如何发送并行的GET请求并等待结果响应？

如何发送并行的GET请求并等待结果响应？

通常，您需要将工作单元封装在

Runnable

或中

java.util.concurrent.Callable

，然后通过

java.util.concurrent.Executor

（或

org.springframework.core.task.TaskExecutor

）执行。这允许每个工作单元分别执行，通常以异步方式执行（取决于的实现

Executor

）。

因此，对于您的特定问题，您可以执行以下 *** 作：

import java.util.ArrayList;import java.util.Iterator;import java.util.List;import java.util.concurrent.Callable;import java.util.concurrent.Executor;import java.util.concurrent.FutureTask;import org.apache.http.client.methods.HttpGet;import org.apache.http.impl.client.BasicResponseHandler;import org.apache.http.impl.client.DefaultHttpClient;import org.springframework.stereotype.Controller;import org.springframework.ui.Model;import org.springframework.web.bind.annotation.RequestMapping;@Controllerpublic class MyController {    //inject this    private Executor executor;    @RequestMapping("/your/path/here")    public String myMVCControllerGETdataMethod(Model model) {        //define all async requests and give them to injected Executor        List<GetRequestTask> tasks = new ArrayList<GetRequestTask>();        tasks.add(new GetRequestTask("http://api/data?type=1", this.executor));        tasks.add(new GetRequestTask("http://api/data?type=2", this.executor));        //...        //do other work here        //...        //now wait for all async tasks to complete        while(!tasks.isEmpty()) { for(Iterator<GetRequestTask> it = tasks.iterator(); it.hasNext();) {     GetRequestTask task = it.next();     if(task.isDone()) {         String request = task.getRequest();         String response = task.getResponse();         //PUT YOUR CODE HERE         //possibly aggregate request and response in Map<String,String>         //or do something else with request and response         it.remove();     } } //avoid tight loop in "main" thread if(!tasks.isEmpty()) Thread.sleep(100);        }        //now you have all responses for all async requests        //the following from your original pre        //note: you should probably pass the responses from above        //to this next method (to keep your controller stateless)        String results = doWorkwithMultipleDataReturned();        model.addAttribute(results, results);        return "index";    }    //abstraction to wrap Callable and Future    class GetRequestTask {        private GetRequestWork work;        private FutureTask<String> task;        public GetRequestTask(String url, Executor executor) { this.work = new GetRequestWork(url); this.task = new FutureTask<String>(work); executor.execute(this.task);        }        public String getRequest() { return this.work.getUrl();        }        public boolean isDone() { return this.task.isDone();        }        public String getResponse() { try {     return this.task.get(); } catch(Exception e) {     throw new RuntimeException(e); }        }    }    //Callable representing actual HTTP GET request    class GetRequestWork implements Callable<String> {        private final String url;        public GetRequestWork(String url) { this.url = url;        }        public String getUrl() { return this.url;        }        public String call() throws Exception { return new DefaultHttpClient().execute(new HttpGet(getUrl()), new BasicResponseHandler());        }    }}

请注意，此代码尚未经过测试。

对于您的

Executor

实现，请查看Spring的TaskExecutor和task：executor名称空间。您可能需要针对此用例的可重用线程池（而不是每次都创建一个新线程）。