springboot 注解@Async实现异步调用

冷不防 2023-02-08 12:41 101阅读 0赞

### 文章目录 ###

*   *   *  1.模拟业务方法 并添加注解@Async
         *  2.在启动类增加@EnableAsync注解
         *  3.测试类与接口一
         *  4.结果比较
         *  5.使用AsyncResult接收异步执行结果
         *  6.测试类与接口二
         *  7.总结

### 1.模拟业务方法 并添加注解@Async ###

@Service
    public class TaskService {
        
        private static final Random random = new Random();
    
        @Async
        public void task1() {
        
            System.out.println("run task1 start...");
            long start = System.currentTimeMillis();
            try {
        
                Thread.sleep(random.nextInt(10000));
            } catch (InterruptedException e) {
        
                e.printStackTrace();
            }
            System.out.println("run task1 end..., time: " + (System.currentTimeMillis() - start) + " ms");
    
        }
    
        @Async
        public void task2() {
        
            System.out.println("run task2 start...");
            long start = System.currentTimeMillis();
            try {
        
                Thread.sleep(random.nextInt(10000));
            } catch (InterruptedException e) {
        
                e.printStackTrace();
            }
            System.out.println("run task2 end..., time: " + (System.currentTimeMillis() - start) + " ms");
        }
    
        @Async
        public void task3() {
        
            System.out.println("run task3 start...");
            long start = System.currentTimeMillis();
            try {
        
                Thread.sleep(random.nextInt(10000));
    
            } catch (InterruptedException e) {
        
                e.printStackTrace();
            }
            System.out.println("run task3 end..., time: " + (System.currentTimeMillis() - start) + " ms");
        }
    }

### 2.在启动类增加@EnableAsync注解 ###

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

### 3.测试类与接口一 ###

@RestController
    public class TestAsyncController {
        
        @Autowired
        private TaskService taskService;
    
        @GetMapping("test/async/task")
        public void testAsyncTask() {
        
            long start = System.currentTimeMillis();
            taskService.task1();
            taskService.task2();
            taskService.task3();
            System.out.println("run all task end: " + (System.currentTimeMillis() - start) + " ms");
        }
    }

### 4.结果比较 ###

// task任务不加 @Async 的日志打印
    run task1 start...
    run task1 end..., time: 3739 ms
    run task2 start...
    run task2 end..., time: 8025 ms
    run task3 start...
    run task3 end..., time: 9057 ms
    run all task end: 20821 ms
    
    // task任务加 @Async 的日志打印 主任务先结束
    run all task end: 4 ms
    run task1 start...
    run task2 start...
    run task3 start...
    run task3 end..., time: 1095 ms
    run task2 end..., time: 4952 ms
    run task1 end..., time: 8442 ms

### 5.使用AsyncResult接收异步执行结果 ###

@Service
    public class TaskService {
        
        private static final Random random = new Random();
    
        @Async
        public Future<String> task1() {
        
            System.out.println("run task1 start...");
            long start = System.currentTimeMillis();
            try {
        
                Thread.sleep(random.nextInt(10000));
            } catch (InterruptedException e) {
        
                e.printStackTrace();
            }
            System.out.println("run task1 end..., time: " + (System.currentTimeMillis() - start) + " ms");
    
            return new AsyncResult<>("task1 result");
        }
    
        @Async
        public Future<String> task2() {
        
            System.out.println("run task2 start...");
            long start = System.currentTimeMillis();
            try {
        
                Thread.sleep(random.nextInt(10000));
            } catch (InterruptedException e) {
        
                e.printStackTrace();
            }
            System.out.println("run task2 end..., time: " + (System.currentTimeMillis() - start) + " ms");
            return new AsyncResult<>("task2 result");
        }
    
        @Async
        public Future<String> task3() {
        
            System.out.println("run task3 start...");
            long start = System.currentTimeMillis();
            try {
        
                Thread.sleep(random.nextInt(10000));
    
            } catch (InterruptedException e) {
        
                e.printStackTrace();
            }
            System.out.println("run task3 end..., time: " + (System.currentTimeMillis() - start) + " ms");
            return new AsyncResult<>("task3 result");
        }
    }

### 6.测试类与接口二 ###

@RestController
    public class TestAsyncController {
        
        @Autowired
        private TaskService taskService;
    
        @GetMapping("test/async/task")
        public void testAsyncTask() {
        
            long start = System.currentTimeMillis();
            Future<String> future1 = taskService.task1();
            Future<String> future2 = taskService.task2();
            Future<String> future3 = taskService.task3();
            while (true) {
        
                if (future1.isDone() && future2.isDone() && future3.isDone()) {
        
                    System.out.println(future1.get());
                    System.out.println(future2.get());
                    System.out.println(future3.get());
                    break;
                }
                TimeUnit.MICROSECONDS.sleep(500);
            }
            System.out.println("run all task end: " + (System.currentTimeMillis() - start) + " ms");
        }
    }

### 7.总结 ###

1.  使用@Async注解的方法task1 task2 task3是异步调用的
2.  使用@Async在主任务先结束，但主任务需要获取task1 task2 task3的执行结果的场景中不适用，需要配合AsyncResult实现(查看AsyncResult的源码，会发现它实现了`Future<T>`)
3.  @Async所修饰的函数不要定义为static类型，这样异步调用不会生效