多线程 - 一篇带你理解 InheritableThreadLocal 作用

/**
 * @author Lux Sun
 * @date 2021/12/30
 */
public class Cat {

    public Cat(String name) {
        this.name = name;
    }

    private String name;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    @Override
    public String toString() {
        return "Cat{" +
                "name='" + name + '\'' +
                '}';
    }
}

/**
 * 容器上下文
 * @author Lux Sun
 * @date 2021/12/29
 */
public class ContainerContext {

    public ContainerContext(String id, Cat cat) {
        this.id = id;
        this.cat = cat;
    }

    private String id;

    private Cat cat;

    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }

    public Cat getCat() {
        return cat;
    }

    public void setCat(Cat cat) {
        this.cat = cat;
    }

    @Override
    public String toString() {
        return "ContainerContext{" +
                "id='" + id + '\'' +
                ", cat=" + cat +
                '}';
    }
}

/**
 * 容器处理器
 * @author Lux Sun
 * @date 2021/12/29
 */
public class ContainerContextHandler {

    /**
     * 父子线程圈传递 ContainerContext
     */
    private static final InheritableThreadLocal<ContainerContext> INHERITABLE_THREAD_LOCAL = new InheritableThreadLocal<>();


    /*************************** Getter/Setter ***************************/

    public static ContainerContext getContainerContext() {
        return INHERITABLE_THREAD_LOCAL.get();
    }

    public static void setContainerContext(ContainerContext containerContext) {
        INHERITABLE_THREAD_LOCAL.set(containerContext);
    }
}

import lombok.SneakyThrows;
import java.util.concurrent.TimeUnit;

/**
 * @author Lux Sun
 * @date 2021/12/30
 */
public class Test {

    /**
     * 主线程
     * @param args
     */
    public static void main(String[] args) throws InterruptedException {
        // 主线程
        ContainerContext containerContext = new ContainerContext("main", new Cat("main_cat"));
        ContainerContextHandler.setContainerContext(containerContext);

        // 子线程
        new ChildThread().start();
        TimeUnit.MILLISECONDS.sleep(500);

        // 打印主线程信息
        print();
    }

    /**
     * 子线程
     */
    private static class ChildThread extends Thread {
        @SneakyThrows
        @Override
        public void run() {
            // 打印主线程信息
            print();

            ContainerContext containerContext = new ContainerContext("child", new Cat("child_cat"));
            ContainerContextHandler.setContainerContext(containerContext);

            // 打印子线程信息
            print();

            // 孙子线程
            new GrandChildThread().start();
            TimeUnit.MILLISECONDS.sleep(200);

            // 打印子线程信息
            print();
        }
    }

    /**
     * 孙子线程
     */
    private static class GrandChildThread extends Thread {
        @Override
        public void run() {
            // 打印子线程信息
            print();

            ContainerContext containerContext = new ContainerContext("grandchild", new Cat("grandchild_cat"));
            ContainerContextHandler.setContainerContext(containerContext);

            // 打印孙子线程信息
            print();
        }
    }

    /**
     * 打印
     * @param
     */
    private static void print() {
        System.out.println(ContainerContextHandler.getContainerContext());
    }
}

ContainerContext{id='main', cat=Cat{name='main_cat'}}
ContainerContext{id='child', cat=Cat{name='child_cat'}}
ContainerContext{id='child', cat=Cat{name='child_cat'}}
ContainerContext{id='grandchild', cat=Cat{name='grandchild_cat'}}
ContainerContext{id='child', cat=Cat{name='child_cat'}}
ContainerContext{id='main', cat=Cat{name='main_cat'}}