博客

一 点睛

1 什么是“异步调用”

“异步调用”对应的是“同步调用”，同步调用指程序按照定义顺序依次执行，每一行程序都必须等待上一行程序执行完成之后才能执行；异步调用指程序在顺序执行时，不等待异步调用的语句返回结果就执行后面的程序。

二 实战

1 新建pom

<dependencies>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-test</artifactId>
        <scope>test</scope>
    </dependency>
</dependencies>

2 定义异步任务

package com.didispace.async;

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

import java.util.Random;
import java.util.concurrent.Future;


@Component
public class Task {

    public static Random random =new Random();

    //在Spring Boot中，只需要通过使用@Async注解就能简单的将原来的同步函数变为异步函数
    @Async
    public Future<String> 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");
        return new AsyncResult<>("任务一完成");
    }

    @Async
    public Future<String> 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");
        return new AsyncResult<>("任务二完成");
    }

    @Async
    public Future<String> 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");
        return new AsyncResult<>("任务三完成");
    }

}

3 启动类

package com.didispace;

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

@SpringBootApplication
//为了让@Async注解能够生效，还需要在Spring Boot的主程序中配置@EnableAsync
@EnableAsync
public class Application {

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

}

4 测试类

package com.didispace;

import com.didispace.async.Task;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.SpringApplicationConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;

import java.util.concurrent.Future;


@RunWith(SpringJUnit4ClassRunner.class)
@SpringApplicationConfiguration(classes = Application.class)
public class ApplicationTests {

    @Autowired
    private Task task;

    @Test
    public void test() throws Exception {

        long start = System.currentTimeMillis();

        Future<String> task1 = task.doTaskOne();
        Future<String> task2 = task.doTaskTwo();
        Future<String> task3 = task.doTaskThree();

        while(true) {
            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 end = System.currentTimeMillis();

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

    }

}

三 测试结果

开始做任务一

开始做任务二

开始做任务三

完成任务二，耗时：1065毫秒

完成任务三，耗时：8209毫秒

完成任务一，耗时：9563毫秒

任务全部完成，总耗时：10012毫秒

四 参考

http://blog.didispace.com/springbootasync/