我在
spring mvc 3.2.2中使用apache http客户端,如图所示同步发送5个get请求.
如何异步(并行)发送所有这些异常并等待请求返回,以便从所有GET请求返回解析的有效负载字符串？
public String myMVCControllerGETdataMethod()
{
// Send 1st request
HttpClient httpclient = new DefaultHttpClient();
HttpGet httpget = new HttpGet("http://api/data?type=1");
ResponseHandler<String> responseHandler = new BasicResponseHandler();
String responseBody = httpclient.execute(httpget,responseHandler);
// Send 2st request
HttpClient httpclient2 = new DefaultHttpClient();
HttpGet httpget2 = new HttpGet("http://api/data?type=2");
ResponseHandler2<String> responseHandler2 = new BasicResponseHandler();
String responseBody2 = httpclient.execute(httpget,responseHandler2);
// o o o more gets here
// Perform some work here...and wait for all requests to return
// Parse info out of multiple requests and return
String results = doWorkwithMultipleDataReturned();
model.addAttribute(results,results);
return "index";
}
解决方法
通常,您需要将您的工作单元封装在Runnable或java.util.concurrent.Callable中,并通过java.util.concurrent.Executor(或org.springframework.core.task.TaskExecutor)执行它们.这允许每个单元的工作单独执行,通常以异步方式执行(取决于执行程序的实现).
所以对于你的具体问题,你可以这样做：
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;
@Controller
public 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 code
//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,此代码尚未测试.
对于您的Executor实现,请查看Spring’s TaskExecutor和task:executor namespace.您可能需要一个可重用的线程池用于此用例(而不是每次都创建一个新线程).
