    		long currentTimeMillis = System.currentTimeMillis();
    		Thread.sleep(3000);
    		long currentTimeMillis1 = System.currentTimeMillis();
    		System.out.println("task3任务耗时:"+(currentTimeMillis1-currentTimeMillis)+"ms");
    		return new AsyncResult<String>("task3执行完毕");
    	}
    }

@RequestMapping("")
    @RestController
    public class AsyncTaskController {
    	
    	@Autowired
    	private AsyncTask asyncTask;
    	
    	@RequestMapping("")
    	public String doTask() throws InterruptedException{
    		long currentTimeMillis = System.currentTimeMillis();
    		Future<String> task1 = asyncTask.task1();
    		Future<String> task2 = asyncTask.task2();
    		Future<String> task3 = asyncTask.task3();
    		String result = null;
    		for (;;) {
    			if(task1.isDone() && task2.isDone() && task3.isDone()) {
    				// 三个任务都调用完成，退出循环等待
    				break;
    			}
    			Thread.sleep(1000);
    		}
    		long currentTimeMillis1 = System.currentTimeMillis();
    		result = "task任务总耗时:"+(currentTimeMillis1-currentTimeMillis)+"ms";
    		return result;
    	}
    }

异步调用成功，并且在所有任务都完成时程序才返回了结果！

[原文][Link 1]

[Link 1]: https://blog.csdn.net/luckykapok918/article/details/79105929