异步回调

异步回调

2019-08-14

目录

1 回调
2 使用wait和notify方法实现异步回调
3 使用CountDownLatch实现异步回调

 

1 回调

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 返回

回调的思想是：

• 类A的a()方法调用类B的b()方法
• 类B的b()方法执行完毕主动调用类A的callback()方法

 

2 使用wait和notify方法实现异步回调

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 返回

ICallback代码：

public interface ICallback {
    void callback(long response);
}

AsyncCallee代码：

import java.util.Random;

public class AsyncCallee {
    private Random random = new Random(System.currentTimeMillis());

    public void doSomething(ICallback iCallback){
        new Thread(()->{
            long res = random.nextInt(4);

            try {
                Thread.sleep(res*1000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }

            iCallback.callback(res);
        }).start();
    }
}

Caller1代码：

public class Caller1 implements ICallback{
    private final Object lock = new Object();
    AsyncCallee callee;
    public Caller1(AsyncCallee asyncCallee){
        callee=asyncCallee;
    }

    public void callback(long response) {
        System.out.println("得到结果");
        System.out.println(response);
        System.out.println("调用结束");

        synchronized (lock) {
            lock.notifyAll();
        }
    }

    public void call(){
        System.out.println("发起调用");
        callee.doSomething(this);
        System.out.println("调用返回");
    }

    public static void main(String[] args) {
        AsyncCallee asyncCallee=new AsyncCallee();
        Caller1 demo1 = new Caller1(asyncCallee);
        demo1.call();

        synchronized (demo1.lock){
            try {
                demo1.lock.wait();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }

        System.out.println("主线程内容");
    }
}

3 使用CountDownLatch实现异步回调

---

 返回

import java.util.concurrent.CountDownLatch;

public class Caller2 implements ICallback{
    private final CountDownLatch countDownLatch = new CountDownLatch(1);
    AsyncCallee callee;
    public Caller2(AsyncCallee asyncCallee){
        callee=asyncCallee;
    }

    @Override
    public void callback(long response) {
        System.out.println("得到结果");
        System.out.println(response);
        System.out.println("调用结束");

        countDownLatch.countDown();
    }

    public void call(){
        System.out.println("发起调用");
        callee.doSomething(this);
        System.out.println("调用返回");
    }


    public static void main(String[] args) {
        AsyncCallee asyncCallee=new AsyncCallee();
        Caller2 demo4 = new Caller2(asyncCallee);
        demo4.call();

        try {
            demo4.countDownLatch.await();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

        System.out.println("主线程内容");
    }
}