Springboot線程池服務實戰分享

我們常用ThreadPoolExecutor提供的線程池服務，springboot框架提供了@Async注解，幫助我們更方便的將業務邏輯提交到線程池中異步執行，今天我們就來實戰體驗這個線程池服務；
實戰環境
windowns10；
jdk1.8；
springboot 1.5.9.RELEASE；
開發工具：IntelliJ IDEA；

這里面有多個工程，本次用到的工程為threadpooldemoserver，如下圖紅框所示：
實戰步驟梳理
本次實戰的步驟如下：
創建springboot工程；
創建Service層的接口和實現；
創建controller，開發一個http服務接口，里面會調用service層的服務；
創建線程池的配置；
將Service層的服務異步化，這樣每次調用都會都被提交到線程池異步執行；
擴展ThreadPoolTaskExecutor，在提交任務到線程池的時候可以觀察到當前線程池的情況；
創建springboot工程
用IntelliJ IDEA創建一個springboot的web工程threadpooldemoserver，pom.xml內容如下：

<?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>

創建Service層的接口和實現
創建一個service層的接口AsyncService，如下：

public interface AsyncService {

    /**
     * 執行異步任務
     */
    void executeAsync();
}

對應的AsyncServiceImpl，實現如下：

@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");
    }
}

這個方法做的事情很簡單：sleep了一秒鐘；
創建controller
創建一個controller為Hello，里面定義一個http接口，做的事情是調用Service層的服務，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");

        //調用service層的任務
        asyncService.executeAsync();

        logger.info("end submit");

        return "success";
    }
}

至此，我們已經做好了一個http請求的服務，里面做的事情其實是同步的，接下來我們就開始配置springboot的線程池服務，將service層做的事情都提交到線程池中去處理；
springboot的線程池配置
創建一個配置類ExecutorConfig，用來定義如何創建一個ThreadPoolTaskExecutor，要使用@Configuration和@EnableAsync這兩個注解，表示這是個配置類，并且是線程池的配置類，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();
        //配置核心線程數
        executor.setCorePoolSize(5);
        //配置最大線程數
        executor.setMaxPoolSize(5);
        //配置隊列大小
        executor.setQueueCapacity(99999);
        //配置線程池中的線程的名稱前綴
        executor.setThreadNamePrefix("async-service-");

        // rejection-policy：當pool已經達到max size的時候，如何處理新任務
        // CALLER_RUNS：不在新線程中執行任務，而是有調用者所在的線程來執行
        executor.setRejectedExecutionHandler(new ThreadPoolExecutor.CallerRunsPolicy());
        //執行初始化
        executor.initialize();
        return executor;
    }
}

注意，上面的方法名稱為asyncServiceExecutor，稍后馬上用到；
將Service層的服務異步化
打開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方法進入的線程池是asyncServiceExecutor方法創建的，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");
    }

驗證效果
將這個springboot運行起來（pom.xml所在文件夾下執行mvn spring-boot:run）；
在瀏覽器輸入：http://localhost:8080；
在瀏覽器用F5按鈕快速多刷新幾次；
在springboot的控制臺看見日志如下：

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，我們可以看到controller的執行線程是"nio-8080-exec-8"，這是tomcat的執行線程，而service層的日志顯示線程名為“async-service-1”，顯然已經在我們配置的線程池中執行了，并且每次請求中，controller的起始和結束日志都是連續打印的，表明每次請求都快速響應了，而耗時的操作都留給線程池中的線程去異步執行；
擴展ThreadPoolTaskExecutor
雖然我們已經用上了線程池，但是還不清楚線程池當時的情況，有多少線程在執行，多少在隊列中等待呢？這里我創建了一個ThreadPoolTaskExecutor的子類，在每次提交線程的時候都會將當前線程池的運行狀況打印出來，代碼如下：

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方法中將任務總數、已完成數、活躍線程數，隊列大小都打印出來了，然后Override了父類的execute、submit等方法，在里面調用showThreadPoolInfo方法，這樣每次有任務被提交到線程池的時候，都會將當前線程池的基本情況打印到日志中；
修改ExecutorConfig.java的asyncServiceExecutor方法，將ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor()改為ThreadPoolTaskExecutor executor = new VisiableThreadPoolTaskExecutor()，如下所示：

@Bean
    public Executor asyncServiceExecutor() {
        logger.info("start asyncServiceExecutor");
        //使用VisiableThreadPoolTaskExecutor
        ThreadPoolTaskExecutor executor = new VisiableThreadPoolTaskExecutor();
        //配置核心線程數
        executor.setCorePoolSize(5);
        //配置最大線程數
        executor.setMaxPoolSize(5);
        //配置隊列大小
        executor.setQueueCapacity(99999);
        //配置線程池中的線程的名稱前綴
        executor.setThreadNamePrefix("async-service-");

        // rejection-policy：當pool已經達到max size的時候，如何處理新任務
        // CALLER_RUNS：不在新線程中執行任務，而是有調用者所在的線程來執行
        executor.setRejectedExecutionHandler(new ThreadPoolExecutor.CallerRunsPolicy());
        //執行初始化
        executor.initialize();
        return executor;
    }

再次啟動該工程，再瀏覽器反復刷新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

注意這一行日志：2. do submit,taskCount [101], completedTaskCount [87], activeCount [5], queueSize [9]
這說明提交任務到線程池的時候，調用的是submit(Callable task)這個方法，當前已經提交了101個任務，完成了87個，當前有5個線程在處理任務，還剩9個任務在隊列中等待，線程池的基本情況一路了然；
至此，springboot線程池服務的實戰就完成了，希望能幫您在工程中快速實現異步服務。