微信小程序获取openId(JAVA)

openId是微信用户的唯一标识

官方文档：小程序登陆

1、app.js

onLaunch: function () {
    // 展示本地存储能力
    this.getUserOpenId();
}
getUserOpenId: function(callback) {
    var self = this
    if (self.globalData.openid) {
      callback(null, self.globalData.openid)
    } else {
      wx.login({
        success: function(data) {
          wx.request({
            url: self.globalData.URL+"/wxLoginController/getWxOpenId.json?code="+data.code,
            method:"POST",
            success: function(res) {
              console.log('拉取openid成功', res.data)
              self.globalData.openid = res.data.openid
            },
            fail: function(res) {
              console.log('拉取用户openid失败，将无法正常使用开放接口等服务', res)
            }
          })
        },
        fail: function(err) {
          console.log('wx.login 接口调用失败，将无法正常使用开放接口等服务', err)
        }
      })
    }
  },

2、wxLoginController.java

@RequestMapping(value = "/getWxOpenId.json", method = RequestMethod.POST)
    @ResponseBody
    public JSONObject getWxOpenId(HttpServletRequest request){
        String code=request.getParameter("code");
        String APPID="";
        //密钥
        String SECRET="";
        //请求微信api获取用户的openid和sessionKey
        JSONObject jsonObject = getUserWXLoginInfo(code,APPID,SECRET);
        return jsonObject;
    }

    private JSONObject getUserWXLoginInfo(String wxCode,String AppID,String AppSecret) {
        String requestUrl = "https://api.weixin.qq.com/sns/jscode2session";
        Map<String,String> requestUrlParam = new HashMap<String,String>();
        requestUrlParam.put("appid",AppID);	//开发者设置中的appId
        requestUrlParam.put("secret", AppSecret);	//开发者设置中的appSecret
        requestUrlParam.put("js_code", wxCode);	//小程序调用wx.login返回的code
        requestUrlParam.put("grant_type", "authorization_code");	//默认参数
        //发送post请求读取调用微信 https://api.weixin.qq.com/sns/jscode2session 接口获取openid用户唯一标识
        JSONObject jsonObject = JSON.parseObject(UrlUtil.sendPost(requestUrl, requestUrlParam));
        return jsonObject;
    }

3、UrlUtil.java

public class UrlUtil {
    private final Logger LOG = LogManager.getLogger(this.getClass());

    /**
     * 向指定 URL 发送POST方法的请求
     *
     * @param url 发送请求的 URL
     * @param paramMap 请求参数
     * @return 所代表远程资源的响应结果
     */
    public static String sendPost(String url, Map<String, ?> paramMap) {
        PrintWriter out = null;
        BufferedReader in = null;
        String result = "";

        String param = "";
        Iterator<String> it = paramMap.keySet().iterator();

        while(it.hasNext()) {
            String key = it.next();
            param += key + "=" + paramMap.get(key) + "&";
        }

        try {
            URL realUrl = new URL(url);
            // 打开和URL之间的连接
            URLConnection conn = realUrl.openConnection();
            // 设置通用的请求属性
            conn.setRequestProperty("accept", "*/*");
            conn.setRequestProperty("connection", "Keep-Alive");
            conn.setRequestProperty("Accept-Charset", "utf-8");
            conn.setRequestProperty("user-agent", "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1;SV1)");
            // 发送POST请求必须设置如下两行
            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
            out.print(param);
            // flush输出流的缓冲
            out.flush();
            // 定义BufferedReader输入流来读取URL的响应
            in = new BufferedReader(new InputStreamReader(conn.getInputStream(), "UTF-8"));
            String line;
            while ((line = in.readLine()) != null) {
                result += line;
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
        //使用finally块来关闭输出流、输入流
        finally{
            try{
                if(out!=null){
                    out.close();
                }
                if(in!=null){
                    in.close();
                }
            }
            catch(IOException ex){
                ex.printStackTrace();
            }
        }
        return result;
    }

}