前言
本文主要给大家介绍了关于Spring Boot集成之异步调用Async的相关内容,分享出来供大家参考学习,下面话不多说了,来一起看看详细的介绍吧。
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。
异步处理方式
- 调用之后,不返回任何数据。
- 调用之后,返回数据,通过Future来获取返回数据
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:
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<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
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@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
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@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:
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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:
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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
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@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
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@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:
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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:
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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
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@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
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@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:
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task1任务耗时:1000ms task2任务耗时:2001ms task3任务耗时:3001ms |
浏览器输出:
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task任务总耗时:4015ms |
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!
总结
以上就是这篇文章的全部内容了,希望本文的内容对大家的学习或者工作具有一定的参考学习价值,如果有疑问大家可以留言交流,谢谢大家对服务器之家的支持。
原文链接:http://blog.csdn.net/v2sking/article/details/72795742