Jetty + HttpClient 处理http请求

本人最近通过自己动手处理http请求，对http协议、Jetty以及HttpClient有了更深刻的理解，特在此与大家分享。

此图是http协议的请求格式。根据请求方法，有get和post之分。get和post的区别在于参数传递的方式：post的参数就是请求包体那一行；get的参数跟在URL后面，也就没有请求包体。

get方式的请求格式

GET /search?hl=zh-CN&source=hp&q=domety&aq=f&oq= HTTP/1.1
Accept: image/gif, image/x-xbitmap, image/jpeg, image/pjpeg, application/vnd.ms-excel, application/vnd.ms-powerpoint, 
application/msword, application/x-silverlight, application/x-shockwave-flash, */*
Referer: <a href="http://www.google.cn/">http://www.google.cn/</a>
Accept-Language: zh-cn
Accept-Encoding: gzip, deflate
User-Agent: Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; .NET CLR 2.0.50727; TheWorld)
Host: <a href="http://www.google.cn">www.google.cn</a>
Connection: Keep-Alive
Cookie: PREF=ID=80a06da87be9ae3c:U=f7167333e2c3b714:NW=1:TM=1261551909:LM=1261551917:S=ybYcq2wpfefs4V9g; 
NID=31=ojj8d-IygaEtSxLgaJmqSjVhCspkviJrB6omjamNrSm8lZhKy_yMfO2M4QMRKcH1g0iQv9u-2hfBW7bUFwVh7pGaRUb0RnHcJU37y-
FxlRugatx63JLv7CWMD6UB_O_r 

post方式的请求格式

POST /search HTTP/1.1
Accept: image/gif, image/x-xbitmap, image/jpeg, image/pjpeg, application/vnd.ms-excel, application/vnd.ms-powerpoint, 
application/msword, application/x-silverlight, application/x-shockwave-flash, */*
Referer: <a href="http://www.google.cn/">http://www.google.cn/</a>
Accept-Language: zh-cn
Accept-Encoding: gzip, deflate
User-Agent: Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; .NET CLR 2.0.50727; TheWorld)
Host: <a href="http://www.google.cn">www.google.cn</a>
Connection: Keep-Alive
Cookie: PREF=ID=80a06da87be9ae3c:U=f7167333e2c3b714:NW=1:TM=1261551909:LM=1261551917:S=ybYcq2wpfefs4V9g; 
NID=31=ojj8d-IygaEtSxLgaJmqSjVhCspkviJrB6omjamNrSm8lZhKy_yMfO2M4QMRKcH1g0iQv9u-2hfBW7bUFwVh7pGaRUb0RnHcJU37y-
FxlRugatx63JLv7CWMD6UB_O_r  

hl=zh-CN&source=hp&q=domety

所以，对请求进行解析的时候需要区分。

1、用Jetty捕获请求

直接上代码

 package test;
 import org.eclipse.jetty.server.Request;
 import org.eclipse.jetty.server.Server;
 import org.eclipse.jetty.server.handler.AbstractHandler;

 import javax.servlet.ServletException;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;  

 public class JettyServer {
     public static void main(String[] args) {
         try {
             // 进行服务器配置
             Server server = new Server(8888);
             server.setHandler(new MyHandler());
             // 启动服务器
             server.start();
             server.join();
         } catch (Exception e) {
             e.printStackTrace();
         }
     }
 }  

 class MyHandler extends AbstractHandler {

     @Override
     public void handle(String target, Request baseRequest,
         HttpServletRequest request, HttpServletResponse response)
         throws IOException, ServletException {
         //写自己的处理
     }  

 } 

Jetty类似于tomcat，但是Jetty比较轻量级，特别适合内嵌到自己写的程序中，比如Hadoop的内置Server就是Jetty。

Jetty将请求进行了封装，比如Jetty自己的Request类，以及我们熟悉的HttpServletRequest类；并且把对象传递给handler。我们拿到HttpServletRequest的对象，就可以对请求进行解析、修改和拼装

Enumeration params = request.getParameterNames();
        while(params.hasMoreElements()){
            String paraName = (String)params.nextElement();
            String paraValue = request.getParameter(paraName);
            paramList.add(new BasicNameValuePair(paraName, paraValue));
        }

Enumeration headerNames = request.getHeaderNames();
        while (headerNames.hasMoreElements()) {
            String headerName = (String) headerNames.nextElement();
                //HttpClient会自动加上这个请求头
            if(headerName.equals("Content-Length")) {
                continue;
            }
            String headerValue = request.getHeader(headerName);
            Header header = new BasicHeader(headerName, headerValue);
            headers.add(header);
        }

2、用HttpClient转发请求

把捕获的请求进行重新组装之后，就可以通过HttpClient转发出去。

HttpClient 是 Apache Jakarta Common 下的子项目，可以用来提供高效的、最新的、功能丰富的支持 HTTP 协议的客户端编程工具包。多说无益，简单语法请自行百度。

下面是一个完整的加入了HttpClient进行请求转发的类

 package service;
 import java.io.BufferedReader;
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.InputStreamReader;
 import java.io.UnsupportedEncodingException;
 import java.util.ArrayList;
 import java.util.Enumeration;
 import java.util.List;

 import javax.servlet.http.HttpServletRequest;

 import org.apache.http.Header;
 import org.apache.http.HttpEntity;
 import org.apache.http.HttpResponse;
 import org.apache.http.NameValuePair;
 import org.apache.http.client.ClientProtocolException;
 import org.apache.http.client.HttpClient;
 import org.apache.http.client.entity.UrlEncodedFormEntity;
 import org.apache.http.client.methods.HttpGet;
 import org.apache.http.client.methods.HttpPost;
 import org.apache.http.client.methods.HttpUriRequest;
 import org.apache.http.impl.client.DefaultHttpClient;
 import org.apache.http.message.BasicHeader;
 import org.apache.http.message.BasicNameValuePair;  

 public class RequestSender implements Runnable {
     private HttpClient httpclient = null;
     private RequestAdaptor requestAdaptor = null;//封装之后的请求
     private String ip = null;
     private String port = null;

     public RequestSender(RequestAdaptor requestAdaptor, String ip, String port) {
         httpclient = new DefaultHttpClient();
         this.requestAdaptor = requestAdaptor;
         this.ip = ip;
         this.port = port;
     }

     @Override
     public void run() {
         send();
     }

     public void send() {
         if(requestAdaptor == null) {
             return;
         }
         String method = requestAdaptor.getMethod();
         String uri = requestAdaptor.getUri();
         String host = ip + ":" + port;
         String url = "http://" + host + uri;
         if(method.equals("GET")) {
             get(url);
         }else if(method.equals("POST")) {
             post(url);
         }
     }

     public void get(String url) {
         url = url + "?" + requestAdaptor.getQueryString();
         HttpGet httpGet = new HttpGet(url);
         addHeaders(httpGet);
         try{

             HttpResponse resp = httpclient.execute(httpGet);
             System.out.println(resp.getStatusLine().getStatusCode());
         }catch(ClientProtocolException cp) {
             cp.printStackTrace();
         }catch(IOException io) {
             io.printStackTrace();
         }
         //return showResponse(httpGet);
     }

     public void post(String url) {
         System.out.println(url);
         HttpPost httpPost = new HttpPost(url);
         addHeaders(httpPost);
         UrlEncodedFormEntity uefEntity = null;
         try {
             uefEntity = new UrlEncodedFormEntity(requestAdaptor.getParamList(), "UTF-8");
         } catch (UnsupportedEncodingException e) {
             e.printStackTrace();
         }
         httpPost.setEntity(uefEntity);
         try{
             HttpResponse resp = httpclient.execute(httpPost);
             System.out.println(resp.getStatusLine().getStatusCode());
         }catch(ClientProtocolException cp) {
             cp.printStackTrace();
         }catch(IOException io) {
             io.printStackTrace();
         }
         //return showResponse(httpPost);
     }

     public void addHeaders(HttpUriRequest httpUriRequest) {
         List<Header> headers = requestAdaptor.getHeaders();
         for(int i = 0 ; i< headers.size();i++){
             httpUriRequest.addHeader(headers.get(i));
         }
     }

     public String showResponse(HttpUriRequest httpUriRequest) {
         HttpResponse response = null;
         try {
             response = httpclient.execute(httpUriRequest);
         } catch (ClientProtocolException e) {
             e.printStackTrace();
         } catch (IOException e) {
             e.printStackTrace();
         }
         HttpEntity entity = response.getEntity();
         if (entity != null) {
             InputStream instreams = null;
             try {
                 instreams = entity.getContent();
             } catch (UnsupportedOperationException e) {
                 e.printStackTrace();
             } catch (IOException e) {
                 e.printStackTrace();
             }
             String str = convertStreamToString(instreams);
             //System.out.println(str);
             // Do not need the rest
             httpUriRequest.abort();
             return str;
         }
         return null;
     }

     public static String convertStreamToString(InputStream is) {
         BufferedReader reader = new BufferedReader(new InputStreamReader(is));
         StringBuilder sb = new StringBuilder();
         String line = null;
         try {
             while ((line = reader.readLine()) != null) {
                 sb.append(line + "\n");
             }
         } catch (IOException e) {
             e.printStackTrace();
         } finally {
             try {
                 is.close();
             } catch (IOException e) {
                e.printStackTrace();
             }
         }
         return sb.toString();
     }
 }

转发的核心是httpclient.execute(httpGet)和httpclient.execute(httpPost)

转发post请求的时候，需要把参数一个一个的组装进去；而转发get请求的时候就不用，应为参数已经跟在URL后面。但是，无论get还是post，都需要把请求头原封不动的组装进去。

基于以上两点，我们可以做的事情就有很多了。