1. 需求
开发中我们经常遇到异步接口需要执行一些耗时的操作，并且接口要有返回结果。
使用场景：用户绑定邮箱、手机号，将邮箱、手机号保存入库后发送邮件或短信通知
接口要求：数据入库后给前台返回成功通知，后台异步执行发邮件、短信通知操作
一般的话在企业中会借用消息队列来实现发送，业务量大的话有一个统一消费、管理的地方。但有时项目中没有引用mq相关组件，这时为了实现一个功能去引用、维护一个消息组件有点大材小用，下面介绍几种不引用消息队列情况下的解决方式
定义线程池：
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.core.task.TaskExecutor;
import org.springframework.scheduling.annotation.EnableAsync;
import org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor;
import java.util.concurrent.ThreadPoolExecutor;
/**
* @description: 公共配置
* @author: yh
* @date: 2022/8/26
*/
@EnableAsync
@Configuration
public class CommonConfig {
@Bean
public TaskExecutor taskExecutor() {
ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();
// 设置核心线程数
executor.setCorePoolSize(50);
// 设置最大线程数
executor.setMaxPoolSize(200);
// 设置队列容量
executor.setQueueCapacity(200);
// 设置线程活跃时间（秒）
executor.setKeepAliveSeconds(800);
// 设置默认线程名称
executor.setThreadNamePrefix("task-");
// 设置拒绝策略
executor.setRejectedExecutionHandler(new ThreadPoolExecutor.CallerRunsPolicy());
// 等待所有任务结束后再关闭线程池
executor.setWaitForTasksToCompleteOnShutdown(true);
return executor;
}
}2. 解决方案
2.1 @Async
定义异步任务，如发送邮件、短信等
@Service
public class ExampleServiceImpl implements ExampleService {
@Async("taskExecutor")
@Override
public void sendMail(String email) {
try {
Thread.sleep(3000);
System.out.println("异步任务执行完成, " email " 当前线程：" Thread.currentThread().getName());
} catch (InterruptedException e) {
throw new RuntimeException(e);
}
}
}Controller
@RequestMapping(value = "/api")
@RestController
public class ExampleController {
@Resource
private ExampleService exampleService;
@RequestMapping(value = "/bind",method = RequestMethod.GET)
public String bind(@RequestParam("email") String email) {
long startTime = System.currentTimeMillis();
try {
// 绑定邮箱....业务
Thread.sleep(2000);
} catch (InterruptedException e) {
throw new RuntimeException(e);
}
//模拟异步任务(发邮件通知、短信等)
exampleService.sendMail(email);
long endTime = System.currentTimeMillis();
System.out.println("方法执行完成返回，耗时：" (endTime - startTime));
return "ok";
}
}运行结果：
2.2 TaskExecutor
@RequestMapping(value = "/api")
@RestController
public class ExampleController {
@Resource
private ExampleService exampleService;
@Resource
private TaskExecutor taskExecutor;
@RequestMapping(value = "/bind", method = RequestMethod.GET)
public String bind(@RequestParam("email") String email) {
long startTime = System.currentTimeMillis();
try {
// 绑定邮箱....业务
Thread.sleep(2000);
// 将发送邮件交给线程池去执行
taskExecutor.execute(() -> {
exampleService.sendMail(email);
});
} catch (InterruptedException e) {
throw new RuntimeException(e);
}
long endTime = System.currentTimeMillis();
System.out.println("方法执行完成返回，耗时：" (endTime - startTime));
return "ok";
}
}运行结果：
2.3 Future
首先去掉Service方法中的@Async("taskExecutor")，此时执行就会变成同步，总计需要5s才能完成接口返回。这次我们使用jdk1.8中的CompletableFuture来实现异步任务
@RequestMapping(value = "/api")
@RestController
public class ExampleController {
@Resource
private ExampleService exampleService;
@Resource
private TaskExecutor taskExecutor;
@RequestMapping(value = "/bind", method = RequestMethod.GET)
public String bind(@RequestParam("email") String email) {
long startTime = System.currentTimeMillis();
try {
// 绑定邮箱....业务
Thread.sleep(2000);
// 将发送邮件交给异步任务Future，需要记录返回值用supplyAsync
CompletableFuture.runAsync(() -> {
exampleService.sendMail(email);
}, taskExecutor);
} catch (InterruptedException e) {
throw new RuntimeException(e);
}
long endTime = System.currentTimeMillis();
System.out.println("方法执行完成返回，耗时：" (endTime - startTime));
return "ok";
}
}运行结果：
2.4 @EventListener
Spring为我们提供的一个事件监听、订阅的实现，内部实现原理是观察者设计模式；为的就是业务系统逻辑的解耦,提高可扩展性以及可维护性。事件发布者并不需要考虑谁去监听，监听具体的实现内容是什么，发布者的工作只是为了发布事件而已。
2.4.1 定义event事件模型
public class NoticeEvent extends ApplicationEvent {
private String email;
private String phone;
public NoticeEvent(Object source, String email, String phone) {
super(source);
this.email = email;
this.phone = phone;
}
public String getEmail() {
return email;
}
public void setEmail(String email) {
this.email = email;
}
public String getPhone() {
return phone;
}
public void setPhone(String phone) {
this.phone = phone;
}
}2.4.2 事件监听
@Component
public class ComplaintEventListener {
/**
* 只监听NoticeEvent事件
* @author: yh
* @date: 2022/8/27
*/
@Async
@EventListener(value = NoticeEvent.class)
// @Order(1) 指定事件执行顺序
public void sendEmail(NoticeEvent noticeEvent) {
//发邮件
try {
Thread.sleep(3000);
System.out.println("发送邮件任务执行完成, " noticeEvent.getEmail() " 当前线程：" Thread.currentThread().getName());
} catch (InterruptedException e) {
throw new RuntimeException(e);
}
}
@Async
@EventListener(value = NoticeEvent.class)
// @Order(2) 指定事件执行顺序
public void sendMsg(NoticeEvent noticeEvent) {
//发短信
try {
Thread.sleep(3000);
System.out.println("发送短信步任务执行完成, " noticeEvent.getPhone() " 当前线程：" Thread.currentThread().getName());
} catch (InterruptedException e) {
throw new RuntimeException(e);
}
}
}2.4.5 事件发布
@RequestMapping(value = "/api")
@RestController
public class ExampleController {
/**
* 用于事件推送
* @author: yh
* @date: 2022/8/27
*/
@Autowired
private ApplicationEventPublisher applicationEventPublisher;
@RequestMapping(value = "/bind", method = RequestMethod.GET)
public String bind(@RequestParam("email") String email) {
long startTime = System.currentTimeMillis();
try {
// 绑定邮箱....业务
Thread.sleep(2000);
// 发布事件，这里偷个懒手机号写死
applicationEventPublisher.publishEvent(new NoticeEvent(this, email, "13211112222"));
} catch (InterruptedException e) {
throw new RuntimeException(e);
}
long endTime = System.currentTimeMillis();
System.out.println("方法执行完成返回，耗时：" (endTime - startTime));
return "ok";
}
}运行结果：
3. 总结
通过@Async、子线程、Future异步任务、Spring自带ApplicationEvent事件监听都可以完成以上描述的需求。
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