ThreadLocal与InheritableThreadLocal

ThreadLocal底层是个map每次set值的时候把当前线程与值放到里面
    ThreadLocal.ThreadLocalMap threadLocals = null;

　　

 

 

 

 

 

这种结构在大数据量并发请求时会，会产生内存泄漏。
请求时set进去，正常退出move掉，来不及remove的数据会停留在内存中，外界还有引用，gc不会收就会泄露

　　如果子线程需要使用父级的数据去处理任务，然后回到父线程归纳处理，这时候ThreadLocal就不满足了

    private static ThreadLocal<String> inheritableThreadLocal = new ThreadLocal<>();

    public static void main(String[] args) throws IOException {

        inheritableThreadLocal.set("Value from parent thread");
        // 创建线程池
        ExecutorService executorService = Executors.newFixedThreadPool(5);
        // 提交任务（创建子线程）
        for (int i = 0; i < 5; i++) {
            executorService.submit(
                    () -> {
                        try {
                            // 子线程中获取从父线程继承的值
                            String value = (String) inheritableThreadLocal.get();
                            System.out.println("Value in child thread: " + value);
                        } finally {
                            // 任务执行完毕后清除值
                            inheritableThreadLocal.remove();
                        }
                    });
        }
        // 关闭线程池
        executorService.shutdown();
    }

　　这时候子线程获取父级线程的数据就是空

 

InheritableThreadLocal是ThreadLocal子类，其区别

　　

    private static InheritableThreadLocal<String> inheritableThreadLocal = new InheritableThreadLocal<>();

    public static void main(String[] args) throws IOException {

        inheritableThreadLocal.set("Value from parent thread");
        // 创建线程池
        ExecutorService executorService = Executors.newFixedThreadPool(5);
        // 提交任务（创建子线程）
        for (int i = 0; i < 5; i++) {
            executorService.submit(
                    () -> {
                        try {
                            // 子线程中获取从父线程继承的值
                            String value = (String) inheritableThreadLocal.get();
                            System.out.println("Value in child thread: " + value);
                        } finally {
                            // 任务执行完毕后清除值
                            inheritableThreadLocal.remove();
                        }
                    });
        }
        // 关闭线程池
        executorService.shutdown();
    }

　　

 

inheritableThreadLocal.set("Value from parent thread");设置值时

 

 

 

 

 

把父级的inheritableThreadLocals复制给子集的inheritableThreadLocals，

  效果如下