URLConnection传递参数后的问题

现在有需求需要用java的URLConnection发送请求并传递参数，就在网上找了代码来研究。代码如下：

[color=green]import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
import java.net.URLEncoder;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Map.Entry;

import org.apache.log4j.Logger;

/**

  • HTTP请求[qing qiu]代理类
  • @author benl
  • @version 1.0, 2007-7-3
    */
    public class HttpRequestProxy {
    /**
    • 连接[lian jie]超时[chao shi] */ private static int connectTimeOut = 5000;
    /**
    • 读取[du qu]数据[shu ju]超时[chao shi] */ private static int readTimeOut = 10000;
    /**
    • 请求[qing qiu]编码[bian ma] */ private static String requestEncoding = "GBK";
    private static Logger logger = Logger.getLogger(HttpRequestProxy.class);
    /**
    • 发送带参数[can shu]的GET的HTTP请求[qing qiu]
    • @param reqUrl
    • HTTP请求[qing qiu]URL
    • @param parameters
    • 参数[can shu]映射[ying she]表
    • @return HTTP响应[xiang ying]的字符[zi fu]串[zi fu chuan]
      */
      public static String doGet(String reqUrl, Map parameters,
      String recvEncoding) {
      HttpURLConnection url_con = null;
      String responseContent = null;
      try {
      StringBuffer params = new StringBuffer();
      for (Iterator iter = parameters.entrySet().iterator(); iter
      .hasNext();) {
      Entry element = (Entry) iter.next();
      params.append(element.getKey().toString());
      params.append("=");
      params.append(URLEncoder.encode(element.getValue().toString(),
      HttpRequestProxy.requestEncoding));
      params.append("&");
      }
      if (params.length() > 0) {
    params = params.deleteCharAt(params.length() - 1);
}

URL url = new URL(reqUrl);
url_con = (HttpURLConnection) url.openConnection();
url_con.setRequestMethod("GET");
System.setProperty("sun.net.client.defaultConnectTimeout", String
        .valueOf(HttpRequestProxy.connectTimeOut));// （单位[dan
                                                    // wei]：毫秒）jdk1.4换成这个,连接[lian
                                                    // jie]超时[chao
                                                    // shi]
System.setProperty("sun.net.client.defaultReadTimeout", String
        .valueOf(HttpRequestProxy.readTimeOut)); // （单位[dan
                                                    // wei]：毫秒）jdk1.4换成这个,读操作超时[chao
                                                    // shi]
// url_con.setConnectTimeout(5000);//（单位[dan wei]：毫秒）jdk
// 1.5换成这个,连接[lian jie]超时[chao shi]
// url_con.setReadTimeout(5000);//（单位[dan wei]：毫秒）jdk
// 1.5换成这个,读操作超时[chao shi]
url_con.setDoOutput(true);
byte[] b = params.toString().getBytes();
url_con.getOutputStream().write(b, 0, b.length);
url_con.getOutputStream().flush();
url_con.getOutputStream().close();

InputStream in = url_con.getInputStream();
BufferedReader rd = new BufferedReader(new InputStreamReader(in,
        recvEncoding));
String tempLine = rd.readLine();
StringBuffer temp = new StringBuffer();
String crlf = System.getProperty("line.separator");
while (tempLine != null) {
    temp.append(tempLine);
    temp.append(crlf);
    tempLine = rd.readLine();
}
responseContent = temp.toString();
rd.close();
in.close();

      } catch (IOException e) {
      logger.error("网络[wang luo]故障[gu zhang]", e);
      } finally {
      if (url_con != null) {
    url_con.disconnect();
}

      }
      return responseContent;
      }
    /**
    • 发送不带参数[can shu]的GET的HTTP请求[qing qiu]
    • @param reqUrl
    • HTTP请求[qing qiu]URL
    • @return HTTP响应[xiang ying]的字符[zi fu]串[zi fu chuan]
      */
      public static String doGet(String reqUrl, String recvEncoding) {
      HttpURLConnection url_con = null;
      String responseContent = null;
      try {
      StringBuffer params = new StringBuffer();
      String queryUrl = reqUrl;
      int paramIndex = reqUrl.indexOf("?");
      if (paramIndex > 0) {
    queryUrl = reqUrl.substring(0, paramIndex);
    String parameters = reqUrl.substring(paramIndex + 1, reqUrl
            .length());
    String[] paramArray = parameters.split("&");
    for (int i = 0; i < paramArray.length; i++) {
        String string = paramArray[i];
        int index = string.indexOf("=");

        if (index > 0) {
            String parameter = string.substring(0, index);
            String value = string.substring(index + 1, string
                    .length());
            params.append(parameter);
            params.append("=");
            params.append(URLEncoder.encode(value,
                    HttpRequestProxy.requestEncoding));
            params.append("&");
        }
    }

    params = params.deleteCharAt(params.length() - 1);
}

URL url = new URL(queryUrl);
url_con = (HttpURLConnection) url.openConnection();
url_con.setRequestMethod("GET");
System.setProperty("sun.net.client.defaultConnectTimeout", String
        .valueOf(HttpRequestProxy.connectTimeOut));// （单位[dan
                                                    // wei]：毫秒）jdk1.4换成这个,连接[lian
                                                    // jie]超时[chao
                                                    // shi]
System.setProperty("sun.net.client.defaultReadTimeout", String
        .valueOf(HttpRequestProxy.readTimeOut)); // （单位[dan
                                                    // wei]：毫秒）jdk1.4换成这个,读操作超时[chao
                                                    // shi]
// url_con.setConnectTimeout(5000);//（单位[dan wei]：毫秒）jdk
// 1.5换成这个,连接[lian jie]超时[chao shi]
// url_con.setReadTimeout(5000);//（单位[dan wei]：毫秒）jdk
// 1.5换成这个,读操作超时[chao shi]
url_con.setDoOutput(true);
byte[] b = params.toString().getBytes();
url_con.getOutputStream().write(b, 0, b.length);
url_con.getOutputStream().flush();
url_con.getOutputStream().close();
InputStream in = url_con.getInputStream();
BufferedReader rd = new BufferedReader(new InputStreamReader(in,
        recvEncoding));
String tempLine = rd.readLine();
StringBuffer temp = new StringBuffer();
String crlf = System.getProperty("line.separator");
while (tempLine != null) {
    temp.append(tempLine);
    temp.append(crlf);
    tempLine = rd.readLine();
}
responseContent = temp.toString();
rd.close();
in.close();

      } catch (IOException e) {
      logger.error("网络[wang luo]故障[gu zhang]", e);
      } finally {
      if (url_con != null) {
    url_con.disconnect();
}

      }
      return responseContent;
      }
    /**
    • 发送带参数[can shu]的POST的HTTP请求[qing qiu]
    • @param reqUrl
    • HTTP请求[qing qiu]URL
    • @param parameters
    • 参数[can shu]映射[ying she]表
    • @return HTTP响应[xiang ying]的字符[zi fu]串[zi fu chuan]
      */
      public static String doPost(String reqUrl, Map parameters,
      String recvEncoding) {
      HttpURLConnection url_con = null;
      String responseContent = null;
      try {
      StringBuffer params = new StringBuffer();
      for (Iterator iter = parameters.entrySet().iterator(); iter
      .hasNext();) {
      Entry element = (Entry) iter.next();
      params.append(element.getKey().toString());
      params.append("=");
      params.append(URLEncoder.encode(element.getValue().toString(),
      HttpRequestProxy.requestEncoding));
      params.append("&");
      }
      if (params.length() > 0) {
    params = params.deleteCharAt(params.length() - 1);
}

URL url = new URL(reqUrl);
url_con = (HttpURLConnection) url.openConnection();
url_con.setRequestMethod("POST");
System.setProperty("sun.net.client.defaultConnectTimeout", String
        .valueOf(HttpRequestProxy.connectTimeOut));// （单位[dan
                                                    // wei]：毫秒）jdk1.4换成这个,连接[lian
                                                    // jie]超时[chao
                                                    // shi]
System.setProperty("sun.net.client.defaultReadTimeout", String
        .valueOf(HttpRequestProxy.readTimeOut)); // （单位[dan
                                                    // wei]：毫秒）jdk1.4换成这个,读操作超时[chao
                                                    // shi]
// url_con.setConnectTimeout(5000);//（单位[dan wei]：毫秒）jdk
// 1.5换成这个,连接[lian jie]超时[chao shi]
// url_con.setReadTimeout(5000);//（单位[dan wei]：毫秒）jdk
// 1.5换成这个,读操作超时[chao shi]
url_con.setDoOutput(true);
byte[] b = params.toString().getBytes();
url_con.getOutputStream().write(b, 0, b.length);
url_con.getOutputStream().flush();
url_con.getOutputStream().close();

InputStream in = url_con.getInputStream();
BufferedReader rd = new BufferedReader(new InputStreamReader(in,
        recvEncoding));
String tempLine = rd.readLine();
StringBuffer tempStr = new StringBuffer();
String crlf = System.getProperty("line.separator");
while (tempLine != null) {
    tempStr.append(tempLine);
    tempStr.append(crlf);
    tempLine = rd.readLine();
}
responseContent = tempStr.toString();
rd.close();
in.close();

      } catch (IOException e) {
      logger.error("网络[wang luo]故障[gu zhang]", e);
      } finally {
      if (url_con != null) {
    url_con.disconnect();
}

      }
      return responseContent;
      }
    /**
    • @return 连接[lian jie]超时chao shi
    • @see com.hengpeng.common.web.HttpRequestProxy#connectTimeOut */ public static int getConnectTimeOut() { return HttpRequestProxy.connectTimeOut; }
    /**
    • @return 读取[du qu]数据[shu ju]超时chao shi
    • @see com.hengpeng.common.web.HttpRequestProxy#readTimeOut */ public static int getReadTimeOut() { return HttpRequestProxy.readTimeOut; }
    /**
    • @return 请求[qing qiu]编码[bian ma]
    • @see com.hengpeng.common.web.HttpRequestProxy#requestEncoding */ public static String getRequestEncoding() { return requestEncoding; }
    /**
    • @param connectTimeOut
    • 连接[lian jie]超时chao shi
    • @see com.hengpeng.common.web.HttpRequestProxy#connectTimeOut */ public static void setConnectTimeOut(int connectTimeOut) { HttpRequestProxy.connectTimeOut = connectTimeOut; }
    /**
    • @param readTimeOut
    • 读取[du qu]数据[shu ju]超时chao shi
    • @see com.hengpeng.common.web.HttpRequestProxy#readTimeOut */ public static void setReadTimeOut(int readTimeOut) { HttpRequestProxy.readTimeOut = readTimeOut; }
    /**
    • @param requestEncoding
    • 请求[qing qiu]编码[bian ma]
    • @see com.hengpeng.common.web.HttpRequestProxy#requestEncoding */ public static void setRequestEncoding(String requestEncoding) { HttpRequestProxy.requestEncoding = requestEncoding; }
    public static void main(String[] args) {
    Map map = new HashMap();
    map.put("actionType", "1");
    map.put("issueId", "33");
    String temp = HttpRequestProxy.doGet(
    "http://localhost/TransData", map, "GBK");
    System.out.println("返回的消息[xiao xi]是:" + temp);
    }
    }[/color]
最后mian方法中这段
String temp = HttpRequestProxy.doGet("http://localhost/TransData", map, "GBK");
里面的URL是我另外新建的一个web工程，名为TransData。在TransData工程中的index.jsp页面我这样写：
[color=green]<%
String p1 = request.getParameter("actionType");
String p2 = request.getParameter("issueId");
System.out.println("p1:"+p1);
System.out.println("p2:"+p2);
%>[/color]
但是发现我拿不到参数。
就把提交的URL改为提交到servlet：
String temp = HttpRequestProxy.doGet("http://localhost/TransData/a.do", map, "GBK");
在servlet的doPost方法中这样写：
[color=green] String p1 = req.getParameter("actionType");
String p2 = req.getParameter("issueId");
System.out.println(p1);
System.out.println(p2);[/color]
这样打印p1,p2发现可以拿到值。这是为什么呢，为什么在jsp中拿不到参数，在servlet中却可以拿到？
可能http://localhost/TransData到index页面中出现是forward跳转导致参数丢失吧