PC端微信扫码关注公众号并登录

碰到这样一个需求，PC端生成公众号二维码，用户用手机微信扫描，如果用户未关注公众号，则关注公众号后自动登录，如果用户已经关注过公众号，则直接登录。

前端Vue，后端Java实现

分2步来完成：

1.生成带参数的临时二维码

https://developers.weixin.qq.com/doc/offiaccount/Account_Management/Generating_a_Parametric_QR_Code.html

2. 公众号后台服务监听扫码事件并获取用户信息

https://developers.weixin.qq.com/doc/offiaccount/Message_Management/Receiving_event_pushes.html

https://developers.weixin.qq.com/doc/offiaccount/User_Management/Get_users_basic_information_UnionID.html#UinonId

1.生成带参数的临时二维码

获取临时二维码的接口为微信官方提供的 

https://api.weixin.qq.com/cgi-bin/qrcode/create?access_token=TOKEN，注意为POST方式

@RequestMapping("/getQRCode")
    public Map<String,Object> getQRCode(HttpServletRequest request,String code) {
		Map<String,Object> map = new HashMap<String,Object>();
		String code_url = "https://api.weixin.qq.com/cgi-bin/qrcode/create?access_token=TOKEN";
		try{
            //获取公众号的Token,自行实现，我是定任务获取，存到了数据库
			PcAccessToken token = accessTokenService.findPcToken("");
			code_url = code_url.replace("TOKEN", token.getAccessToken());
			String scene_id = (System.currentTimeMillis()+"").substring(0,10);
			JSONObject json = new JSONObject();
			json.put("expire_seconds", "36000");
			json.put("action_name", "QR_SCENE");
			JSONObject info = new JSONObject();
			JSONObject scen = new JSONObject();
			scen.put("scene_id", scene_id);
			info.put("scene", scen);
			json.put("action_info", info);
			String data = HttpUtil.requestPost(code_url, json.toString());
			JSONObject resp = JSONObject.fromObject(data);
			System.out.println("data=="+data);
			map.put("data", resp);
			map.put("scene_id", scene_id);
			map.put("succ", "1");
		} catch(Exception e){
			map.put("succ", "0");
			e.printStackTrace();
		}
        return map;
    }

请求微信接口返回的数据，url参数即为二维码地址，和scene_id一起返回给前端。

前端vue使用 qrcodejs2组件，将url转为二维码图片，显示在相应位置。请求到二维码后，用sceneId查询扫码登录是否成功。

 
<div class="" id="qrcode" ref="qrcode"></div>
 
import QRCode from ''qrcodejs2''
import loginApi from ''@/api/login'';
  data(){
    return{
      url: '''', //二维码地址
      sceneId:'''',//二维码带的参数，用来判断是那个用户扫码的
      timer: null,//定时器
    }
  },
  created(){
    getLoginQRCode();
  },
  methods:{
    async getLoginQRCode(){
      this.url = '''';
      window.clearInterval(this.timer);
      const res = await loginApi.getQRCode();
      console.log(''44res'',res)
      if(res.data.succ == ''1''){
        this.url = res.data.data.url;
        this.sceneId = res.data.scene_id;
        console.log(''sceneId'',res.data.scene_id);
        this.timer = setInterval(this.getUserByScene, 1000);
        this.$nextTick(() => {
          this.getQrcode(this.url)
        })
      }
    },
    //根据 sceneId 轮询查询用户信息，判断用户是否登录成功
    async getUserByScene(){
      if(!this.sceneId) return;
      const res = await loginApi.getUserBySceneId({sceneId: this.sceneId});
      console.log(''getUser'', res);
      if(res.data.succ == ''1'' && res.data.user){
        this.user = res.data.user;
        window.clearInterval(this.timer);
        this.url = '''';
        this.sceneId = '''';
        //登录成功，处理登录成功逻辑
        this.$Message.success(''登录成功'')
      }
    },
    getQrcode (text) {
      this.$refs.qrcode.innerHTML = '''' // 清除
      const qrcode = new QRCode(''qrcode'', {
        width: 160,
        height: 160,
        text: text, // 二维码地址
        colorDark: ''#000'',
        colorLight: ''#fff''
      })
      return qrcode
    },
  }

2.公众号后台服务监听扫码事件并获取用户信息

这块要在微信公众平台配置服务地址信息

开发—基本配置

服务器配置信息提交的时候要验证 TOKEN,  验证通过才能提交。checkToken接口GET请求用来验证TOKEN，

import java.security.MessageDigest;
//...
@RequestMapping(value="/checkToken",method=RequestMethod.GET)
    public String  checkToken(HttpServletRequest req, HttpServletResponse resp)throws IOException {
        req.setCharacterEncoding("UTF-8");
        resp.setCharacterEncoding("UTF-8");
        String message = "success";
        String signature = req.getParameter("signature");
        String timestamp = req.getParameter("timestamp");
        String nonce = req.getParameter("nonce");
        String echostr = req.getParameter("echostr");
        try {
        	String[] arr = {"sjyx", timestamp, nonce};
            Arrays.sort(arr);
 
            StringBuilder content = new StringBuilder();
            for (int i = 0; i < arr.length; i++) {
                content.append(arr[i]);
            }
            //sha1Hex 加密
            MessageDigest md = null;
            String temp = null;
            md = MessageDigest.getInstance("SHA-1");
            byte[] digest = md.digest(content.toString().getBytes());
            temp = byteToStr(digest);
            if ((temp.toLowerCase()).equals(signature)){
                return echostr;
            }
            return null;
        } catch (Exception e) {
            e.printStackTrace();
        }
        return message;
	}
	 private static String byteToStr(byte[] byteArray){
        String strDigest = "";
        for (int i = 0; i < byteArray.length; i++) {
            strDigest += byteToHexStr(byteArray[i]);
        }
        return strDigest;
    }
    private static String byteToHexStr(byte mByte){
        char[] Digit = {''0'', ''1'', ''2'', ''3'', ''4'', ''5'', ''6'', ''7'', ''8'', ''9'', ''A'',''B'', ''C'', ''D'', ''E'', ''F'' };
        char[] tempArr = new char[2];
        tempArr[0] = Digit[(mByte >>> 4)& 0X0F];
        tempArr[1] = Digit[mByte & 0X0F];
        String s = new String(tempArr);
        return s;
    }

checkToken接口POST请求用来监听扫码事件，并获取用户信息

  @RequestMapping(value="/checkToken",method=RequestMethod.POST)
  public String  responseEvent(HttpServletRequest req, HttpServletResponse resp) {
      String message = "success";
      try {
          //把微信返回的xml信息转义成map
          Map<String, String> map = XmlUtil.xmlToMap(req);
          System.out.println("微信接收到的消息为:"+map.toString());
          String openId = map.get("FromUserName");//消息来源用户标识
          String toUserName = map.get("ToUserName");//消息目的用户标识
          String msgType = map.get("MsgType");//消息类型(event或者text)
          String EventKey = map.get("EventKey");//消息来源用户标识
          if(EventKey.contains("_")){ //scene_id首次关注会有前缀，去掉就和生成二维码时带的一致了
            EventKey = EventKey.split("_")[1];
          }
          String scene_Id = EventKey;
          String eventType = map.get("Event");//事件类型
          if("subscribe".equals(eventType) || "SCAN".equals(eventType) ){ //关注  or 浏览
            //获取缓存的最新的公众号 token
            PcAccessToken token = accessTokenService.findPcToken("");
            String USER_INFO_URL = "https://api.weixin.qq.com/cgi-bin/user/info?access_token=ACCESS_TOKEN&openid=OPENID&lang=zh_CN";
            USER_INFO_URL = USER_INFO_URL.replace("ACCESS_TOKEN", token.getAccessToken());
            USER_INFO_URL = USER_INFO_URL.replace("OPENID", openId);
            String info = HttpUtil.getRequest(USER_INFO_URL);
            System.out.println("----user-----"+info);
            JSONObject obj = JSONObject.fromObject(info);
            String unionid = obj.getString("unionid");
            String nickname = obj.getString("nickname");
            String headimgurl = obj.getString("headimgurl");
            String city = obj.getString("city");
            String province = obj.getString("province");
            String qr_scene = obj.getString("qr_scene");
            //获取到用户信息后处理登录逻辑，比如保存用户信息，用户表scene_id 字段，保存二维码的scend_id，供前端查询用户登录情况。
          }
      } catch (Exception e) {
          e.printStackTrace();
      }
      return message;
  }

xml转Map工具类 

import java.io.IOException;
import java.io.InputStream;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import javax.servlet.http.HttpServletRequest;
import org.dom4j.Document;
import org.dom4j.DocumentException;
import org.dom4j.Element;
import org.dom4j.io.SAXReader;
public class XmlUtil {
	/*
	 * xml转map
	 */
	public static Map<String, String> xmlToMap(HttpServletRequest request) throws IOException, DocumentException{
		HashMap<String, String> map = new HashMap<String,String>();
		SAXReader reader = new SAXReader();
 
		InputStream ins = request.getInputStream();
		Document doc = reader.read(ins);
 
		Element root = doc.getRootElement();
		@SuppressWarnings("unchecked")
		List<Element> list = (List<Element>)root.elements();
 
		for(Element e:list){
			map.put(e.getName(), e.getText());
		}
		ins.close();
		return map;
	}
}