java后台获取openid（小程序开发前端+后台）-即速应用

前台需要request后台Servlet响应

data:{ } 传值，需要有appid ， appsecret ，js_code(临时登录凭证)

需要把openid设置为全局变量，不重复获取

获取openid之前，确保appid正确，且与配置文件中的appid一致。

前端app.js代码如下，全局数据需要根据自己的填写。

//app.jsApp({  globalData: {    requestURL: 'http://localhost:8080',//请求地址    appid: '',    appsecret: '',//    userInfo: null,    openid: ''  },  onLaunch: function () {    var logs = wx.getStorageSync('logs') || []    logs.unshift(Date.now())    wx.setStorageSync('logs', logs)    var that = this;    wx.login({      success: function (res) {        console.log(res.code);        wx.request({          url: 'http://localhost:8080/CloudExplorer/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)            var OPEN_ID = res.data.openId;//获取到的openid            that.globalData.openid = res.data.openId;            console.log(that.globalData.openid)          }        })      }    })    wx.getSetting({      success: res => {        if (res.authSetting['scope.userInfo']) {          wx.getUserInfo({            success: res => {              this.globalData.userInfo = res.userInfo              if (this.userInfoReadyCallback) {                this.userInfoReadyCallback(res)              }            }          })        }      }    })  }})

后台Servlet需要调用WeChatService类中获取openid的函数

Servlet写法如下：

package cloud.Servlet;import java.io.IOException;import java.io.Writer;import java.util.HashMap;import java.util.Map;import javax.servlet.ServletException;import javax.servlet.annotation.WebServlet;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import com.google.gson.Gson;import cloud.Service.*;@WebServlet(urlPatterns={"/GetOpenIdServlet"})public class GetOpenIdServlet extends HttpServlet {    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {        //设置请求编码        request.setCharacterEncoding("utf-8");        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");                WeChatService getOpenId=new WeChatService();        String openId=getOpenId.GetOpenID(appid,secret,js_code);        Map<String, String> result = new HashMap<String, String>();;        result.put("openId",openId);        result.put("msg", "后台已收到");        String json = new Gson().toJson(result);        //返回值给微信小程序        Writer out = response.getWriter();        out.write(json);        out.flush();    }    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {        doGet(request, response);    }}

WeChatService类的写法如下：

package cloud.Service;import java.io.BufferedReader;import java.io.InputStream;import java.io.InputStreamReader;import java.io.PrintWriter;import java.net.HttpURLConnection;import java.net.URL;/** * @author chd * @QQ:1025584691 */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="+appid+"&secret="+appsecret+"&js_code="+Code+"&grant_type=authorization_code";    String openId=interfaceUtil(URL, "");    return openId;    }}