多线程-InheritableThreadLocal

Posted 2020-10-08

InheritableThreadLocal可以在子线程中取得父线程继承下来的值，即可以让子线程从父进程中取得值。

package org.github.lujiango;

public class Test04 {
    static InheritableThreadLocal<String> itl = new InheritableThreadLocal<String>();

    static class ThreadA extends Thread {
        @Override
        public void run() {
            try {
                System.out.println("ThreadA get: " + itl.get());
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }

    public static void main(String[] args) {

        try {
            itl.set("Main");
            Thread.sleep(1000);
            ThreadA a = new ThreadA();
            a.start();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

}

　　InheritableThreadLocal即可以设置默认值，也可以在继承父线程值的同时修改。

package org.github.lujiango;

class InheritableThreadLocalExt extends InheritableThreadLocal<String> {
    @Override
    protected String initialValue() {
        return "defalut";
    }

    @Override
    protected String childValue(String parentValue) {
        return parentValue + " child";
    }
}

public class Test04 {
    static InheritableThreadLocalExt itl = new InheritableThreadLocalExt();

    static class ThreadA extends Thread {
        @Override
        public void run() {
            try {
                Thread.sleep(1000);
                System.out.println("ThreadA get: " + itl.get());
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }

    public static void main(String[] args) {

        try {
            System.out.println(itl.get());
            itl.set("Main1");
            Thread.sleep(1000);
            ThreadA a = new ThreadA();
            a.start();
            itl.set("Main2");
            System.out.println(itl.get());
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

}

注：如果子线程在取得值得同时，主线程将InheritableThreadLocal中的值进行更改，那么子线程取到的值还是旧值。