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SpringBoot执行有返回值的异步任务问题

作者:章鱼先森cd

这篇文章主要介绍了SpringBoot执行有返回值的异步任务问题,具有很好的参考价值,希望对大家有所帮助。如有错误或未考虑完全的地方,望不吝赐教

SpringBoot执行有返回值异步任务

Springboot如何使用多线程处理异步任务,并且是代返回值的。

比如,我一个Controller层的接口,调用到Service层,在对应的Service方法中有三个方法,这三个方法都是去调Dao层查询数据库数据,每个查询平均耗时5s,最后将这三个查询的结果进行合并计算。如果不采用异步查询的至少需要15s的时间来处理这个请求。此时我们可以使用异步任务方式来操作,可以减少10s左右的时间。

在Springboot中使用异步需要开启异步支持(@EnableAsync),代码如下

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

然后增加一个配置类,不过这个Springboot也会默认配置,一般我们使用线程池是都不使用默认的,而是使用自定义的:

/**
 * @author Mr. Zhang
 * @description 异步线程池
 * @date 2019-04-19 14:21
 * @website https://www.zhangguimin.cn
 */
@Configuration
public class AsyncConfig {
    private static final int THREADS = Runtime.getRuntime().availableProcessors();
    @Bean("taskExecutor")
    public Executor execute() {
        System.out.println(THREADS);
        Executor executor = new ThreadPoolExecutor(THREADS, 2 * THREADS, 5, TimeUnit.SECONDS, new LinkedBlockingQueue<>(1024));
        return executor;
    }
}

此配置为IO密集型服务器参数,即最大线程数为CPU核数*2(THREADS为CPU核数),其他拒绝策略默认即可。

在之后的异步任务中使用此出定义的线程池taskExecutor。

然后就是异步任务,在对应的任务方法上标注@Async(“taskExecutor”)即可,表示使用taskExecutor线程池中线程执行异步任务。代码参考:

@Service
public class TaskServer {
    @Async("taskExecutor")
    public Future<Integer> asyncTask(CountDownLatch latch) {
        try {
            Thread.sleep(3000L);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }finally {
            latch.countDown();
        }
        return new AsyncResult<>(10);
    }
    @Async("taskExecutor")
    public Future<Integer> asyncTask2(CountDownLatch latch) {
        try {
            Thread.sleep(3000L);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }finally {
            latch.countDown();
        }
        return new AsyncResult<>(20);
    }
    @Async("taskExecutor")
    public Future<Integer> asyncTask3(CountDownLatch latch) {
        try {
            Thread.sleep(3000L);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }finally {
            latch.countDown();
        }
        return new AsyncResult<>(30);
    }
}

注意的是,需要在类上标注为组件注解,此处为@Service。

在这三个方法中执行sleep,使线程都是sleep 3秒的时间。然后参数为CountDownLatch,在每次执行完就countDown(),然后返回值为Future,如果执行的异步方法没有返回值可以不需要CountDownLatch和返回值就行。

在对应的测试类中执行

@RunWith(SpringRunner.class)
@SpringBootTest
public class PublisherApplicationTests {
    @Autowired
    private TaskServer taskServer;
    @Test
    public void test() {
        CountDownLatch latch = new CountDownLatch(3);
        LocalTime time = LocalTime.now();
        Future<Integer> integerFuture = taskServer.asyncTask(latch);
        Future<Integer> integerFuture1 = taskServer.asyncTask2(latch);
        Future<Integer> integerFuture2 = taskServer.asyncTask3(latch);
        try {
            latch.await();
            LocalTime end =LocalTime.now();
            System.out.println(Duration.between(time, end));
            Integer integer = integerFuture.get();
            Integer integer1 = integerFuture1.get();
            Integer integer2 = integerFuture2.get();
            int i = integer + integer1 + integer2;
            System.out.println(i);
        } catch (InterruptedException e) {
            e.printStackTrace();
        } catch (ExecutionException e) {
            e.printStackTrace();
        }
    }
}

注意CountDownLatch latch = new CountDownLatch(3);有三个异步方法传入的值为3,在调用的异步方法后面需要latch.await();

一定不要在latch.await();前去get()结果值,这样会导致异步方法强制执行。

另外,有的人也使用while循环,在所有结果出来前一致在循环等待,类似自旋锁的原理,对资源消耗较高,还有,如果一个任务出现错误,就可能会造成一只循环。而CountDownLatch可在await()方法中传入等待时间,如果超过这个时间就会结束等待,直接完成下面的操作。

SpringBoot开启有返回值的异步调用:三步搞定

1、线程池配置

package com.listen.demo.config;
/**
 * @author liuxd
 * @version 1.0
 * @date 2019-12-25 15:46
 */
import com.listen.demo.service.MyTaskServer;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.scheduling.annotation.EnableAsync;
import org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor;
import java.util.concurrent.Executor;
import java.util.concurrent.ThreadPoolExecutor;
@Configuration
//@ComponentScan({"com.listen.demo"})
@EnableAsync
public class ExecutorConfig {
    private static final Logger logger = LoggerFactory.getLogger(ExecutorConfig.class);
    @Bean
    public Executor asyncServiceExecutor() {
        logger.info("start asyncServiceExecutor");
        ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();
        //配置核心线程数
        executor.setCorePoolSize(5);
        //配置最大线程数
        executor.setMaxPoolSize(5);
        //配置队列大小
        executor.setQueueCapacity(99999);
        //配置线程池中的线程的名称前缀
        executor.setThreadNamePrefix("async-service-");
        // rejection-policy:当pool已经达到max size的时候,如何处理新任务
        // CALLER_RUNS:不在新线程中执行任务,而是有调用者所在的线程来执行
        executor.setRejectedExecutionHandler(new ThreadPoolExecutor.CallerRunsPolicy());
        //执行初始化
        executor.initialize();
        return executor;
    }
    @Bean
    public MyTaskServer myTaskServer(){
        return new MyTaskServer();
    }
}

2、业务操作类

package com.listen.demo.service;
import org.springframework.scheduling.annotation.Async;
import org.springframework.scheduling.annotation.AsyncResult;
import org.springframework.stereotype.Service;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.Future;
/**
 * @author liuxd
 * @version 1.0
 * @date 2019-12-25 15:48
 */
@Service
public class MyTaskServer {
    @Async("asyncServiceExecutor")
    public Future<Integer> asyncTask(CountDownLatch countDownLatch) throws Exception {
        Thread.sleep(1000L);
        countDownLatch.countDown();
        return new AsyncResult<>(10);
    }
    @Async("asyncServiceExecutor")
    public Future<Integer> asyncTask2(CountDownLatch countDownLatch) throws Exception {
        Thread.sleep(2000L);
        countDownLatch.countDown();
        return new AsyncResult<>(20);
    }
    @Async("asyncServiceExecutor")
    public Future<Integer> asyncTask3(CountDownLatch countDownLatch) throws Exception {
        Thread.sleep(3000L);
        countDownLatch.countDown();
        return new AsyncResult<>(30);
    }
}
 

3、异步+等待+有返回的测试类

package com.listen.demo;
import com.listen.demo.config.ExecutorConfig;
import com.listen.demo.service.MyTaskServer;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.Future;
/**
 * @author liuxd
 * @version 1.0
 * @date 2019-12-25 16:03
 */
public class TestAsyncTask {
    public static void main(String[] args) throws Exception {
        System.out.println("主线程:" + Thread.currentThread().getName() + "开始执行调用任务...");
        AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(ExecutorConfig.class);
        MyTaskServer myTaskServer = context.getBean(MyTaskServer.class);
        CountDownLatch countDownLatch = new CountDownLatch(3);
        Future<Integer> future1 = myTaskServer.asyncTask(countDownLatch);
        Future<Integer> future2 = myTaskServer.asyncTask2(countDownLatch);
        Future<Integer> future3 = myTaskServer.asyncTask3(countDownLatch);
        countDownLatch.await();
        Integer num1 = future1.get();
        Integer num2 = future2.get();
        Integer num3 = future3.get();
        int data = num1 + num2 + num3;
        System.out.println("最终汇总计算结果:" + data);
        context.close();
        try {
            Thread.sleep(1000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        System.out.println("主线程:" + Thread.currentThread().getName() + "程序结束!!");
    }
}

总结

以上为个人经验,希望能给大家一个参考,也希望大家多多支持脚本之家。

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