springboot线程池的使用和扩展

迈不过友情╰ 2023-07-05 10:03 14阅读 0赞

转自：[https://blog.csdn.net/boling\_cavalry/article/details/79120268][https_blog.csdn.net_boling_cavalry_article_details_79120268]

### 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 ###

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][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：

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；

[https_blog.csdn.net_boling_cavalry_article_details_79120268]: https://blog.csdn.net/boling_cavalry/article/details/79120268
[http_localhost_8080]: http://localhost:8080