springboot(十九)-线程池的使用

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。

话不多说，编码开始：

1.创建springboot工程

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

<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.fengyuduke.boot</groupId>
  <artifactId>threadpooldemoserver</artifactId>
  <version>0.0.1-SNAPSHOT</version>
  <packaging>jar</packaging>

  <name>threadpooldemoserver</name>
  <url>http://maven.apache.org</url>

   <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-devtools</artifactId>
            <optional>true</optional> <!-- 这个需要为 true 热部署才有效 -->
        </dependency>
        <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>

2.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);

    @Overridepublic 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；

3.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；

4.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；

5.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

  1. 将这个springboot运行起来（pom.xml所在文件夹下执行mvn spring-boot:run）；

  2. 在浏览器输入：http://localhost:8080；

  3. 在浏览器用F5按钮快速多刷新几次；

  4. 在springboot的控制台看见日志如下：

    2019-06-13 16:41:01.026  INFO 12652 --- [nio-8080-exec-1] com.fengyuduke.boot.controller.Hello     : start submit
2019-06-13 16:41:01.027  INFO 12652 --- [nio-8080-exec-1] com.fengyuduke.boot.controller.Hello     : end submit
2019-06-13 16:41:01.027  INFO 12652 --- [async-service-1] c.f.boot.serviceimpl.AsyncServiceImpl    : start executeAsync
2019-06-13 16:41:01.174  INFO 12652 --- [nio-8080-exec-3] com.fengyuduke.boot.controller.Hello     : start submit
2019-06-13 16:41:01.174  INFO 12652 --- [nio-8080-exec-3] com.fengyuduke.boot.controller.Hello     : end submit
2019-06-13 16:41:01.174  INFO 12652 --- [async-service-2] c.f.boot.serviceimpl.AsyncServiceImpl    : start executeAsync
2019-06-13 16:41:01.320  INFO 12652 --- [nio-8080-exec-5] com.fengyuduke.boot.controller.Hello     : start submit
2019-06-13 16:41:01.320  INFO 12652 --- [nio-8080-exec-5] com.fengyuduke.boot.controller.Hello     : end submit
2019-06-13 16:41:01.320  INFO 12652 --- [async-service-3] c.f.boot.serviceimpl.AsyncServiceImpl    : start executeAsync
2019-06-13 16:41:01.583  INFO 12652 --- [nio-8080-exec-7] com.fengyuduke.boot.controller.Hello     : start submit
2019-06-13 16:41:01.583  INFO 12652 --- [nio-8080-exec-7] com.fengyuduke.boot.controller.Hello     : end submit
2019-06-13 16:41:01.583  INFO 12652 --- [async-service-4] c.f.boot.serviceimpl.AsyncServiceImpl    : start executeAsync
2019-06-13 16:41:02.027  INFO 12652 --- [async-service-1] c.f.boot.serviceimpl.AsyncServiceImpl    : end executeAsync
2019-06-13 16:41:02.174  INFO 12652 --- [async-service-2] c.f.boot.serviceimpl.AsyncServiceImpl    : end executeAsync
2019-06-13 16:41:02.343  INFO 12652 --- [async-service-3] c.f.boot.serviceimpl.AsyncServiceImpl    : end executeAsync
2019-06-13 16:41:02.583  INFO 12652 --- [async-service-4] c.f.boot.serviceimpl.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-*"，这是tomcat的执行线程，而service层的日志显示线程名为“async-service-*”，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：

@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();
        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：

2019-06-13 16:46:56.490  INFO 12860 --- [io-8080-exec-10] com.fengyuduke.boot.controller.Hello     : start submit
2019-06-13 16:46:56.491  INFO 12860 --- [io-8080-exec-10] c.f.b.c.VisiableThreadPoolTaskExecutor   : async-service-, 2. do submit,taskCount [4], completedTaskCount [4], activeCount [0], queueSize [0]
2019-06-13 16:46:56.491  INFO 12860 --- [io-8080-exec-10] com.fengyuduke.boot.controller.Hello     : end submit
2019-06-13 16:46:56.491  INFO 12860 --- [async-service-5] c.f.boot.serviceimpl.AsyncServiceImpl    : start executeAsync
2019-06-13 16:46:56.793  INFO 12860 --- [nio-8080-exec-2] com.fengyuduke.boot.controller.Hello     : start submit
2019-06-13 16:46:56.793  INFO 12860 --- [nio-8080-exec-2] c.f.b.c.VisiableThreadPoolTaskExecutor   : async-service-, 2. do submit,taskCount [5], completedTaskCount [4], activeCount [1], queueSize [0]
2019-06-13 16:46:56.793  INFO 12860 --- [nio-8080-exec-2] com.fengyuduke.boot.controller.Hello     : end submit
2019-06-13 16:46:56.794  INFO 12860 --- [async-service-1] c.f.boot.serviceimpl.AsyncServiceImpl    : start executeAsync
2019-06-13 16:46:56.935  INFO 12860 --- [nio-8080-exec-4] com.fengyuduke.boot.controller.Hello     : start submit
2019-06-13 16:46:56.935  INFO 12860 --- [nio-8080-exec-4] c.f.b.c.VisiableThreadPoolTaskExecutor   : async-service-, 2. do submit,taskCount [6], completedTaskCount [4], activeCount [2], queueSize [0]
2019-06-13 16:46:56.935  INFO 12860 --- [nio-8080-exec-4] com.fengyuduke.boot.controller.Hello     : end submit
2019-06-13 16:46:56.935  INFO 12860 --- [async-service-2] c.f.boot.serviceimpl.AsyncServiceImpl    : start executeAsync
2019-06-13 16:46:57.072  INFO 12860 --- [nio-8080-exec-6] com.fengyuduke.boot.controller.Hello     : start submit
2019-06-13 16:46:57.073  INFO 12860 --- [nio-8080-exec-6] c.f.b.c.VisiableThreadPoolTaskExecutor   : async-service-, 2. do submit,taskCount [7], completedTaskCount [4], activeCount [3], queueSize [0]
2019-06-13 16:46:57.073  INFO 12860 --- [nio-8080-exec-6] com.fengyuduke.boot.controller.Hello     : end submit
2019-06-13 16:46:57.073  INFO 12860 --- [async-service-3] c.f.boot.serviceimpl.AsyncServiceImpl    : start executeAsync
2019-06-13 16:46:57.215  INFO 12860 --- [nio-8080-exec-8] com.fengyuduke.boot.controller.Hello     : start submit
2019-06-13 16:46:57.216  INFO 12860 --- [nio-8080-exec-8] c.f.b.c.VisiableThreadPoolTaskExecutor   : async-service-, 2. do submit,taskCount [8], completedTaskCount [4], activeCount [4], queueSize [0]
2019-06-13 16:46:57.216  INFO 12860 --- [nio-8080-exec-8] com.fengyuduke.boot.controller.Hello     : end submit
2019-06-13 16:46:57.216  INFO 12860 --- [async-service-4] c.f.boot.serviceimpl.AsyncServiceImpl    : start executeAsync
2019-06-13 16:46:57.345  INFO 12860 --- [io-8080-exec-10] com.fengyuduke.boot.controller.Hello     : start submit
2019-06-13 16:46:57.345  INFO 12860 --- [io-8080-exec-10] c.f.b.c.VisiableThreadPoolTaskExecutor   : async-service-, 2. do submit,taskCount [9], completedTaskCount [4], activeCount [5], queueSize [0]
2019-06-13 16:46:57.345  INFO 12860 --- [io-8080-exec-10] com.fengyuduke.boot.controller.Hello     : end submit
2019-06-13 16:46:57.491  INFO 12860 --- [async-service-5] c.f.boot.serviceimpl.AsyncServiceImpl    : end executeAsync
2019-06-13 16:46:57.491  INFO 12860 --- [async-service-5] c.f.boot.serviceimpl.AsyncServiceImpl    : start executeAsync
2019-06-13 16:46:57.795  INFO 12860 --- [async-service-1] c.f.boot.serviceimpl.AsyncServiceImpl    : end executeAsync
2019-06-13 16:46:57.936  INFO 12860 --- [async-service-2] c.f.boot.serviceimpl.AsyncServiceImpl    : end executeAsync
2019-06-13 16:46:58.074  INFO 12860 --- [async-service-3] c.f.boot.serviceimpl.AsyncServiceImpl    : end executeAsync
2019-06-13 16:46:58.222  INFO 12860 --- [async-service-4] c.f.boot.serviceimpl.AsyncServiceImpl    : end executeAsync
2019-06-13 16:46:58.492  INFO 12860 --- [async-service-5] c.f.boot.serviceimpl.AsyncServiceImpl    : end executeAsync

注意这一行日志：

2. do submit,taskCount [9], completedTaskCount [4], activeCount [5], queueSize [0]

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9个任务，完成了4个，当前有5个线程在处理任务，还剩0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。

代码下载地址：https://gitee.com/fengyuduke/my_open_resources/blob/master/threadpooldemoserver.zip

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原文地址：https://www.cnblogs.com/fengyuduke/p/11017606.html