多线程Future设计模式

Future设计模式核心思想是实现业务逻辑从串行化执行到异步和异步回调

示例一：

package com.dwz.concurrency2.chapter10;

public class SyncInvoker {
    public static void main(String[] args) throws InterruptedException {
        String result = get();
        System.out.println(result);
　　　　 System.out.println("I am done.");
    }
    
    private static String get() throws InterruptedException {
        Thread.sleep(10_000L);
        return "FINISH";
    }
}

测试结果：必须等待 result 获取到才执行 I am done.

优化一：实际的业务被提前调用执行，当我们需要的时候再主动通过 get() 获取返回的数据

Future接口

package com.dwz.concurrency2.chapter9;

public interface Future<T> {
    
    T get() throws InterruptedException;
}

FutureTask接口

package com.dwz.concurrency2.chapter9;

public interface FutureTask<T> {
    
    T call();
}

FutureService类

package com.dwz.concurrency2.chapter9;

import java.util.function.Consumer;

public class FutureService {
    
    public <T> Future<T> submit(final FutureTask<T> task) {
        AsynFuture<T> asynfuture = new AsynFuture<T>();
        new Thread(() -> {
            T result = task.call();
            asynfuture.done(result);
        }).start();
        return asynfuture;
    }
}

AsynFuture是Future的实现类

package com.dwz.concurrency2.chapter9;

public class AsynFuture<T> implements Future<T> {
    private volatile boolean done = false;
    
    private T result;
    
    public void done(T result) {
        synchronized (this) {
            this.result = result;
            this.done = true;
            this.notifyAll();
        }
    }
    
    @Override
    public T get() throws InterruptedException {
        synchronized (this) {
            while (!done) {
                this.wait();
            }
        }
        return result;
    }
    
}

测试类

package com.dwz.concurrency2.chapter10;

public class SyncInvoker {
    public static void main(String[] args) throws InterruptedException {
        FutureService futureservice = new FutureService();
        Future<String> future = futureservice.submit(()->{
　　　　　　　//具体业务
            try {
                Thread.sleep(10_000L);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            return "FINISH";
        });
        
        System.out.println("======================");
        System.out.println(" do other things.");
        System.out.println("***********************");
        System.out.println(future.get());
        System.out.println("I am done.");
    }
}

测试结果： 首先调用futureservice.submit 来处理业务，当我们需要业务处理完成的返回值的时候调用 future.get() 获取，满足设想

优化二：增加callBack回调，处理完成后的数据不需要我们主动去调用，自己返回

修改FutureService类，增加消费者回调

public <T> Future<T> submit(final FutureTask<T> task, final Consumer<T> consumer) {
        AsynFuture<T> asynfuture = new AsynFuture<T>();
        new Thread(() -> {
            T result = task.call();
            asynfuture.done(result);
            consumer.accept(result);
        }).start();
        return asynfuture;
    }

或

public <T> void submit(final FutureTask<T> task, final Consumer<T> consumer) {
        AsynFuture<T> asynfuture = new AsynFuture<T>();
        new Thread(() -> {
            T result = task.call();
            asynfuture.done(result);
            consumer.accept(result);
        }).start();
    }

测试

package com.dwz.concurrency2.chapter9;
/**
 * Future        ->代表的是未来的一个凭据
 * FutureTask    ->将你的调用逻辑进行了隔离
 * FutureService->桥接 Future 和 FutureTask
 */
public class SyncInvoker {
    public static void main(String[] args) throws InterruptedException {
        FutureService futureservice = new FutureService();
        futureservice.submit(() -> {
            //具体业务
            try {
                Thread.sleep(10_000L);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            return "FINISH";
        }, System.out::println);
        
        System.out.println("===================");
        System.out.println(" do other things.");
        Thread.sleep(2000L);
        System.out.println("**********************");
        System.out.println("syncinvoker is done.");
    }
}

测试结果：满足需求

参考视频：https://www.bilibili.com/video/av51503134?p=60