java 异步线程池

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转载最新推荐文章于 2026-04-10 20:57:20 发布 2k 阅读 AI 写同款· GEO 优化 ›

Java线程池的拒绝策略拒绝策略被设置为CallerRunsPolicy，即当任务被拒绝时，由提交任务的线程来执行该任务。这是线程池默认的拒绝策略。在这个示例中，我们创建了一个线程池，并设置核心线程数为2，最大线程数为4，使用有界队列（大小为3）。DiscardOldestPolicy：当任务被拒绝时，丢弃队列中最老的一个任务，并尝试再次提交被拒绝的任务。，这意味着当线程池无法处理新的任务时，会丢弃队列中的最早的任务，并尝试将新的任务添加到队列中。，这意味着当线程池无法处理新的任务时，会默默地丢弃被拒绝的任务，不抛出任何异常。阅读详情

https://www.jb51.net/article/180986.htm

https://www.cnblogs.com/alimayun/p/10934202.html

springboot线程池的使用和扩展

文章出处：https://www.cnblogs.com/pejsidney/p/9001875.html

我们常用ThreadPoolExecutor提供的线程池服务，springboot框架提供了@Async注解，帮助我们更方便的将业务逻辑提交到线程池中异步执行，今天我们就来实战体验这个线程池服务；

本文地址：http://blog.youkuaiyun.com/boling_cavalry/article/details/79120268

实战环境

windowns10；
jdk1.8；
springboot 1.5.9.RELEASE；
开发工具：IntelliJ IDEA；

实战源码

本次实战的源码可以在我的GitHub下载，地址：git@github.com:zq2599/blog_demos.git，项目主页：https://github.com/zq2599/blog_demos

这里面有多个工程，本次用到的工程为threadpooldemoserver，如下图红框所示：
这里写图片描述

实战步骤梳理

本次实战的步骤如下：
1. 创建springboot工程；
2. 创建Service层的接口和实现；
3. 创建controller，开发一个http服务接口，里面会调用service层的服务；
4. 创建线程池的配置；
5. 将Service层的服务异步化，这样每次调用都会都被提交到线程池异步执行；
6. 扩展ThreadPoolTaskExecutor，在提交任务到线程池的时候可以观察到当前线程池的情况；

创建springboot工程

用IntelliJ IDEA创建一个springboot的web工程threadpooldemoserver，pom.xml内容如下：

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>com.bolingcavalry</groupId>
    <artifactId>threadpooldemoserver</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>
    <name>threadpooldemoserver</name>
    <description>Demo project for Spring Boot</description>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>1.5.9.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
        <java.version>1.8</java.version>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
    </dependencies>
    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>
</project>

创建Service层的接口和实现

创建一个service层的接口AsyncService，如下：

public interface AsyncService {

    /**
     * 执行异步任务
     */
    void executeAsync();
}

对应的AsyncServiceImpl，实现如下：

@Service
public class AsyncServiceImpl implements AsyncService {

    private static final Logger logger = LoggerFactory.getLogger(AsyncServiceImpl.class);

    @Override
    public void executeAsync() {
        logger.info("start executeAsync");
        try{
            Thread.sleep(1000);
        }catch(Exception e){
            e.printStackTrace();
        }
        logger.info("end executeAsync");
    }
}

这个方法做的事情很简单：sleep了一秒钟；

创建controller

创建一个controller为Hello，里面定义一个http接口，做的事情是调用Service层的服务，如下：

@RestController
public class Hello {

    private static final Logger logger = LoggerFactory.getLogger(Hello.class);

    @Autowired
    private AsyncService asyncService;

    @RequestMapping("/")
    public String submit(){
        logger.info("start submit");

        //调用service层的任务
        asyncService.executeAsync();

        logger.info("end submit");

        return "success";
    }
}

至此，我们已经做好了一个http请求的服务，里面做的事情其实是同步的，接下来我们就开始配置springboot的线程池服务，将service层做的事情都提交到线程池中去处理；

springboot的线程池配置

创建一个配置类ExecutorConfig，用来定义如何创建一个ThreadPoolTaskExecutor，要使用@Configuration和@EnableAsync这两个注解，表示这是个配置类，并且是线程池的配置类，如下所示：

@Configuration
@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;
    }
}

注意，上面的方法名称为asyncServiceExecutor，稍后马上用到；

将Service层的服务异步化

打开AsyncServiceImpl.java，在executeAsync方法上增加注解@Async(“asyncServiceExecutor”)，asyncServiceExecutor是前面ExecutorConfig.java中的方法名，表明executeAsync方法进入的线程池是asyncServiceExecutor方法创建的，如下：

@Override
    @Async("asyncServiceExecutor")
    public void executeAsync() {
        logger.info("start executeAsync");
        try{
            Thread.sleep(1000);
        }catch(Exception e){
            e.printStackTrace();
        }
        logger.info("end executeAsync");
    }

验证效果

将这个springboot运行起来（pom.xml所在文件夹下执行mvn spring-boot:run）；
在浏览器输入：http://localhost:8080；
在浏览器用F5按钮快速多刷新几次；
在springboot的控制台看见日志如下：

2018-01-21 22:43:18.630  INFO 14824 --- [nio-8080-exec-8] c.b.t.controller.Hello                   : start submit
2018-01-21 22:43:18.630  INFO 14824 --- [nio-8080-exec-8] c.b.t.controller.Hello                   : end submit
2018-01-21 22:43:18.929  INFO 14824 --- [async-service-1] c.b.t.service.impl.AsyncServiceImpl      : end executeAsync
2018-01-21 22:43:18.930  INFO 14824 --- [async-service-1] c.b.t.service.impl.AsyncServiceImpl      : start executeAsync
2018-01-21 22:43:19.005  INFO 14824 --- [async-service-2] c.b.t.service.impl.AsyncServiceImpl      : end executeAsync
2018-01-21 22:43:19.006  INFO 14824 --- [async-service-2] c.b.t.service.impl.AsyncServiceImpl      : start executeAsync
2018-01-21 22:43:19.175  INFO 14824 --- [async-service-3] c.b.t.service.impl.AsyncServiceImpl      : end executeAsync
2018-01-21 22:43:19.175  INFO 14824 --- [async-service-3] c.b.t.service.impl.AsyncServiceImpl      : start executeAsync
2018-01-21 22:43:19.326  INFO 14824 --- [async-service-4] c.b.t.service.impl.AsyncServiceImpl      : end executeAsync
2018-01-21 22:43:19.495  INFO 14824 --- [async-service-5] c.b.t.service.impl.AsyncServiceImpl      : end executeAsync
2018-01-21 22:43:19.930  INFO 14824 --- [async-service-1] c.b.t.service.impl.AsyncServiceImpl      : end executeAsync
2018-01-21 22:43:20.006  INFO 14824 --- [async-service-2] c.b.t.service.impl.AsyncServiceImpl      : end executeAsync
2018-01-21 22:43:20.191  INFO 14824 --- [async-service-3] c.b.t.service.impl.AsyncServiceImpl      : end executeAsync

如上日志所示，我们可以看到controller的执行线程是”nio-8080-exec-8”，这是tomcat的执行线程，而service层的日志显示线程名为“async-service-1”，显然已经在我们配置的线程池中执行了，并且每次请求中，controller的起始和结束日志都是连续打印的，表明每次请求都快速响应了，而耗时的操作都留给线程池中的线程去异步执行；

扩展ThreadPoolTaskExecutor

虽然我们已经用上了线程池，但是还不清楚线程池当时的情况，有多少线程在执行，多少在队列中等待呢？这里我创建了一个ThreadPoolTaskExecutor的子类，在每次提交线程的时候都会将当前线程池的运行状况打印出来，代码如下：

public class VisiableThreadPoolTaskExecutor extends ThreadPoolTaskExecutor {
    private static final Logger logger = LoggerFactory.getLogger(VisiableThreadPoolTaskExecutor.class);

    private void showThreadPoolInfo(String prefix){
        ThreadPoolExecutor threadPoolExecutor = getThreadPoolExecutor();

        if(null==threadPoolExecutor){
            return;
        }

        logger.info("{}, {},taskCount [{}], completedTaskCount [{}], activeCount [{}], queueSize [{}]",
                this.getThreadNamePrefix(),
                prefix,
                threadPoolExecutor.getTaskCount(),
                threadPoolExecutor.getCompletedTaskCount(),
                threadPoolExecutor.getActiveCount(),
                threadPoolExecutor.getQueue().size());
    }

    @Override
    public void execute(Runnable task) {
        showThreadPoolInfo("1. do execute");
        super.execute(task);
    }

    @Override
    public void execute(Runnable task, long startTimeout) {
        showThreadPoolInfo("2. do execute");
        super.execute(task, startTimeout);
    }

    @Override
    public Future<?> submit(Runnable task) {
        showThreadPoolInfo("1. do submit");
        return super.submit(task);
    }

    @Override
    public <T> Future<T> submit(Callable<T> task) {
        showThreadPoolInfo("2. do submit");
        return super.submit(task);
    }

    @Override
    public ListenableFuture<?> submitListenable(Runnable task) {
        showThreadPoolInfo("1. do submitListenable");
        return super.submitListenable(task);
    }

    @Override
    public <T> ListenableFuture<T> submitListenable(Callable<T> task) {
        showThreadPoolInfo("2. do submitListenable");
        return super.submitListenable(task);
    }
}

如上所示，showThreadPoolInfo方法中将任务总数、已完成数、活跃线程数，队列大小都打印出来了，然后Override了父类的execute、submit等方法，在里面调用showThreadPoolInfo方法，这样每次有任务被提交到线程池的时候，都会将当前线程池的基本情况打印到日志中；

修改ExecutorConfig.java的asyncServiceExecutor方法，将ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor()改为ThreadPoolTaskExecutor executor = new VisiableThreadPoolTaskExecutor()，如下所示：

@Bean
    public Executor asyncServiceExecutor() {
        logger.info("start asyncServiceExecutor");
        //使用VisiableThreadPoolTaskExecutor
        ThreadPoolTaskExecutor executor = new VisiableThreadPoolTaskExecutor();
        //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;
    }

再次启动该工程，再浏览器反复刷新http://localhost:8080，看到的日志如下：

2018-01-21 23:04:56.113  INFO 15580 --- [nio-8080-exec-1] c.b.t.e.VisiableThreadPoolTaskExecutor   : async-service-, 2. do submit,taskCount [99], completedTaskCount [85], activeCount [5], queueSize [9]
2018-01-21 23:04:56.113  INFO 15580 --- [nio-8080-exec-1] c.b.t.controller.Hello                   : end submit
2018-01-21 23:04:56.225  INFO 15580 --- [async-service-1] c.b.t.service.impl.AsyncServiceImpl      : end executeAsync
2018-01-21 23:04:56.225  INFO 15580 --- [async-service-1] c.b.t.service.impl.AsyncServiceImpl      : start executeAsync
2018-01-21 23:04:56.240  INFO 15580 --- [nio-8080-exec-2] c.b.t.controller.Hello                   : start submit
2018-01-21 23:04:56.240  INFO 15580 --- [nio-8080-exec-2] c.b.t.e.VisiableThreadPoolTaskExecutor   : async-service-, 2. do submit,taskCount [100], completedTaskCount [86], activeCount [5], queueSize [9]
2018-01-21 23:04:56.240  INFO 15580 --- [nio-8080-exec-2] c.b.t.controller.Hello                   : end submit
2018-01-21 23:04:56.298  INFO 15580 --- [async-service-2] c.b.t.service.impl.AsyncServiceImpl      : end executeAsync
2018-01-21 23:04:56.298  INFO 15580 --- [async-service-2] c.b.t.service.impl.AsyncServiceImpl      : start executeAsync
2018-01-21 23:04:56.372  INFO 15580 --- [nio-8080-exec-3] c.b.t.controller.Hello                   : start submit
2018-01-21 23:04:56.373  INFO 15580 --- [nio-8080-exec-3] c.b.t.e.VisiableThreadPoolTaskExecutor   : async-service-, 2. do submit,taskCount [101], completedTaskCount [87], activeCount [5], queueSize [9]
2018-01-21 23:04:56.373  INFO 15580 --- [nio-8080-exec-3] c.b.t.controller.Hello                   : end submit
2018-01-21 23:04:56.444  INFO 15580 --- [async-service-3] c.b.t.service.impl.AsyncServiceImpl      : end executeAsync
2018-01-21 23:04:56.445  INFO 15580 --- [async-service-3] c.b.t.service.impl.AsyncServiceImpl      : start executeAsync

注意这一行日志：2. do submit,taskCount [101], completedTaskCount [87], activeCount [5], queueSize [9]

这说明提交任务到线程池的时候，调用的是submit(Callable task)这个方法，当前已经提交了101个任务，完成了87个，当前有5个线程在处理任务，还剩9个任务在队列中等待，线程池的基本情况一路了然；

至此，springboot线程池服务的实战就完成了，希望能帮您在工程中快速实现异步服务；

spring-boot 方法异步调用，自定义线程池配置使用

1、在主类中添加@EnableAsync注解：

@SpringBootApplication
@EnableScheduling
@EnableAsync
public class MySpringBootApplication {
	private static Logger logger = LoggerFactory.getLogger(MySpringBootApplication.class);
	
	public static void main(String[] args) {
		SpringApplication.run(MySpringBootApplication.class, args);
		logger.info("My Spring Boot Application Started");
	}

2、创建一个AsyncTask类，在里面添加两个用@Async注解的task：

@Component
public class AsyncTask {
	protected final Logger logger = LoggerFactory.getLogger(this.getClass());
	
	@Async
	public Future<String> doTask1() throws InterruptedException{
		logger.info("Task1 started.");
		long start = System.currentTimeMillis();
        Thread.sleep(5000);
        long end = System.currentTimeMillis();
        
        logger.info("Task1 finished, time elapsed: {} ms.", end-start);
        
        return new AsyncResult<>("Task1 accomplished!");
	}
	
	@Async
	public Future<String> doTask2() throws InterruptedException{
		logger.info("Task2 started.");
		long start = System.currentTimeMillis();
        Thread.sleep(3000);
        long end = System.currentTimeMillis();
        
        logger.info("Task2 finished, time elapsed: {} ms.", end-start);
        
        return new AsyncResult<>("Task2 accomplished!");
	}
}

3、万事俱备，开始测试：


public class TaskTests extends BasicUtClass{
	@Autowired
	private AsyncTask asyncTask;
	
	
	@Test
	public void AsyncTaskTest() throws InterruptedException, ExecutionException {
		Future<String> task1 = asyncTask.doTask1();
		Future<String> task2 = asyncTask.doTask2();
		
		while(true) {
			if(task1.isDone() && task2.isDone()) {
				logger.info("Task1 result: {}", task1.get());
				logger.info("Task2 result: {}", task2.get());
				break;
			}
			Thread.sleep(1000);
		}
		
		logger.info("All tasks finished.");
	}
}

测试结果：

2016-12-13 11:12:24,850:INFO main (AsyncExecutionAspectSupport.java:245) - No TaskExecutor bean found for async processing
2016-12-13 11:12:24,864:INFO SimpleAsyncTaskExecutor-1 (AsyncTask.java:22) - Task1 started.
2016-12-13 11:12:24,865:INFO SimpleAsyncTaskExecutor-2 (AsyncTask.java:34) - Task2 started.
2016-12-13 11:12:27,869:INFO SimpleAsyncTaskExecutor-2 (AsyncTask.java:39) - Task2 finished, time elapsed: 3001 ms.
2016-12-13 11:12:29,866:INFO SimpleAsyncTaskExecutor-1 (AsyncTask.java:27) - Task1 finished, time elapsed: 5001 ms.
2016-12-13 11:12:30,853:INFO main (TaskTests.java:23) - Task1 result: Task1 accomplished!
2016-12-13 11:12:30,853:INFO main (TaskTests.java:24) - Task2 result: Task2 accomplished!
2016-12-13 11:12:30,854:INFO main (TaskTests.java:30) - All tasks finished.

可以看到，没有自定义的Executor，所以使用缺省的TaskExecutor 。

前面是最简单的使用方法。如果想使用自定义的Executor，可以按照如下几步来：

1、新建一个Executor配置类，顺便把@EnableAsync注解搬到这里来：

@Configuration
@EnableAsync
public class ExecutorConfig {

	/** Set the ThreadPoolExecutor's core pool size. */
	private int corePoolSize = 10;
	/** Set the ThreadPoolExecutor's maximum pool size. */
	private int maxPoolSize = 200;
	/** Set the capacity for the ThreadPoolExecutor's BlockingQueue. */
	private int queueCapacity = 10;

	@Bean
	public Executor mySimpleAsync() {
		ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();
		executor.setCorePoolSize(corePoolSize);
		executor.setMaxPoolSize(maxPoolSize);
		executor.setQueueCapacity(queueCapacity);
		executor.setThreadNamePrefix("MySimpleExecutor-");
		executor.initialize();
		return executor;
	}
	
	@Bean
	public Executor myAsync() {
		ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();
		executor.setCorePoolSize(corePoolSize);
		executor.setMaxPoolSize(maxPoolSize);
		executor.setQueueCapacity(queueCapacity);
		executor.setThreadNamePrefix("MyExecutor-");

		// 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());
		executor.initialize();
		return executor;
	}
}

这里定义了两个不同的Executor，第二个重新设置了pool已经达到max size时候的处理方法；同时指定了线程名字的前缀。

2、自定义Executor的使用：

@Component
public class AsyncTask {
	protected final Logger logger = LoggerFactory.getLogger(this.getClass());
	
	@Async("mySimpleAsync")
	public Future<String> doTask1() throws InterruptedException{
		logger.info("Task1 started.");
		long start = System.currentTimeMillis();
        Thread.sleep(5000);
        long end = System.currentTimeMillis();
        
        logger.info("Task1 finished, time elapsed: {} ms.", end-start);
        
        return new AsyncResult<>("Task1 accomplished!");
	}
	
	@Async("myAsync")
	public Future<String> doTask2() throws InterruptedException{
		logger.info("Task2 started.");
		long start = System.currentTimeMillis();
        Thread.sleep(3000);
        long end = System.currentTimeMillis();
        
        logger.info("Task2 finished, time elapsed: {} ms.", end-start);
        
        return new AsyncResult<>("Task2 accomplished!");
	}
}

就是把上面自定义Executor的类名，放进@Async注解中。

3、（测试用例不变）测试结果：

2016-12-13 10:57:11,998:INFO MySimpleExecutor-1 (AsyncTask.java:22) - Task1 started.
2016-12-13 10:57:12,001:INFO MyExecutor-1 (AsyncTask.java:34) - Task2 started.
2016-12-13 10:57:15,007:INFO MyExecutor-1 (AsyncTask.java:39) - Task2 finished, time elapsed: 3000 ms.
2016-12-13 10:57:16,999:INFO MySimpleExecutor-1 (AsyncTask.java:27) - Task1 finished, time elapsed: 5001 ms.
2016-12-13 10:57:17,994:INFO main (TaskTests.java:23) - Task1 result: Task1 accomplished!
2016-12-13 10:57:17,994:INFO main (TaskTests.java:24) - Task2 result: Task2 accomplished!
2016-12-13 10:57:17,994:INFO main (TaskTests.java:30) - All tasks finished.
2016-12-13 10:57:18,064 Thread-3 WARN Unable to register Log4j shutdown hook because JVM is shutting down. Using SimpleLogger

可见，线程名字的前缀变了，两个task使用了不同的线程池了。

参考博客：http://blog.youkuaiyun.com/clementad/article/details/53607311

作者：BosyJ
轉載：https://www.cnblogs.com/pejsidney/
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