image.png

思路

多个并行任务，执行的时候，最后一个任务执行后开始执行 （可以自己实现，建议不要，容易出问题）后面出具 reactor版的方案

参数说明：

size 并行个数
ChildTask<T> childTask 子任务
EndTask<T> endTask 合并结束后执行的任务
int timeout, 超时时间
Executor multiThreadExecutor 子任务执行线程
Executor complateThreadExecutor 任务结束后执行线程
AsyncThreadSwitchListener asyncThreadSwitchListene 线程切换参数

代码部分

  public static <T> void disassemblyTasks(int size, ChildTask<T> childTask, EndTask<T> endTask, int timeout, Executor multiThreadExecutor,Executor complateThreadExecutor, AsyncThreadSwitchListener asyncThreadSwitchListener) {
        asyncThreadSwitchListener.hold();
        CompletableFuture<T>[] completableFutures = new CompletableFuture[size];
        //执行子任务
        for (int i = 0; i < size; i++) {
            int finalI = i;
            completableFutures[i] = new CompletableFuture<>();
            multiThreadExecutor.execute(() -> {
                asyncThreadSwitchListener.cover();
                try {
                    childTask.run(completableFutures[finalI], finalI);
                } finally {
                    asyncThreadSwitchListener.clear();
                }
            });
        }
        CompletableFuture<Void> voidCompletableFuture = CompletableFuture
                .allOf(completableFutures)
                .whenCompleteAsync((unused, throwable) -> {
                    asyncThreadSwitchListener.cover();
                    try {
                        endTask.run(completableFutures, throwable);
                    } finally {
                        asyncThreadSwitchListener.clear();
                    }
                }, complateThreadExecutor);
      //超时控制
        CompletableFutureUtil.within(voidCompletableFuture, timeout, TimeUnit.MILLISECONDS);
    }

/**
 * <h1>同步场景会失效</h1>
 * 线程切换回调函数
 * 线程切换上下文通过这个进行切换
 */
public interface AsyncThreadSwitchListener {

    AsyncThreadSwitchListener ASYNC_THREAD_SWITCH_LISTENR = new AsyncThreadSwitchListener() {
        @Override
        public void hold() {
        }

        @Override
        public void clear() {
        }

        @Override
        public void cover() {
        }
    };


    void hold();

    void clear();

    void cover();


}

import java.util.concurrent.CompletableFuture;

public interface ChildTask<T> {
    /**
     * @description 子任务执行
     * @author xinjiu
     */
    void run(CompletableFuture<T> completableFuture, int number);
}


import java.util.concurrent.CompletableFuture;

public interface EndTask<T> {
//结束任务
    void run(CompletableFuture<T>[] completableFutures, Throwable throwable);
}

import java.util.concurrent.CompletableFuture;
import java.util.concurrent.ScheduledThreadPoolExecutor;
import java.util.concurrent.ThreadFactory;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;
import java.util.function.Function;

/*
 * 通用的异步处理工具 超时工具
 * */
public class CompletableFutureUtil {

    public static <T> void within(CompletableFuture<T> future, long timeout, TimeUnit unit) {
        final CompletableFuture<T> timeoutFuture = timeoutAfter(timeout, unit);
        // 哪个先完成 就apply哪一个结果 这是一个关键的API
        future.applyToEitherAsync(timeoutFuture, Function.identity());
    }

    public static <T> CompletableFuture<T> timeoutAfter(long timeout, TimeUnit unit) {
        CompletableFuture<T> result = new CompletableFuture<>();
        // timeout 时间后 抛出TimeoutException 类似于sentinel / watcher
        Delayer.delayer.schedule(() -> result.completeExceptionally(new TimeoutException("MultiTask timeOut ："+timeout)), timeout, unit);
        return result;
    }

    /**
     * Singleton delay scheduler, used only for starting and * cancelling tasks.
     */
    static final class Delayer {
        static final class DaemonThreadFactory implements ThreadFactory {
            @Override
            public Thread newThread(Runnable r) {
                Thread t = new Thread(r);
                t.setDaemon(true);
                t.setName("CompletableFutureDelayScheduler");
                return t;
            }
        }

        static final ScheduledThreadPoolExecutor delayer;

        // 注意，这里使用一个线程就可以搞定 因为这个线程并不真的执行请求 而是仅仅抛出一个异常
        static {
            (delayer = new ScheduledThreadPoolExecutor(
                    1, new DaemonThreadFactory())).
                    setRemoveOnCancelPolicy(true);
        }
    }
}