springBoot异步执行方法@Async

深藏阁楼爱情的钟 2021-12-18 21:07 358阅读 0赞

我们在使用多线程的时候，往往需要创建Thread类，或者实现Runnable接口，如果要使用到线程池，我们还需要创建Exectors。而在Spring中只要@EnableAsync就可以开启多线程，使用@Async就可以定义一个线程任务。

1、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。

2、如何实现异步调用

多线程，这是很多人第一眼想到的关键词，没错，多线程就是一种实现异步调用的方式。  
    在非spring目项目中我们要实现异步调用的就是使用多线程方式，可以自己实现Runable接口或者集成Thread类，或者使用jdk1.5以上提供了的Executors线程池。

3、springBoot异步执行方法@Async

首先创建一个普通的SpringBoot Web工程，添加web依赖即可。

<dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-web</artifactId>
            </dependency>

开启异步，@EnableAsync  注解主要是为了扫描范围包下的所有 @Async注解

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

创建异步任务，异步任务类代码：

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

@RestController
    public class AsyncTaskController {
    
        @Autowired
        private MyAsyncTask myAsyncTask;
    
        @RequestMapping
        public String doTask() throws InterruptedException {
            long currentTimeMillis = System.currentTimeMillis();
            myAsyncTask.task1();
            myAsyncTask.task2();
            myAsyncTask.task3();
            long currentTimeMillis1 = System.currentTimeMillis();
            System.out.println("task任务总耗时：" + (currentTimeMillis1 -currentTimeMillis));
    
            return "task任务总耗时：" + (currentTimeMillis1 -currentTimeMillis);
        }
    }

启动项目，访问接口，查看后台输出结果：

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L20wXzM3NzMyODI5_size_16_color_FFFFFF_t_70][]

4、采用Future来查看异步任务执行完毕和执行的结果

创建异步执行任务，异步代码块：

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

@RestController
    @RequestMapping
    public class FutureAsyncController {
    
        @Autowired
        private FutureAsyncTask futureAsyncTask;
    
        @RequestMapping("future/async")
        public String doTask() throws InterruptedException {
            long currentTimeMillis = System.currentTimeMillis();
    
            Future<String> task1 = futureAsyncTask.task1();
            Future<String> task2 = futureAsyncTask.task2();
            Future<String> task3 = futureAsyncTask.task3();
    
            while (true) {
                if(task1.isDone() && task2.isDone() && task3.isDone())
                    break;
            }
    
            long currentTimeMillis1 = System.currentTimeMillis();
            System.out.println("task任务总耗时：" + (currentTimeMillis1 -currentTimeMillis));
            return "task任务总耗时：" + (currentTimeMillis1 -currentTimeMillis);
        }
    }

启动项目，访问接口，查看后台输出结果：

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L20wXzM3NzMyODI5_size_16_color_FFFFFF_t_70 1][]

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[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L20wXzM3NzMyODI5_size_16_color_FFFFFF_t_70 1]: /images/20211219/4b7b244a59024ebe8b9410e879bb2a29.png