Spring 四种方式教你异步接口返回结果

富士山终究留不住欲落的樱花 🌺🌺🌺

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;
    }
}

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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);
        }
    }
}
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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";
    }
}
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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";
    }
}
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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";
    }
}
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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;
    }
}
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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);
        }
    }
}
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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";
    }
}
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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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