/**
  * 公眾號微信登錄授權
  */
 @RequestMapping("/wxLogin")
 public void wxLogin(HttpServletResponse response) throws IOException {
  //這個url的域名必須在公眾號中進行注冊驗證，這個地址是成功后的回調地址
  String backUrl = "http://7ca0c439f61c.ngrok.io/callback";//使用自己的域名
  // 第一步：用戶同意授權，獲取code
  //請求地址 snsapi_base snsapi_userinfo
  String url = "https://open.weixin.qq.com/connect/oauth3/authorize" +
    "?appid=" + HttpClientUtil.APPID +
    "&redirect_uri=" + URLEncoder.encode(backUrl,"utf-8") +
    "&response_type=code" +
    "&scope=snsapi_userinfo" +
    "&state=STATE#wechat_redirect";
  logger.info("forward重定向地址{" + url + "}");
  //必須重定向，否則不能成功
  response.sendRedirect(url);
 }

備注：在前端頁面直接加載url 就可以出現二維碼界面了。直接用的微信的頁面，也可以根據自己的愛好進行設計頁面
 /**
  * 公眾號微信登錄授權回調函數
  */
 @RequestMapping("/callback")
 public UserLoginRes callback(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
  UserLoginRes userLoginRes = new UserLoginRes();
  try{
   WXUserInfoReq weixinUserInfo = new WXUserInfoReq();
   /*start 獲取微信用戶基本信息*/
   String code = req.getParameter("code");
   //第二步：通過code換取網頁授權access_token
   String url = "https://api.weixin.qq.com/sns/oauth3/access_token?"
     + "appid=" + HttpClientUtil.APPID
     + "&secret=" + HttpClientUtil.APPSECRET
     + "&code=" + code
     + "&grant_type=authorization_code";
   System.out.println(url);
 
   String result = HttpClientUtil.doGet(url);
   JSONObject jsonObject = JSON.parseObject(result);
 
   /*
   { "access_token":"ACCESS_TOKEN",
   "expires_in":7200,
   "refresh_token":"REFRESH_TOKEN",
   "openid":"OPENID",
   "scope":"SCOPE" 
   }
   */
    String openid = jsonObject.getString("openid");
    String access_token = jsonObject.getString("access_token");
 
   //第三步驗證access_token是否失效；
   String chickUrl = "https://api.weixin.qq.com/sns/auth?access_token="
     + access_token + "&openid=" + openid;
   String resultInfo = HttpClientUtil.doGet(chickUrl);
   JSONObject chickuserInfo = JSON.parseObject(resultInfo);
   System.out.println(chickuserInfo.toString());
   if (!"0".equals(chickuserInfo.getString("errcode"))) {
    String refreshInfo1 = HttpClientUtil.doGet(chickUrl);
    JSONObject refreshInfo = JSON.parseObject(refreshInfo1);
    /*
    { "access_token":"ACCESS_TOKEN",
    "expires_in":7200,
    "refresh_token":"REFRESH_TOKEN",
    "openid":"OPENID",
    "scope":"SCOPE" }
    */
    access_token = refreshInfo.getString("access_token");
   }
 
   // 第四步：拉取用戶信息
   String infoUrl = "https://api.weixin.qq.com/sns/userinfo?access_token=" + access_token
     + "&openid=" + openid
     + "&lang=zh_CN";
   JSONObject userInfo = JSON.parseObject(HttpClientUtil.doGet(infoUrl));
   /*
   { "openid":" OPENID",
   "nickname": NICKNAME,
   "sex":"1",
   "province":"PROVINCE"
   "city":"CITY",
   "country":"COUNTRY",
   "headimgurl": "http://wx.qlogo.cn/mmopen/g3MonUZtNHkdmzicIlibx6iaFqAc56vxLSUfpb6n5WKSYVY0ChQKkiaJSgQ1dZuTOgvLLrhJbERQQ4eMsv84eavHiaiceqxibJxCfHe/46",
   "privilege":[ "PRIVILEGE1" "PRIVILEGE2"  ],
   "unionid": "o6_bmasdasdsad6_2sgVt7hMZOPfL"
   }
   */
   System.out.println(userInfo.getString("openid") + ":" + userInfo.getString("nickname") +":" + userInfo.getString("sex"));
  }catch (Exception e){
   e.printStackTrace();
   userLoginRes.setResult("NO");
   userLoginRes.setRtnErrId("ERROR");
   userLoginRes.setRtnErrMsg(e.getMessage());
  }
  return userLoginRes;
 }

public class HttpClientUtil {
 //appid、secret為自己公眾號平臺的appid和secret
 public static final String APPID="xxxxxxx";
 public static final String APPSECRET ="xxxxxxx"; 
 
 public static String doGet(String url, Map<String, String> param) {
  // 創建Httpclient對象
  CloseableHttpClient httpclient = HttpClients.createDefault();
 
  String resultString = "";
  CloseableHttpResponse response = null;
  HttpGet httpGet = null;
  try {
   // 創建uri
   URIBuilder builder = new URIBuilder(url);
   if (param != null) {
    for (String key : param.keySet()) {
     builder.addParameter(key, param.get(key));
    }
   }
   URI uri = builder.build();
   // 創建http GET請求
   httpGet = new HttpGet(uri);
   httpGet.setHeader("Host", "api.weixin.qq.com");
   httpGet.setHeader("User-Agent", "Mozilla/5.0 (Windows NT 6.1; WOW64; Trident/7.0; rv:11.0) like Gecko");
   httpGet.setHeader("Accept", "text/html, application/xhtml+xml, */*");
   httpGet.setHeader("Accept-Encoding", "gzip, deflate, br");
   httpGet.setHeader("Connection", "keep-alive");
   httpGet.setHeader("Accept-Language", "zh-CN");
   httpGet.setHeader("Cache-Control", "no-cache");
 
   // 執行請求
   response = httpclient.execute(httpGet);
   // 判斷返回狀態是否為200
   if (response.getStatusLine().getStatusCode() == 200) {
    resultString = EntityUtils.toString(response.getEntity(), "UTF-8");
   }
  } catch (Exception e) {
   e.printStackTrace();
  } finally {
   try {
    if (response != null) {
     response.close();
    }
    httpGet.releaseConnection();
    httpclient.close();
   } catch (IOException e) {
    e.printStackTrace();
   }
  }
  return resultString;
 }
 
 public static String doGet(String url) {
  return doGet(url, null);
 }
 
 public static String doPost(String url, Map<String, String> param) {
  // 創建Httpclient對象
  CloseableHttpClient httpClient = HttpClients.createDefault();
  CloseableHttpResponse response = null;
  String resultString = "";
  try {
   // 創建Http Post請求
   HttpPost httpPost = new HttpPost(url);
   // 創建參數列表
   if (param != null) {
    List<NameValuePair> paramList = new ArrayList<>();
    for (String key : param.keySet()) {
     paramList.add(new BasicNameValuePair(key, param.get(key)));
    }
    // 模擬表單
    UrlEncodedFormEntity entity = new UrlEncodedFormEntity(paramList);
    httpPost.setEntity(entity);
   }
   // 執行http請求
   response = httpClient.execute(httpPost);
   resultString = EntityUtils.toString(response.getEntity(), "utf-8");
  } catch (Exception e) {
   e.printStackTrace();
  } finally {
   try {
    response.close();
   } catch (IOException e) {
    e.printStackTrace();
   }
  }
 
  return resultString;
 }
 
 public static String doPost(String url) {
  return doPost(url, null);
 }
 
 public static String doPostJson(String url, String json) {
  // 創建Httpclient對象
  CloseableHttpClient httpClient = HttpClients.createDefault();
  CloseableHttpResponse response = null;
  String resultString = "";
  try {
   // 創建Http Post請求
   HttpPost httpPost = new HttpPost(url);
   // 創建請求內容
   StringEntity entity = new StringEntity(json, ContentType.APPLICATION_JSON);
   httpPost.setEntity(entity);
   // 執行http請求
   response = httpClient.execute(httpPost);
   resultString = EntityUtils.toString(response.getEntity(), "utf-8");
  } catch (Exception e) {
   e.printStackTrace();
  } finally {
   try {
    response.close();
   } catch (IOException e) {
    e.printStackTrace();
   }
  }
  return resultString;
 }
 
 public static String doGetStr(String httpurl) {
  HttpURLConnection connection = null;
  InputStream is = null;
  BufferedReader br = null;
  String result = null;// 返回結果字符串
  try {
   // 創建遠程url連接對象
   URL url = new URL(httpurl);
   // 通過遠程url連接對象打開一個連接，強轉成httpURLConnection類
   connection = (HttpURLConnection) url.openConnection();
   // 設置連接方式：get
   connection.setRequestMethod("GET");
   // 設置連接主機服務器的超時時間：15000毫秒
   connection.setConnectTimeout(15000);
   // 設置讀取遠程返回的數據時間：60000毫秒
   connection.setReadTimeout(60000);
   //設置請求頭
   connection.setRequestProperty("Host", "api.weixin.qq.com");
   connection.setRequestProperty("User-Agent", "Mozilla/5.0 (Windows NT 6.1; WOW64; Trident/7.0; rv:11.0) like Gecko");
   connection.setRequestProperty("Accept", "text/html, application/xhtml+xml, */*");
   connection.setRequestProperty("Accept-Encoding", "gzip, deflate, br");
   connection.setRequestProperty("Connection", "keep-alive");
   connection.setRequestProperty("Accept-Language", "zh-CN");
   connection.setRequestProperty("Cache-Control", "no-cache");
 
   // 發送請求
   connection.connect();
   // 通過connection連接，獲取輸入流
   if (connection.getResponseCode() == 200) {
    is = connection.getInputStream();
    // 封裝輸入流is，并指定字符集
    br = new BufferedReader(new InputStreamReader(is, "UTF-8"));
    // 存放數據
    StringBuffer sbf = new StringBuffer();
    String temp = null;
    while ((temp = br.readLine()) != null) {
     sbf.append(temp);
     sbf.append("\r\n");
    }
    result = sbf.toString();
   }
  } catch (MalformedURLException e) {
   e.printStackTrace();
  } catch (IOException e) {
   e.printStackTrace();
  } finally {
   // 關閉資源
   if (null != br) {
    try {
     br.close();
    } catch (IOException e) {
     e.printStackTrace();
    }
   }
   if (null != is) {
    try {
     is.close();
    } catch (IOException e) {
     e.printStackTrace();
    }
   }
   connection.disconnect();// 關閉遠程連接
  }
  return result;
 }
 
}

//3.根據uuid查詢用戶是否存在，如果存在直接登錄。如果不存在則自動注冊，在登錄
   UserInfoModel userInfoByWechat = iUserDao.getUserInfoByWechat(userInfoStr.get("unionid").toString());
   if (userInfoByWechat != null) {
    return ReturnMessage.success(0,"獲取成功",userInfoByWechat);
   }
   //4.數據庫添加用戶信息
   String username = userInfoStr.get("nickname").toString();
   String unionid = userInfoStr.get("unionid").toString();
   UserInfoBean userInfoBean = new UserInfoBean();
   userInfoBean.setUuid(unionid);
   userInfoBean.setUsername(username);
   // 微信登錄
   userInfoBean.setStatus(2);
   iUserDao.insertUser(userInfoBean);
   //5.根據uuid查詢新注冊的用戶信息
   UserInfoModel userInfoModel= iUserDao.getUserInfoByWechat(unionid);
   if (userInfoModel == null) {
    return ReturnMessage.fail(400,"用戶添加失敗，請重新操作");
   }