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 + "
");      
            }      
        } 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。