ListenableFuture根据结果,主动中断流程 -Java

ListenableFuture的说明

Guava 定义了 ListenableFuture接口并继承了JDK concurrent包下的Future接口,ListenableFuture 允许你注册回调方法(callbacks),在运算(多线程执行)完成的时候进行调用, 或者在运算(多线程执行)完成后立即执行。这样简单的改进,使得可以明显的支持更多的操作,这样的功能在JDK concurrent中的Future是不支持的。 在高并发并且需要大量Future对象的情况下,推荐尽量使用ListenableFuture来代替..

ListenableFuture 中的基础方法是addListener(Runnable, Executor), 该方法会在多线程运算完的时候,在Executor中执行指定的Runnable。

不做过多入门介绍,直接上例子。

主动中断例子

maven引入

<dependency>
  <groupId>com.google.guava</groupId>
  <artifactId>guava</artifactId>
  <version>24.1-jre</version>
</dependency>

引入的包:

import com.google.common.util.concurrent.ListenableFuture;
import com.google.common.util.concurrent.ListeningExecutorService;
import com.google.common.util.concurrent.MoreExecutors;

import java.util.Queue;
import java.util.concurrent.*;

main方法:

public static void main(String[] args) {
    ExecutorService executor = Executors.newFixedThreadPool(2);
    ListeningExecutorService listeningExecutorService = MoreExecutors.listeningDecorator(executor);
    final Queue<ListenableFuture<Boolean>> currentMiningTasks = new ConcurrentLinkedQueue<>();
    currentMiningTasks.add(listeningExecutorService.submit(new A()));
    currentMiningTasks.add(listeningExecutorService.submit(new A()));
    currentMiningTasks.add(listeningExecutorService.submit(new A(true)));
    currentMiningTasks.add(listeningExecutorService.submit(new A()));
    currentMiningTasks.add(listeningExecutorService.submit(new A()));
    currentMiningTasks.add(listeningExecutorService.submit(new A()));
    currentMiningTasks.add(listeningExecutorService.submit(new A()));
    currentMiningTasks.add(listeningExecutorService.submit(new A()));
    currentMiningTasks.add(listeningExecutorService.submit(new A()));
    currentMiningTasks.add(listeningExecutorService.submit(new A()));
    currentMiningTasks.add(listeningExecutorService.submit(new A()));
    currentMiningTasks.add(listeningExecutorService.submit(new A()));
    currentMiningTasks.add(listeningExecutorService.submit(new A()));
    currentMiningTasks.add(listeningExecutorService.submit(new A()));
    currentMiningTasks.add(listeningExecutorService.submit(new A()));
    currentMiningTasks.add(listeningExecutorService.submit(new A()));
    currentMiningTasks.add(listeningExecutorService.submit(new A()));
    currentMiningTasks.add(listeningExecutorService.submit(new A()));
    currentMiningTasks.add(listeningExecutorService.submit(new A()));

    // 一定要调用这个方法,isTerminated()永远不为true
    listeningExecutorService.shutdown();
    executor.shutdown();

    for (final ListenableFuture<Boolean> task : currentMiningTasks) {
        try {
            System.out.println("结果..." + task.get());
            if (task.get()) {  // 如果是true,则取消其他任务
                for (final ListenableFuture<Boolean> t : currentMiningTasks) {
                    if (t != null && !t.isCancelled()) {
                        t.cancel(true);
                    }
                }
            }
        } catch (InterruptedException | CancellationException e) {
        } catch (Exception e) {
        }
    }

    while (true) {
        if (listeningExecutorService.isTerminated() && executor.isTerminated()) {
            System.out.println("listeningExecutorService executor结束");
            break;
        }
    }

    System.out.println("结束......");
}

static class A implements Callable {
    Boolean flag = false;

    public A() {
    }

    public A(Boolean flag) {
        this.flag = flag;
    }

    @Override
    public Object call() throws Exception {
        Thread.sleep(1000);
        return flag;
    }
}

运行结果:

结果...false
结果...false
结果...true
结果...false
listeningExecutorService executor结束
结束......

可以看到,收到true的结果,其他的任务没有执行就结束了







发表于: 11天前   最后更新时间: 9天前   游览量:53
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