wx.login({ success: function (res) { console.log(res.code)； } }）

 //app.js
App({
 globalData: {
 appid: '',
 appsecret: '',//
 openid: ''
 }
 onLaunch: function () {
 var that =this;
 // 登录
 wx.login({
  success: function (res) {
  console.log(res.code)
  wx.request({
   url: 'http://127.0.0.1:8080/jeecg-boot/hwork/hworkLog/GetOpenIdServlet',
   data: {
   appid: that.globalData.appid,
   secret: that.globalData.appsecret,
   js_code: res.code,
   grant_type: 'authorization_code'
   },
   method: 'POST',
   header: {
   'Content-Type': 'application/x-www-form-urlencoded'
   },
   success: function (res) {
   console.log(res)
   //转json
   var j= JSON.parse(res.data.result)
   //获取到openid
   that.globalData.openid = j.openid;
   }
  })
  }
 })
  }
})

package org.jeecg.modules.hworkorder.util;
import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.HttpURLConnection;
import java.net.URL;
public class WeChatService {
 /**
  * 调用对方接口方法
  * @param path 对方或第三方提供的路径
  * @param data 向对方或第三方发送的数据，大多数情况下给对方发送JSON数据让对方解析
  */
 public static String interfaceUtil(String path,String data) {
  String openId="";
  try {
   URL url = new URL(path);
   //打开和url之间的连接
   HttpURLConnection conn = (HttpURLConnection) url.openConnection();
   PrintWriter out = null;
   //请求方式
//   conn.setRequestMethod("POST");
//   //设置通用的请求属性
   conn.setRequestProperty("accept", "*/*");
   conn.setRequestProperty("connection", "Keep-Alive");
   conn.setRequestProperty("user-agent", "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1)");
   //设置是否向httpUrlConnection输出，设置是否从httpUrlConnection读入，此外发送post请求必须设置这两个
   //最常用的Http请求无非是get和post，get请求可以获取静态页面，也可以把参数放在URL字串后面，传递给servlet，
   //post与get的 不同之处在于post的参数不是放在URL字串里面，而是放在http请求的正文内。
   conn.setDoOutput(true);
   conn.setDoInput(true);
   //获取URLConnection对象对应的输出流
   out = new PrintWriter(conn.getOutputStream());
   //发送请求参数即数据
   out.print(data);
   //缓冲数据
   out.flush();
   //获取URLConnection对象对应的输入流
   InputStream is = conn.getInputStream();
   //构造一个字符流缓存
   BufferedReader br = new BufferedReader(new InputStreamReader(is));
   String str = "";
   while ((str = br.readLine()) != null) {
    openId=str;
    System.out.println(str);
   }
   //关闭流
   is.close();
   //断开连接，最好写上，disconnect是在底层tcp socket链接空闲时才切断。如果正在被其他线程使用就不切断。
   //固定多线程的话，如果不disconnect，链接会增多，直到收发不出信息。写上disconnect后正常一些。
   conn.disconnect();
   System.out.println("完整结束");
  } catch (Exception e) {
   e.printStackTrace();
  }
  return openId;
 }
 public static String GetOpenID(String appid,String appsecret,String Code) {
  //临时登录凭证
  String URL = "https://api.weixin.qq.com/sns/jscode2session"+appid+"&secret="+appsecret+"&js_code="+Code+"&grant_type=authorization_code";
  String openId=interfaceUtil(URL, "");
  return openId;
 }
}

@RestController
@RequestMapping("/hwork/hworkLog")
@Slf4j
public class hworkLogContrller {
@RequestMapping(value = "/GetOpenIdServlet", method = RequestMethod.POST)
 public Result<String> GetOpenIdServlet(HttpServletRequest request, HttpServletResponse response){
  Result<String> result=new Result<String>();
  response.setContentType("text/html;charset=utf-8");
  /* 设置响应头允许ajax跨域访问 */
  response.setHeader("Access-Control-Allow-Origin", "*");
  /* 星号表示所有的异域请求都可以接受， */
  response.setHeader("Access-Control-Allow-Methods", "GET,POST");
  //转成json数据
  String appid=request.getParameter("appid");
  String secret=request.getParameter("secret");
  String js_code=request.getParameter("js_code");
  if(appid!=null&&appid!=""&&secret!=null&&secret!=""&&js_code!=null&&js_code!=""){
   WeChatService getOpenId=new WeChatService();
   String openId=getOpenId.GetOpenID(appid,secret,js_code);
   result.setResult(openId);
   result.setMessage("后台收到并返回");
  }else{
   result.setMessage("参数为空");
   result.setSuccess(false);
  }
  return result;
 }
}