要在springboot中使用异步调用方法,只要在被调用的方法上面加上@Async就可以了

准备一个springboot工程,在Application类上加上EnableAsync注解开启异步

/**
 * @Author: zgd
 * @Date: 18/09/12 10:27
 * @Description:
 */
@SpringBootApplication
@EnableAsync
public class Application {

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

}

这个注解如果不加,@Async注解失效

写一个同步接口和异步接口

package com.zgd.demo.thread.asyn.controller;

import com.zgd.demo.thread.asyn.service.HelloService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import java.time.Instant;

/**
 * @Author: zgd
 * @Date: 18/09/12 10:26
 * @Description: hello
 */
@RestController
@RequestMapping("/hello")
public class HelloController {

  @Autowired
  private HelloService helloService;

  /**
   * 异步方法
   * @return
   */
  @RequestMapping("/asyn")
  public String getAsynHello(){
    long n = Instant.now().toEpochMilli();
    //异步
    String s = helloService.asynchSayHello();

    long f = Instant.now().toEpochMilli();
    return s + " 时间: " + (f-n);

  }

  /**
   * 同步方法
   * * @return
   */
  @RequestMapping("/sync")
  public String getSyncHello(){

    long n = Instant.now().toEpochMilli();
    //异步
    String s = helloService.synchSayHello();

    long f = Instant.now().toEpochMilli();
    return s + " 时间: " + (f-n);
  }
}

写一个HelloService接口,并实现该接口

package com.zgd.demo.thread.asyn.service.impl;

import com.zgd.demo.thread.asyn.service.HelloService;
import com.zgd.demo.thread.asyn.service.SleepService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

/**
 * @Author: zgd
 * @Date: 18/09/12 10:43
 * @Description:
 */
@Service
public class HelloServiceImpl implements HelloService {

  @Autowired
  private SleepService sleepService;

  @Override
  public String synchSayHello() {
    try {
      sleepService.syncSleep();
      return "hello world,这是同步方法";
    } catch (InterruptedException e) {
      e.printStackTrace();
      return "error";
    }
  }

  @Override
  public String asynchSayHello() {
    try {
      System.out.println("主线程 "+Thread.currentThread().getName());
      sleepService.asyncSleep();
      return "hello world,这是异步方法";
    } catch (InterruptedException e) {
      e.printStackTrace();
      return "error";
    }
  }
}

这里为了模拟应用场景,将耗时的方法放在另一个service里面,就叫SleepService,同样的,实现这个接口

package com.zgd.demo.thread.asyn.service.impl;

import com.zgd.demo.thread.asyn.service.SleepService;
import org.springframework.scheduling.annotation.Async;
import org.springframework.stereotype.Service;

/**
 * @Author: zgd
 * @Date: 18/09/12 10:46
 * @Description:
 */
@Service
public class SleepServiceImpl implements SleepService {

  @Override
  public void syncSleep() throws InterruptedException {
    System.out.println("线程名: " +Thread.currentThread().getName());
    System.out.println("开始同步休眠3秒");
    Thread.sleep(3000);
    System.out.println("同步休眠结束");
  }

  @Override
  @Async
  public void asyncSleep() throws InterruptedException {
    System.out.println("次线程 "+Thread.currentThread().getName());

    System.out.println("开始异步休眠3秒");
    Thread.sleep(3000);
    System.out.println("异步休眠休眠结束");
  }
}

两个方法都是休眠3秒,aysncSleep方法上面有一个@Async注解

1. 必须要加@EnableAsync注解
2. 不能在同一类下调用@Async注解的方法,比如A类下有a和b方法,b方法有@Async注解,不能直接这样a调用b,要把b放到其他类中
3. @Async也可以打在类上,这样类下面的所有方法都是异步的(被其他类调用的时候)

如果我们没有使用springboot,使用传统的方法怎么异步调用方法?还是开启一个新的线程

增加一个接口

/**
   * 同步方法
   * * @return
   */
  @RequestMapping("/thread/asyn")
  public String getThreadSyncHello(){
    long n = Instant.now().toEpochMilli();
    //异步
    String s = helloService.threadAsynchSayHello();
    long f = Instant.now().toEpochMilli();
    return s + " 时间: " + (f-n);
  }

HelloServiceImpl

@Override
  public String threadAsynchSayHello() {
    //还是休眠3秒
    Runnable runnable = ()-> {
      try {
        sleepService.syncSleep();
      } catch (InterruptedException e) {
        e.printStackTrace();
      }
    };
    System.out.println(Thread.currentThread().getName()+"  开启新线程");
    new Thread(runnable).start();
    return "hello world,这是开启线程的异步方法";
  }