Spring Boot使用@Async实现异步调用

原文：http://blog.csdn.net/a286352250/article/details/53157822

项目GitHub地址：

https://github.com/FrameReserve/TrainingBoot

Spring Boot（十）使用@Async实现异步调用，标记地址：

https://github.com/FrameReserve/TrainingBoot/releases/tag/0.0.10

Spring Boot启动类，增加@EnableAsync注解配置：

src/main/java/com/training/SpringBootServlet.java

package com.training;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.builder.SpringApplicationBuilder;
import org.springframework.boot.web.support.SpringBootServletInitializer;
import org.springframework.scheduling.annotation.EnableAsync;
@SpringBootApplication
@EnableAsync
public class SpringBootServlet extends SpringBootServletInitializer {
// jar启动
public static void main(String[] args) {
SpringApplication.run(SpringBootServlet.class, args);
}
// tomcat war启动
@Override
protected SpringApplicationBuilder configure(SpringApplicationBuilder application) {
return application.sources(SpringBootServlet.class);
}
}

测试：

增加异步方法Service，线程休眠：

package com.training.async.service.impl;
import java.util.Random;
import java.util.concurrent.Future;
import org.springframework.scheduling.annotation.Async;
import org.springframework.scheduling.annotation.AsyncResult;
import org.springframework.stereotype.Service;
import com.training.async.service.DemoAsyncService;
@Service
public class DemoAsyncServiceImpl implements DemoAsyncService {
public static Random random =new Random();
@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");
}
}

调用异步测试测试，查看控制台输出执行顺序：

package com.training.async.controller;
import io.swagger.annotations.ApiOperation;
import java.util.concurrent.Future;
import javax.annotation.Resource;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.bind.annotation.RestController;
import com.training.async.service.DemoAsyncService;
import com.training.core.dto.ResultDataDto;
@RestController
@RequestMapping(value="/async")
public class DemoAsyncController {
@Resource
private DemoAsyncService demoAsyncService;
/**
* 测试异步方法调用顺序
*/
@ApiOperation(value="测试异步方法调用顺序", notes="getEntityById")
@RequestMapping(value = "/getTestDemoAsync", method = RequestMethod.GET)
public @ResponseBody ResultDataDto getEntityById() throws Exception {
long start = System.currentTimeMillis();
Future<String> task1 = demoAsyncService.doTaskOne();
Future<String> task2 = demoAsyncService.doTaskTwo();
Future<String> task3 = demoAsyncService.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");
return ResultDataDto.addSuccess();
}
}

原文：http://blog.csdn.net/v2sking/article/details/72795742

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。

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。

StrngBoot中则提供了很方便的方式执行异步调用。

按照官方示例开撸

代码入下

maven依赖：

<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>1.5.3.RELEASE</version>
</parent>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
</dependencies>

启动类：添加@EnableAsync注解

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

Controller

只需在需要异步执行方法上添加@Async注解

@RestController
@RequestMapping("")
public class AsyncTaskController {
@RequestMapping("")
public String doTask() throws InterruptedException{
long currentTimeMillis = System.currentTimeMillis();
this.task1();
this.task2();
this.task3();
long currentTimeMillis1 = System.currentTimeMillis();
return "task任务总耗时:"+(currentTimeMillis1-currentTimeMillis)+"ms";
}
@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)+"ms");
}
@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)+"ms");
}
@Async
public void task3() throws InterruptedException{
long currentTimeMillis = System.currentTimeMillis();
Thread.sleep(3000);
long currentTimeMillis1 = System.currentTimeMillis();
System.out.println("task3任务耗时:"+(currentTimeMillis1-currentTimeMillis)+"ms");
}
}

main函数运行spirngboot项目，启动完成后浏览器访问：

http://localhost:8080/

控制台：

task1任务耗时:1012ms
task2任务耗时:2009ms
task3任务耗时:3004ms

等了一段浏览器时候输出入下：

task任务总耗时:6002ms

异步并没有执行！

难道是代码写错了？反复检查了好几遍，并没有发现什么明显错误，想起spring对@Transactional注解时也有类似问题，spring扫描时具有@Transactional注解方法的类时，是生成一个代理类，由代理类去开启关闭事务，而在同一个类中，方法调用是在类体内执行的，spring无法截获这个方法调用。

豁然开朗，将异步任务单独放到一个类中，调整代码入下：

Controller

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

异步任务类

@Component
public class AsyncTask {
@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)+"ms");
}
@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)+"ms");
}
@Async
public void task3() throws InterruptedException{
long currentTimeMillis = System.currentTimeMillis();
Thread.sleep(3000);
long currentTimeMillis1 = System.currentTimeMillis();
System.out.println("task3任务耗时:"+(currentTimeMillis1-currentTimeMillis)+"ms");
}
}

控制台：

task1任务耗时:1012ms
task2任务耗时:2009ms
task3任务耗时:3004ms

访问浏览器结果入下：

task任务总耗时:19ms

异步调用成功！

如何知道三个异步任务什么时候执行完，执行的结果怎样呢？可以采用添加Fature回调方式判断

代码入下：

异步任务类

@Component
public class AsyncTask {
@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)+"ms");
return new AsyncResult<String>("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)+"ms");
return new AsyncResult<String>("task2执行完毕");
}
@Async
public Future<String> task3() throws InterruptedException{
long currentTimeMillis = System.currentTimeMillis();
Thread.sleep(3000);
long currentTimeMillis1 = System.currentTimeMillis();
System.out.println("task3任务耗时:"+(currentTimeMillis1-currentTimeMillis)+"ms");
return new AsyncResult<String>("task3执行完毕");
}
}

Controller

@RequestMapping("")
@RestController
public class AsyncTaskController {
@Autowired
private AsyncTask asyncTask;
@RequestMapping("")
public String doTask() throws InterruptedException{
long currentTimeMillis = System.currentTimeMillis();
Future<String> task1 = asyncTask.task1();
Future<String> task2 = asyncTask.task2();
Future<String> task3 = asyncTask.task3();
String result = null;
for (;;) {
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 currentTimeMillis1 = System.currentTimeMillis();
result = "task任务总耗时:"+(currentTimeMillis1-currentTimeMillis)+"ms";
return result;
}
}

控制台输出：

task1任务耗时:1000ms
task2任务耗时:2001ms
task3任务耗时:3001ms

浏览器输出：

<span style="font-family: Simsun; font-size: 14px;">task任务总耗时:4015ms</span>

异步调用成功，并且在所有任务都完成时程序才返回了结果！

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Spring Boot使用@Async实现异步调用

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