微信公众号开发中使用Java如何实现获取用户的信息

package net.itraf.controller;import java.io.IOException;import java.io.InputStream;import java.io.PrintWriter;import java.net.HttpURLConnection;import java.net.MalformedURLException;import java.net.URL;import javax.servlet.http.HttpServletResponse;import org.springframework.stereotype.Controller;import org.springframework.web.bind.annotation.RequestMapping;import org.springframework.web.bind.annotation.ResponseBody;import com.alibaba.fastjson.JSONObject;@Controller@RequestMapping("/open")public class OpenController {  @RequestMapping("/toOpenId")  public @ResponseBody String getOpenId(String code,String echostr,HttpServletResponse res) throws IOException{    if(echostr==null){      String url="https://api.weixin.qq.com/sns/oauth3/access_token?appid=wx24d47d2080f54c5b&secret=95011ac70909e8cca2786217dd80ee3f&code="+code+"&grant_type=authorization_code";      System.out.println(code);      String openId="";      try {        URL getUrl=new URL(url);        HttpURLConnection http=(HttpURLConnection)getUrl.openConnection();        http.setRequestMethod("GET");         http.setRequestProperty("Content-Type","application/x-www-form-urlencoded");        http.setDoOutput(true);        http.setDoInput(true);        http.connect();        InputStream is = http.getInputStream();         int size = is.available();         byte[] b = new byte[size];        is.read(b);        String message = new String(b, "UTF-8");        JSONObject json = JSONObject.parseObject(message);        openId = json.getString("openid");        } catch (MalformedURLException e) {          e.printStackTrace();        } catch (IOException e) {          e.printStackTrace();        }      return openId;    }else{      PrintWriter out = res.getWriter();      out.print(echostr);      return null;    }  }  //做服务器校验  @RequestMapping("/tovalid")  public void valid(String echostr,HttpServletResponse res) throws IOException{    PrintWriter out = res.getWriter();    out.print(echostr);  }}