代码如下：
package com.juneyao;
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import java.util.ArrayList;
import java.util.Properties;

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


public class einfo extends HttpServlet {
    ArrayList list = new ArrayList();

    public einfo() {
        super();
    }

    public void destroy() {
        super.destroy();
    }

    
    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        doPost(request, response);
    }

    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        response.setContentType("text/xml");
        response.setCharacterEncoding("utf-8");
        PrintWriter out = response.getWriter();
       
       
       
////      查询xml
          String xml="<EticketQueryReq><Sid>hubs</Sid><StartCity>PEK</StartCity>" +
                  "<EndCity>SHA</EndCity><DepTime>20080830</DepTime></EticketQueryReq>";
          
          
         
        String resXml="";
        try {
            resXml=send(xml);
        } catch (Exception e) {
            e.printStackTrace();
        }
                   
        out.print(resXml);
        out.flush();
    }
    
    String send(String xml)throws Exception{
         url = new ("http://www.); //http://192.168.0.151:6666/einfo
         con = url.openConnection(); //http://localhost:8080/portal_v/einfo
        con.setUseCaches(false);
        con.setDoOutput(true);
        con.setDoInput(true);
        /*缓存*/
        BufferedReader fin = new BufferedReader(new StringReader(xml));
        StringBuffer stringbuffer = new StringBuffer();
        byte bt1[] = xml.getBytes("utf-8");
        char ac[] = new char[2048];
        int i;
        while ((i = fin.read(ac)) > 0)
        stringbuffer.append(ac, 0, i);
        fin.close();
        
        
        /*发送*/
        OutputStream dataOut = con.getOutputStream();
        dataOut.write(bt1);
        dataOut.flush();
        dataOut.close();
        /*获取服务器端返回信息*/
        
        InputStream in =con.getInputStream();
        InputStreamReader inreader = new InputStreamReader(in);
        BufferedReader bureader = new BufferedReader(inreader);
        String stringValue = "";
        String resXML="";
        while(( stringValue = bureader.readLine()) != null){
            resXML=resXML+stringValue;
        }
        in.close();
        return resXML;

    }

    
    public void init() throws ServletException {

        
    }
    
}

查一下MSDN吧