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.csdn.net/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：
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;
}- 1
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；
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.csdn.net/clementad/article/details/53607311