0总述

TransmittableThreadLocal：支持多线程，支持线程池（需要严格执行要素：线程池配置+线程池方法使用完remove（不remove线程池的线程就会有残留）+工具类new TransmittableThreadLocal）

1依赖

        <!-- https://mvnrepository.com/artifact/com.alibaba/transmittable-thread-local -->
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>transmittable-thread-local</artifactId>
            <version>2.14.3</version>
        </dependency>

2线程池

@Bean(name = "pool1")
    public Executor createExecutor1(){
        ThreadPoolTaskExecutor threadPoolTaskExecutor = new ThreadPoolTaskExecutor();
        threadPoolTaskExecutor.setCorePoolSize(2);//核心线程数（默认线程数）
        threadPoolTaskExecutor.setMaxPoolSize(2);//最大线程数
        threadPoolTaskExecutor.setKeepAliveSeconds(60);//允许线程空闲时间（单位：默认为秒）
        threadPoolTaskExecutor.setQueueCapacity(200);//缓冲队列数
        threadPoolTaskExecutor.setThreadNamePrefix("Thread-0");//线程池名前缀
        //线程池对拒绝任务的处理策略
        threadPoolTaskExecutor.setRejectedExecutionHandler(new ThreadPoolExecutor.AbortPolicy());
        threadPoolTaskExecutor.initialize();
        return TtlExecutors.getTtlExecutor(threadPoolTaskExecutor);
    }

要素：

(1) 返回类型Executor

(2) threadPoolTaskExecutor需要通过TTL进行包装TtlExecutors.getTtlExecutor(threadPoolTaskExecutor)

3工具类

public class TransmittableThreadLocalUtil {
    private static ThreadLocal<String> threadLocal = new TransmittableThreadLocal<String>();
    public static void set(String str){
        threadLocal.set(str);
    }
    public static String get(){
        return threadLocal.get();
    }
    public static void remove(){
        threadLocal.remove();
    }
}

要素：new TransmittableThreadLocal<String>()，可用ThreadLocal<String>承接。

4业务调用

Controller

@RequestMapping(method = {RequestMethod.GET}, path = {"/testMultiThread1"})
    public String multiThread1() throws InterruptedException {
        log.info("                                 ");
        log.info("                                 ");
        log.info("MultiThread1Controller,{},{}", Thread.currentThread().getName(), Thread.currentThread().getId(), LocalDateTime.now().toLocalTime());
        ThreadLocalUtil.set("testInfo");
        log.info("MultiThread1ThreadLocal,{}", ThreadLocalUtil.get());
        TransmittableThreadLocalUtil.set("testInfo2");
        log.info("MultiThread1TransmittableThreadLocal,{}", TransmittableThreadLocalUtil.get());
        log.info("--------------------");
        for (int i = 0; i <= 0; i++) {
            mutiThreadService.multiThread1();
        }        
        return "success";
    }

Service

@Async("pool1")
    public void multiThread1() throws InterruptedException {
        log.info("*********************");
        log.info("MutiThreadService,{},{}",Thread.currentThread().getName(),Thread.currentThread().getId(),LocalDateTime.now().toLocalTime());
        log.info("MultiThread1ThreadLocal,{}", ThreadLocalUtil.get());
        log.info("MultiThread1ServiceTransmittableThreadLocal,{}",TransmittableThreadLocalUtil.get());
        log.info("*********************");
        TransmittableThreadLocalUtil.remove();
    }

要素：TransmittableThreadLocalUtil.remove()一定要，经过测试放到Controller和Service都是可以的，放在Service可读性更好，因为Service是线程池，线程池的线程不会销毁继续复用的。

备注：可以模拟去掉TransmittableThreadLocalUtil.remove()进行测试：

比如线程核心数和最大数设置为2，会发现前两次请求是按照预期的，第三次如果是其他入口的Controller访问到相同线程池变量会出现访问到前两次不同入口Controller的线程变量残留。