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1.直接看代码中的demo:

package com.landon.mavs.example.concurrent;

import java.util.concurrent.Callable;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;

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

/**
 * 
 * 使用guava实现异步回调 {@link java.util.concurrent.Future}
 * {@link com.google.common.util.concurrent.ListenableFuture}
 * {@link com.google.common.util.concurrent.FutureCallback}
 * 
 * @author landon
 * 
 
*/

public class FutureCallbackExample {
    
public static void main(String[] args) throws Exception {
        
// 原生的Future模式,实现异步
        ExecutorService nativeExecutor = Executors.newSingleThreadExecutor();
        Future<String> nativeFuture = nativeExecutor
                .submit(new Callable<String>() {

                    @Override
                    
public String call() throws Exception {
                        
// 使用sleep模拟调用耗时
                        TimeUnit.SECONDS.sleep(1);
                        
return "This is native future call.not support async callback";
                    }

                }
);

        
// Future只实现了异步,而没有实现回调.所以此时主线程get结果时阻塞.或者可以轮训以便获取异步调用是否完成
        System.out.println(nativeFuture.get());

        
// 好的实现应该是提供回调,即异步调用完成后,可以直接回调.本例采用guava提供的异步回调接口,方便很多.
        ListeningExecutorService guavaExecutor = MoreExecutors
                .listeningDecorator(Executors.newSingleThreadExecutor());
        
final ListenableFuture<String> listenableFuture = guavaExecutor
                .submit(new Callable<String>() {

                    @Override
                    
public String call() throws Exception {
                        Thread.sleep(1000);
                        
return "this is guava future call.support async callback";
                    }

                }
);

        
// 注册监听器,即异步调用完成时会在指定的线程池中执行注册的监听器
        listenableFuture.addListener(new Runnable() {

            @Override
            
public void run() {
                
try {
                    System.out.println("async complete.result:"
                            
+ listenableFuture.get());
                }
 catch (Exception e) {
                }

            }

        }
, Executors.newSingleThreadExecutor());

        
// 主线程可以继续执行,异步完成后会执行注册的监听器任务.
        System.out.println("go on execute.asyn complete will callback");

        
// 除了ListenableFuture,guava还提供了FutureCallback接口,相对来说更加方便一些.
        ListeningExecutorService guavaExecutor2 = MoreExecutors
                .listeningDecorator(Executors.newSingleThreadExecutor());
        
final ListenableFuture<String> listenableFuture2 = guavaExecutor2
                .submit(new Callable<String>() {

                    @Override
                    
public String call() throws Exception {
                        Thread.sleep(1000);
                        System.out.println("asyncThreadName:"
                                
+ Thread.currentThread().getName());
                        
return "this is guava future call.support async callback using FutureCallback";
                    }

                }
);
        
// 注意这里没用指定执行回调的线程池,从输出可以看出,默认是和执行异步操作的线程是同一个.
        Futures.addCallback(listenableFuture2, new FutureCallback<String>() {

            @Override
            
public void onSuccess(String result) {
                System.out
                        .println("async callback(using FutureCallback) result:"
                                
+ result);
                System.out.println("execute callback threadName:"
                        
+ Thre            }ad.currentThread().getName());


            @Override
            
public void onFailure(Throwable t) {
            }

        }
);
    }

}



2.总结:利用guava的ListenableFuture和FutureCallback方便的实现异步回调.
posted on 2014-02-27 14:54 landon 阅读(5867) 评论(3)  编辑  收藏 所属分类: Program

FeedBack:
# re: 使用guava实现异步回调
2014-02-28 10:09 | 魏五锁业
谢谢博主分享 啊  回复  更多评论
  
# re: 使用guava实现异步回调
2014-03-01 08:14 | 魏五锁业
看不明白啊博主  回复  更多评论
  
# re: 使用guava实现异步回调
2014-03-05 16:37 | 百家乐讯特
学习了··谢谢!  回复  更多评论
  

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