如何将异步HTTP请求响应组合到一个？

问题描述：

我试图使x请求数量异步。我看了问题Asynchronous IO in Java?和How do you create an asynchronous HTTP request in JAVA?。我发现好的图书馆Asynchronous Http and WebSocket Client library for Java，但我不明白我如何可以安全地将多个结果合并成一个结果。例如，如果我有下面的代码：如何将异步HTTP请求响应组合到一个？

AsyncHttpClient c = new AsyncHttpClient(); 
List<String> urls = getUrls(); 
List<MyResultObject> results = new ArrayList<>(); 
for(String url : urls) 
{ 
    // Create asynchronous request 
    Future<MyResultObject> f = c.prepareGet(url).execute(handler); 

    // How can I add completed responses to my results list ??? 
}

我怎样才能安全地这些结果组合成列表，并在所有的请求都完成继续。

答

我找到了使用期货的this tutorial。您可以执行以下操作：

AsyncHttpClient c = new AsyncHttpClient(); 
List<String> urls = getUrls(); 
List<Future<MyResultObject>> futures = new ArrayList<>(); // keep track of your futures 
List<MyResultObject> results = new ArrayList<>(); 
for(String url : urls) 
{ 
    // Create asynchronous request 
    Future<MyResultObject> f = c.prepareGet(url).execute(handler); 
    futures.add(f); 
} 

// Now retrieve the result 
for (Future<MyResultObject> future : futures) { 
    try { 
    results.add(future.get()); 
    } catch (InterruptedException e) { 
    e.printStackTrace(); 
    } catch (ExecutionException e) { 
    e.printStackTrace(); 
    } 
} 
// continue with your result list

答

你可以调用Future类的get()方法来获得结果。请注意，对该方法的调用可能会阻止，直到结果可用

答

如果要合并几个http请求并获取所有结果。你可以看看代码打击。

package ParallelTasks; 

import org.apache.commons.lang3.tuple.MutablePair; 
import org.apache.commons.lang3.tuple.Pair; 

import java.util.ArrayList; 
import java.util.List; 
import java.util.concurrent.*; 

public class ParallelHttpRequest { 
    //thread pool to execute http request task. 
    static final ExecutorService businessRequestExecutor = Executors.newCachedThreadPool(); 


    public static void main(String[] args) throws InterruptedException, ExecutionException { 
     List<String> urlList = new ArrayList<String>(); 

     final CountDownLatch latch = new CountDownLatch(urlList.size()); 

     List<Future<Pair<String, String>>> list = new ArrayList<Future<Pair<String, String>>>(); 
     for (final String url : urlList) { 
      Future<Pair<String, String>> future = businessRequestExecutor.submit(new Callable<Pair<String, String>>() { 
       public Pair<String, String> call() throws Exception { 
        try { 
         //do post or get http request here. 
         //SoaHttpUtil.post(config.getUrl(), buReqJson); 

         String result = ""; 

         return new MutablePair<String, String>(url, result); 
        } catch (Exception ex) { 
         System.out.println(ex); 
         return new MutablePair<String, String>(url, null); 
        } finally { 
         latch.countDown(); 
        } 
       } 
      }); 
      list.add(future); 
     } 

     //wait no more than 5 seconds. 
     latch.await(5000, TimeUnit.MILLISECONDS); 

     //print finished request's result. 
     for (Future<Pair<String, String>> future : list) { 
      if (future.isDone()) { 
       System.out.println(future.get().getValue()); 
      } 
     } 
    } 
}

如何将异步HTTP请求响应组合到一个？

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