千万不要这样使用@Async注解

来自：chuckfang.com/2019/11/13/Async

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.scheduling.annotation.EnableAsync;

@SpringBootApplication
@EnableAsync
public class AsyncdemoApplication {

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

}

import org.springframework.scheduling.annotation.Async;
import org.springframework.stereotype.Component;

import java.util.Random;

/**
 * @author https://www.chuckfang.top
 * @date Created on 2019/11/12 11:34
 */
@Component
public class Task {

    public static Random random = new Random();

    @Async
    public void doTaskOne() throws Exception {
        System.out.println("开始做任务一");
        long start = System.currentTimeMillis();
        Thread.sleep(random.nextInt(10000));
        long end = System.currentTimeMillis();
        System.out.println("完成任务一，耗时：" + (end - start) + "毫秒");
    }

    @Async
    public void doTaskTwo() throws Exception {
        System.out.println("开始做任务二");
        long start = System.currentTimeMillis();
        Thread.sleep(random.nextInt(10000));
        long end = System.currentTimeMillis();
        System.out.println("完成任务二，耗时：" + (end - start) + "毫秒");
    }

    @Async
    public void doTaskThree() throws Exception {
        System.out.println("开始做任务三");
        long start = System.currentTimeMillis();
        Thread.sleep(random.nextInt(10000));
        long end = System.currentTimeMillis();
        System.out.println("完成任务三，耗时：" + (end - start) + "毫秒");
    }
}

@SpringBootTest
class AsyncdemoApplicationTests {

    public static Random random = new Random();

    @Autowired
    Task task;

    @Test
    void contextLoads() throws Exception {
        task.doTaskOne();
        task.doTaskTwo();
        task.doTaskThree();
        Thread.sleep(10000);
    }
}

❝

开始做任务三 开始做任务二 开始做任务一 完成任务一，耗时：4922毫秒 完成任务三，耗时：6778毫秒 完成任务二，耗时：6960毫秒

❞

@SpringBootTest
class AsyncdemoApplicationTests {

    public static Random random = new Random();

    @Test
    void contextLoads() throws Exception {
        doTaskOne();
        doTaskTwo();
        doTaskThree();
        Thread.sleep(10000);
    }

    @Async
    public void doTaskOne() throws Exception {
        System.out.println("开始做任务一");
        long start = System.currentTimeMillis();
        Thread.sleep(random.nextInt(10000));
        long end = System.currentTimeMillis();
        System.out.println("完成任务一，耗时：" + (end - start) + "毫秒");
    }

    @Async
    public void doTaskTwo() throws Exception {
        System.out.println("开始做任务二");
        long start = System.currentTimeMillis();
        Thread.sleep(random.nextInt(10000));
        long end = System.currentTimeMillis();
        System.out.println("完成任务二，耗时：" + (end - start) + "毫秒");
    }

    @Async
    public void doTaskThree() throws Exception {
        System.out.println("开始做任务三");
        long start = System.currentTimeMillis();
        Thread.sleep(random.nextInt(10000));
        long end = System.currentTimeMillis();
        System.out.println("完成任务三，耗时：" + (end - start) + "毫秒");
    }
}

❝

开始做任务一 完成任务一，耗时：9284毫秒 开始做任务二 完成任务二，耗时：8783毫秒 开始做任务三 完成任务三，耗时：943毫秒

❞

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First – let’s go over the rules – @Async has two limitations:

• it must be applied to public methods only
• self-invocation – calling the async method from within the same class – won’t work

The reasons are simple – 「the method needs to be *public*」 so that it can be proxied. And 「self-invocation doesn’t work」 because it bypasses the proxy and calls the underlying method directly.

❞