Spring Boot使用ThreadLocal、Inherit

4. 异步情况下使用线程池 InheritableThreadLocal的表现

在异步时InheritableThreadLocal没有发现异常，现在我们加上线程池，看看最终效果。
1）增加线程池
为了尽快看到效果，我们将线程的核心数和最大数都设置为2。

@Configuration
//@EnableAsync//开启注解：开启异步支持
public class ThreadPool {

    private static final int CORE_POOL_SIZE = Runtime.getRuntime().availableProcessors() *2;
    private static final int MAX_POOL_SIZE = CORE_POOL_SIZE *4 <256 ? 256 : CORE_POOL_SIZE * 4;
    private static final int KEEP_ALIVE_TIME = 10; //允许线程空闲时间（单位为秒）
    private static final int QUEUE_CAPACITY = 200; // 缓冲队列数
    private static final int AWAIT_TERMINATION = 60;//线程池中任务的等待时间，如果超过这个时候还没有销毁就强制销毁
    private static final Boolean WAIT_FOR_TASKS_TO_COMPLETE_ON_SHUTDOWN = true;//用来设置线程池关闭的时候等待所有任务都完成再继续销毁其他的Bean
    private static final String THREAD_NAME_PREFIX = "PiceaAsync-Service-"; // 线程池名前缀

    /**
     * <p>"@Bean("piceaTaskExecutor")，Bean后面的（）内容可以省略
     * 如果省略则使用方法名<p>
     * @author jiangbing.yang
     * @date   2019/3/27 11:07
     * @params
     * @return
     * @throws
     */

    @Bean("piceaTaskExecutor")
    public static ThreadPoolTaskExecutorpiceaTaskExecutor () {
        ThreadPoolTaskExecutor taskExecutor = new ThreadPoolTaskExecutor();
        taskExecutor.setCorePoolSize(2);
        taskExecutor.setMaxPoolSize(2);
        taskExecutor.setKeepAliveSeconds(KEEP_ALIVE_TIME);
        taskExecutor.setQueueCapacity(QUEUE_CAPACITY);
        taskExecutor.setThreadNamePrefix(THREAD_NAME_PREFIX);
        taskExecutor.setWaitForTasksToCompleteOnShutdown(WAIT_FOR_TASKS_TO_COMPLETE_ON_SHUTDOWN);
        taskExecutor.setAwaitTerminationSeconds(AWAIT_TERMINATION);
        // 线程池对拒绝任务的处理策略
        taskExecutor.setRejectedExecutionHandler(new ThreadPoolExecutor.CallerRunsPolicy());
        // 初始化
        taskExecutor.initialize();
        return taskExecutor;
    }
}

2）在Service层增加方法
先增加接口

    void testThreadLocalAsyncThreadPool() throws Exception;

然后增加实现

    @Async("piceaTaskExecutor")
    @Override
    public void testThreadLocalAsyncThreadPool() throws Exception {
        System.out.println("我是Service层处理线程，线程名：" + Thread.currentThread().getName());
        System.out.println(" InheritableThreadLocalUtil保存的值为：" + InheritableThreadLocalUtil.getValue());
        InheritableThreadLocalUtil.remove();
    }

3）在Controller层增加测试方法

    @RequestMapping("/testItlTl")
    public String testInheritableThreadLocalThreadPool() throws Exception {
        System.out.println("我是Controller层处理线程，线程名：" + Thread.currentThread().getName());
        InheritableThreadLocalUtil.setValue("我是：testInheritableThreadLocal");
        System.out.println("这里是处理过程，处理中.........");
        System.out.println(" InheritableThreadLocalUtil保存的值为：" + InheritableThreadLocalUtil.getValue());
        piceaService.testThreadLocalAsyncThreadPool();
        return "testInheritableThreadLocalThreadPool:";
    }

4）测试结果
浏览器中输入http://localhost:2001/testItlTl
运行3次，第1次和第2次中发现，可以取到父线程的值，第3次的时间，发现就取不到父线程设置的值。

Spring-boot-TL-ITLTL.png

5. 异步情况下使用线程池 TransmittableThreadLocal 的表现

在异步且使用线程池的情况下，InheritableThreadLocal已经出现问题，现在我们使用TransmittableThreadLocal 看看效果。
1）修改线程池，使用TTL的包装类
为了尽快看到效果，我们将线程的核心数和最大数都设置为2。主要是这一段“ TtlExecutors.getTtlExecutor(taskExecutor);”，这个是重点，这个是重点，这个是重点。重要的问题说三次。

@Configuration
//@EnableAsync//开启注解：开启异步支持
public class ThreadPool {

    private static final int CORE_POOL_SIZE = Runtime.getRuntime().availableProcessors() *2;
    private static final int MAX_POOL_SIZE = CORE_POOL_SIZE *4 <256 ? 256 : CORE_POOL_SIZE * 4;
    private static final int KEEP_ALIVE_TIME = 10; //允许线程空闲时间（单位为秒）
    private static final int QUEUE_CAPACITY = 200; // 缓冲队列数
    private static final int AWAIT_TERMINATION = 60;//线程池中任务的等待时间，如果超过这个时候还没有销毁就强制销毁
    private static final Boolean WAIT_FOR_TASKS_TO_COMPLETE_ON_SHUTDOWN = true;//用来设置线程池关闭的时候等待所有任务都完成再继续销毁其他的Bean
    private static final String THREAD_NAME_PREFIX = "PiceaAsync-Service-"; // 线程池名前缀

    /**
     * <p>"@Bean("piceaTaskExecutor")，Bean后面的（）内容可以省略
     * 如果省略则使用方法名<p>
     * @author jiangbing.yang
     * @date   2019/3/27 11:07
     * @params
     * @return
     * @throws
     */

    @Bean("piceaTaskExecutor")
    public static Executor piceaTaskExecutor () {
        ThreadPoolTaskExecutor taskExecutor = new ThreadPoolTaskExecutor();
        taskExecutor.setCorePoolSize(2);
        taskExecutor.setMaxPoolSize(2);
        taskExecutor.setKeepAliveSeconds(KEEP_ALIVE_TIME);
        taskExecutor.setQueueCapacity(QUEUE_CAPACITY);
        taskExecutor.setThreadNamePrefix(THREAD_NAME_PREFIX);
        taskExecutor.setWaitForTasksToCompleteOnShutdown(WAIT_FOR_TASKS_TO_COMPLETE_ON_SHUTDOWN);
        taskExecutor.setAwaitTerminationSeconds(AWAIT_TERMINATION);
        // 线程池对拒绝任务的处理策略
        taskExecutor.setRejectedExecutionHandler(new ThreadPoolExecutor.CallerRunsPolicy());
        // 初始化
        taskExecutor.initialize();
//        return taskExecutor;
        return TtlExecutors.getTtlExecutor(taskExecutor);
    }
}

2）在Service层增加方法
先增加接口

    void testThreadLocalAsyncThreadPoolTtl() throws Exception;

然后增加实现

    @Async("piceaTaskExecutor")
    @Override
    public void testThreadLocalAsyncThreadPoolTtl() throws Exception {
        System.out.println("我是Service层处理线程，线程名：" + Thread.currentThread().getName());
        System.out.println(" TransmittableThreadLocalUtil：" + TransmittableThreadLocalUtil.getValue());
        TransmittableThreadLocalUtil.remove();
    }

3）在Controller层增加测试方法

    @RequestMapping("/testTtlTl")
    public String testTransmittableThreadLocalThreadPool() throws Exception {
        System.out.println("我是Controller层处理线程，线程名：" + Thread.currentThread().getName());
        TransmittableThreadLocalUtil.setValue("我是：testTransmittableThreadLocalThreadPool");
        System.out.println("这里是处理过程，处理中.........");
        System.out.println(" TransmittableThreadLocalUtil保存的值为：" + TransmittableThreadLocalUtil.getValue());
        piceaService.testThreadLocalAsyncThreadPoolTtl();
        return "testInheritableThreadLocalThreadPool:";
    }

4）测试结果
浏览器中输入http://localhost:2001/testTtlTl
运行3次以上，发现在都可以取到父线程的值。

Spring-boot-TL-TTLTL.png

6. 三个工具类的方法

1）ThreadLocalUtil

public class ThreadLocalUtil {
    public static final ThreadLocal<String> THREAD_LOCAL = new ThreadLocal<>();
    //设置线程需要保存的值
    public static void setValue (String str) {
        THREAD_LOCAL.set(str);
    }
    //获取线程中保存的值
    public static String getValue() {
        return THREAD_LOCAL.get();
    }
    //移除线程中保存的值
    public static void remove() {
        THREAD_LOCAL.remove();
    }
}

2） InheritableThreadLocalUtil

public class InheritableThreadLocalUtil {
    public static final InheritableThreadLocal<String> THREAD_LOCAL = new InheritableThreadLocal<>();
    //设置线程需要保存的值
    public static void setValue (String str) {
        THREAD_LOCAL.set(str);
    }
    //获取线程中保存的值
    public static String getValue() {
        return THREAD_LOCAL.get();
    }
    //移除线程中保存的值
    public static void remove() {
        THREAD_LOCAL.remove();
    }
}

3） TransmittableThreadLocalUtil

public class TransmittableThreadLocalUtil {
    public static final TransmittableThreadLocal<String> THREAD_LOCAL = new TransmittableThreadLocal<>();
    //设置线程需要保存的值
    public static void setValue (String str) {
        THREAD_LOCAL.set(str);
    }
    //获取线程中保存的值
    public static String getValue() {
        return THREAD_LOCAL.get();
    }
    //移除线程中保存的值
    public static void remove() {
        THREAD_LOCAL.remove();
    }
}

第一章节请移步
Spring Boot使用ThreadLocal、InheritableThreadLocal、TransmittableThreadLocal -1

其它注意

本文章样例：
工程名：spring-boot-inheritablethreadlocal
GitHub：https://github.com/zzyjb/SpringBootLearning

关于异步服务和线程池请移步

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