项目中用到，这里把它给简化和通用了，突出基本思路，具体可以基于这个类来修改。

基于java容器和servlet。

package com.xxx.first;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.net.HttpURLConnection;
import java.net.URL;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.commons.compress.utils.IOUtils;

public class SimpleProxy {

    /**
     * 使用GET提交到目标服务器。
     * 
     * @param request
     * @param response
     * @param targetUrl
     * @throws IOException
     */
    private void get(HttpServletRequest request, HttpServletResponse response,
	    String targetUrl) throws IOException {

	URL url = new URL(targetUrl);
	

	BufferedReader in = new BufferedReader(new InputStreamReader(
		url.openStream()));

	String line;
	PrintWriter out = response.getWriter();
	while ((line = in.readLine()) != null) {
	    out.println(line);
	}
	out.flush();
	in.close();
    }

    /**
     * 使用POST提交到目标服务器。
     * 
     * @param request
     * @param response
     * @param targetUrl
     * @throws IOException
     */
    private void post(HttpServletRequest request, HttpServletResponse response,
	    String targetUrl) throws IOException {
	URL url = new URL(targetUrl);
	HttpURLConnection conn = (HttpURLConnection) url.openConnection();

	// 发送POST请求必须设置如下两行
	conn.setDoOutput(true);
	conn.setDoInput(true);
	conn.setRequestMethod("POST");
	// 可以拷贝客户端的head信息作为请求的head参数
	// conn.setRequestProperty("Charsert", "UTF-8");
	conn.setRequestProperty("Content-Type", "application/json");

	// 直接把客户端的BODY传给目标服务器
	OutputStream send = conn.getOutputStream();
	InputStream body = request.getInputStream();
	IOUtils.copy(body, send);
	send.flush();
	send.close();
	body.close();

	// 获取返回值
	BufferedReader in = new BufferedReader(new InputStreamReader(
		conn.getInputStream()));
	PrintWriter out = response.getWriter();
	String line;
	while ((line = in.readLine()) != null) {
	    out.println(line);
	}
	out.flush();
    }

}

一个可以作为代理服务器或者转发的java类