• 微信登录之前还需要了解OAuth2知识
• 前期准备
  • 注册微信开放平台
  • 邮箱激活
  • 完善开发者资料（暂不支持个体用户）
  • 开发者资质认证：营业执照、1-2个工作如审批、300元
  • 网站应用：最好是已经部署到服务器上的项目，7个工作日审批
• 审核通过之后会有AppID和AppSecret两个值
  • AppID: 申请的ID
  • AppSecret: 申请的Secret
• 说明：微信登录二维码是以弹出层的形式打开，所以前端需要做一些引入
  • 在页面中引入js文件：https://res.wx.qq.com/connect/zh_CN/htmledition/js/wxLogin.js
  • 在需要使用微信登录的地方实例js对象

var obj = new WxLogin(
        {
          self_redirect: true,
          id: "放置二维码的容器id",
          appid: "",
          scope: "",
          redirect_uri: "",
          state: "",
          style: "",
          href: ""
        }
);

• 整个过程
  • 通过调用后端的接口，将上面js对象所需要的参数返回给前端页面
  • 前端页面获取到所需要的参数即可生成二维码
  • 用户扫描二维码重定向（回调）到当前后端返回的redirect_uri
  • 回调成功则微信登录成功
• 从这个过程中发现微信登录过程中至少需要两个接口
• SpringBoot实现
  • application.properties添加微信登录的一些配置，其中redirect_uri应该是在申请微信登录的时候会存在一个映射关系（这里博主也不是很懂），
    目前微信登录支持localhost，端口应该是申请微信登录账号时设定了（博主觉得是在申请的时候天的回调地址端口有关(狗头)），后面的映射路径就是回调接口的映射路径

wx.open.app_id=上面提供的AppID
wx.open.app_secret=上面提供的AppSecret
wx.open.redirect_uri=http://localhost:8160/api/user/wx/callback
web.base_url=http://localhost:3000

• 新建常量类，读取配置文件中微信的配置信息

import org.springframework.beans.factory.InitializingBean;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;

@Component
public class WxConstantProperties implements InitializingBean {
    @Value("${wx.open.app_id}")
    private String appId;
    @Value("${wx.open.app_secret}")
    private String appSecret;
    @Value("${wx.open.redirect_uri}")
    private String redirectUri;
    @Value("${web.base_url}")
    private String webBaseUrl;

    public static String WX_OPEN_APP_ID;
    public static String WX_OPEN_APP_SECRET;
    public static String WX_OPEN_REDIRECT_URL;
    public static String WEB_BASE_URL;

    @Override
    public void afterPropertiesSet() throws Exception {
        WX_OPEN_APP_ID = appId;
        WX_OPEN_APP_SECRET = appSecret;
        WX_OPEN_REDIRECT_URI = redirectUri;
        WEB_BASE_URL = webBaseUrl;
    }
}

• 第一个接口：返回前端生成二维码的参数

import java.util.HashMap;

@Controller
@RequestMapping("/api/user/wx")
public class WxApiController {

    @GetMapper("/getWxParam")
    @ResponseBody
    public Result<Map<String, Object>> getParam() {
        try {
            Map<String, Object> map = new HashMap<>();
            map.put("appid", WxConstantProperties.WX_OPEN_APP_ID);
            // 固定值
            map.put("scope", "snsapi_login");
            String wxOpenRedirectUri = WxConstantProperties.WX_OPEN_REDIRECT_URI;
            // 应微信开放平台要求，需要使用URLEncoder规范url
            wxOpenRedirectUri = URLEncoder.encode(wxOpenRedirectUri, "utf-8");
            map.put("redirect_uri", wxOpenRedirectUri);
            // 随意值
            map.put("state", System.currentTimeMillis() + "");
            return Result.ok(map);
        } catch (Exception e) {
            e.printStackTrace();
            return Result.fail();
        }
    }
}

• 前端创建两个文件
  • 请求后端接口的js文件

import request from '@/utils/request'
export default {
    getWxParam() {
        return request({
            url: `/api/user/wx/getWxParam`,
            method: 'get'
        })
    }
}

• 当前登录页面的vue组件

<template></template>
<script>
<!-- 引入上面的js文件 -->
import wxApi from '@/api/wx/wxApi.js'
export default {
  data() {
    return {}
  },
  mounted() {
    // 注册全局登录事件对象
    window.loginEvent = new Vue();
    // (注册)监听登录事件
    loginEvent.$on('loginDialogEvent', function () {
      document.getElementById("loginDialog").click();
    })
    // 触发事件，显示登录层：loginEvent.$emit('loginDialogEvent')

    //初始化微信js（包好上面提及的登录js文件）
    const script = document.createElement('script')
    script.type = 'text/javascript'
    script.src = 'https://res.wx.qq.com/connect/zh_CN/htmledition/js/wxLogin.js'
    document.body.appendChild(script)

    // 微信登录回调处理
    let self = this;
    window["loginCallback"] = (name,token, openid) => {
      self.loginCallback(name, token, openid);
    }
  },
  methods: {
    // 第一个接口：获取参数，生成二维码
    wxLogin() {
      // 可以忽略的文本信息
      this.dialogAtrr.showLoginType = 'weixin'

      wxApi.getWxParam().then(response => {
        var obj = new WxLogin({
          self_redirect:true,
          id: 'weixinLogin', // 需要显示的容器id
          appid: response.data.appid, // 公众号appid wx*******
          scope: response.data.scope, // 网页默认即可
          redirect_uri: response.data.redirect_uri, // 授权成功后回调的url
          state: response.data.state, // 可设置为简单的随机数加session用来校验
          style: 'black', // 提供"black"、"white"可选。二维码的样式
          href: '' // 外部css文件url，需要https
        })
      })
    },
    // 第二个接口：重定向到某个页面并保存cookie信息
    loginCallback(name, token, openid) {
      // 打开手机登录层，绑定手机号，改逻辑与手机登录一致
      if(openid != '') {
        this.userInfo.openid = openid

        this.showLogin()
      } else {
        this.setCookies(name, token)
      }
    },
    setCookies(name, token) {
      cookie.set('token', token, { domain: 'localhost' })
      cookie.set('name', name, { domain: 'localhost' })
      window.location.reload()
    },
  }
}
</script>
<style></style>

• 在编写第二个接口前，需要了解一个服务端向另一个服务端发送请求，往往是需要一个工具类

import org.apache.commons.io.IOUtils;
import org.apache.commons.lang.StringUtils;
import org.apache.http.Consts;
import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.NameValuePair;
import org.apache.http.client.HttpClient;
import org.apache.http.client.config.RequestConfig;
import org.apache.http.client.config.RequestConfig.Builder;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.client.methods.HttpRequestBase;
import org.apache.http.conn.ssl.SSLConnectionSocketFactory;
import org.apache.http.conn.ssl.X509HostnameVerifier;
import org.apache.http.entity.ContentType;
import org.apache.http.entity.StringEntity;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.impl.conn.PoolingHttpClientConnectionManager;
import org.apache.http.message.BasicNameValuePair;
import org.apache.http.ssl.SSLContextBuilder;
import org.apache.http.ssl.TrustStrategy;

import javax.net.ssl.SSLContext;
import javax.net.ssl.SSLException;
import javax.net.ssl.SSLSession;
import javax.net.ssl.SSLSocket;
import java.io.IOException;
import java.nio.charset.StandardCharsets;
import java.security.GeneralSecurityException;
import java.security.cert.CertificateException;
import java.security.cert.X509Certificate;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;

public class HttpClientUtils {
    public static final int CONN_TIMEOUT = 10000;
    public static final int READ_TIMEOUT = 10000;
    public static final String CHARSET = "UTF-8";
    public static final String CONTENT_TYPE = "application/x-www-form-urlencoded";
    private static HttpClient client;

    static {
        PoolingHttpClientConnectionManager cm = new PoolingHttpClientConnectionManager();
        cm.setMaxTotal(128);
        cm.setDefaultMaxPerRoute(128);
        client = HttpClients.custom().setConnectionManager(cm).build();
    }

    public static String postParameters(String url, String params) throws Exception {
        return post(url, params, CONTENT_TYPE, CHARSET, CONN_TIMEOUT, READ_TIMEOUT);
    }

    public static String postParameters(String url, String params, String charset, Integer connTimeout, Integer readTimeout) throws Exception {
        return post(url, params, CONTENT_TYPE, charset, connTimeout, readTimeout);
    }

    public static String postParameters(String url, Map<String, String> params) throws Exception {
        return postForm(url, params, null, CONN_TIMEOUT, READ_TIMEOUT);
    }

    public static String postParameters(String url, Map<String, String> params, Integer connTimeout, Integer readTimeout) throws Exception {
        return postForm(url, params, null, connTimeout, readTimeout);
    }

    public static String get(String url) throws Exception {
        return get(url, CHARSET, null, null);
    }

    public static String get(String url, String charset) throws Exception {
        return get(url, charset, CONN_TIMEOUT, READ_TIMEOUT);
    }

    /**
     * 发送一个get请求
     * @param url 请求地址
     * @param charset 字符集编码
     * @param connTimeout 连接超时时间
     * @param readTimeout 响应超时时间
     * @return String
     * @throws Exception ConnectTimeoutException、SocketTimeoutException等其他异常
     */
    public static String get(String url, String charset, Integer connTimeout, Integer readTimeout) throws Exception {
        HttpClient client = null;
        HttpGet get = new HttpGet(url);
        String result = "";
        try {
            // 设置参数
            getHttpRequestBase(get, connTimeout, readTimeout);

            // 获取响应信息
            HttpResponse res = getHttpResponse(url, get, client);

            result = IOUtils.toString(res.getEntity().getContent(), charset);
        }finally {
            get.releaseConnection();
            if (url.startsWith("https") && client instanceof CloseableHttpClient) {
                ((CloseableHttpClient) client).close();
            }
        }
        return result;
    }

    /**
     * 发送一个post请求
     * @param url 请求地址
     * @param body 请求体
     * @param mimeType 类似于Content-Type
     * @param charset 字符集编码
     * @param connTimeout 连接超时时间
     * @param readTimeout 响应超时时间
     * @return String
     * @throws Exception ConnectTimeoutException、SocketTimeoutException等其他异常
     */
    public static String post(String url, String body, String mimeType, String charset, Integer connTimeout, Integer readTimeout) throws Exception {
        HttpClient client = null;
        HttpPost post = new HttpPost(url);
        String result = "";
        try {
            if(!StringUtils.isEmpty(body)) {
                HttpEntity entity = new StringEntity(body, ContentType.create(mimeType, charset));
                post.setEntity(entity);
            }
            // 设置参数
            getHttpRequestBase(post, connTimeout, readTimeout);

            // 获取响应信息
            HttpResponse res = getHttpResponse(url, post, client);

            result = IOUtils.toString(res.getEntity().getContent(), charset);
        } finally {
            post.releaseConnection();
            if (url.startsWith("https") && client instanceof CloseableHttpClient) {
                ((CloseableHttpClient) client).close();
            }
        }
        return result;
    }

    /**
     * form表单提交方式请求
     * @param url 请求地址
     * @param params 表单参数
     * @param headers 请求头
     * @param connTimeout 连接超时时间
     * @param readTimeout 响应超时时间
     * @return String
     * @throws Exception ConnectTimeoutException、SocketTimeoutException等其他异常
     */
    public static String postForm(String url, Map<String, String> params, Map<String, String> headers, Integer connTimeout, Integer readTimeout) throws Exception {
        HttpClient client = null;
        HttpPost post = new HttpPost(url);
        try {
            if (params != null && !params.isEmpty()) {
                List<NameValuePair> formParams = new ArrayList<>();
                Set<Entry<String, String>> entrySet = params.entrySet();
                for (Entry<String, String> entry : entrySet) {
                    formParams.add(new BasicNameValuePair(entry.getKey(), entry.getValue()));
                }
                UrlEncodedFormEntity entity = new UrlEncodedFormEntity(formParams, Consts.UTF_8);
                post.setEntity(entity);
            }
            if (headers != null && !headers.isEmpty()) {
                for (Entry<String, String> entry : headers.entrySet()) {
                    post.addHeader(entry.getKey(), entry.getValue());
                }
            }
            // 设置参数
            getHttpRequestBase(post, connTimeout, readTimeout);

            // 获取响应信息
            HttpResponse res = getHttpResponse(url, post, client);

            return IOUtils.toString(res.getEntity().getContent(), String.valueOf(StandardCharsets.UTF_8));
        }finally {
            post.releaseConnection();
            if (url.startsWith("https") && client instanceof CloseableHttpClient) {
                ((CloseableHttpClient) client).close();
            }
        }
    }

    /**
     * 设置参数
     * @param base 协议请求对象
     * @param connTimeout 连接超时时间
     * @param readTimeout 响应超时时间
     */
    private static void getHttpRequestBase(HttpRequestBase base, Integer connTimeout, Integer readTimeout) {
        Builder customReqConf = RequestConfig.custom();
        if(connTimeout != null) customReqConf.setConnectTimeout(connTimeout);
        if(readTimeout != null) customReqConf.setSocketTimeout(readTimeout);
        base.setConfig(customReqConf.build());
    }

    /**
     * 获取响应信息
     * @param url 请求地址
     * @param base 协议请求对象
     * @return HttpResponse
     * @throws Exception 异常信息
     */
    private static HttpResponse getHttpResponse(String url, HttpRequestBase base, HttpClient client) throws Exception{
        if (url.startsWith("https")) {
            // 执行 Https 请求.
            client = createSSLInsecureClient();
        } else {
            // 执行 Http 请求.
            client = HttpClientUtils.client;
        }
        return client.execute(base);
    }

    /**
     * 创建SSL连接供https协议请求
     * @return CloseableHttpClient
     * @throws GeneralSecurityException 安全异常
     */
    private static CloseableHttpClient createSSLInsecureClient() throws GeneralSecurityException {
        try {
            SSLContext sslContext = new SSLContextBuilder().loadTrustMaterial(null, new TrustStrategy() {
                @Override
                public boolean isTrusted(X509Certificate[] x509Certificates, String s) throws CertificateException {
                    return true;
                }
            }).build();

            SSLConnectionSocketFactory sslConnectionSocketFactory = new SSLConnectionSocketFactory(sslContext, new X509HostnameVerifier() {
                @Override
                public void verify(String s, SSLSocket sslSocket) throws IOException {}

                @Override
                public void verify(String s, X509Certificate x509Certificate) throws SSLException {}

                @Override
                public void verify(String s, String[] strings, String[] strings1) throws SSLException {}

                @Override
                public boolean verify(String s, SSLSession sslSession) {
                    return true;
                }
            });
            return HttpClients.custom().setSSLSocketFactory(sslConnectionSocketFactory).build();
        } catch (GeneralSecurityException e) {
            throw e;
        }
    }

    /**
     * 从 response 里获取 charset
     * @param response  响应信息
     */
    @SuppressWarnings("unused")
    private static String getCharsetFromResponse(HttpResponse response) {
        // Content-Type:text/html; charset=GBK
        if (response.getEntity() != null  && response.getEntity().getContentType() != null && response.getEntity().getContentType().getValue() != null) {
            String contentType = response.getEntity().getContentType().getValue();
            if (contentType.contains("charset=")) {
                return contentType.substring(contentType.indexOf("charset=") + 8);
            }
        }
        return null;
    }
}

• 第二个接口：处理扫码之后的接口（一般是获取当前扫码用户的信息）

@Controller
@RequestMapping("/api/user/wx")
public class WxApiController {
    @GetMapping("/callback")
    public String callback(String code, String state) {
        // 根据临时票据code和微信id及密钥请求微信固定地址，获取两个值（access_token和openid）
        StringBuffer baseAccessTokenUrl = new StringBuffer()
                .append("https://api.weixin.qq.com/sns/oauth2/access_token")
                .append("?appid=%s").append("&secret=%s")
                .append("&code=%s").append("&grant_type=authorization_code");
        String accessTokenUrl = String.format(
                baseAccessTokenUrl.toString(), ConstantWxPropertiesUtils.WX_OPEN_APP_ID,
                ConstantWxPropertiesUtils.WX_OPEN_APP_SECRET, code);
        
        try {
            // 使用HttpClientUtils工具类请求地址
            String accessTokenInfo = HttpClientUtils.get(accessTokenUrl);
            JSONObject jsonObject = JSONObject.parseObject(accessTokenInfo);
            String accessToken = jsonObject.getString("access_token");
            String openid = jsonObject.getString("openid");
            // 如果数据库表中存在openid值，
            UserInfo userInfo = userInfoService.selectWxInfoOpenId(openid);
            if(userInfo == null) {
                // 根据access_token和openid获取扫码人信息
                String baseUserInfoUrl = "https://api.weixin.qq.com/sns/userinfo" +
                        "?access_token=%s" + "&openid=%s";
                String userInfoUrl = String.format(baseUserInfoUrl, accessToken, openid);
                String userInfoResult = HttpClientUtils.get(userInfoUrl);
                JSONObject userObject = JSONObject.parseObject(userInfoResult);
                String nickname = userObject.getString("nickname");
                String headImageUrl = userObject.getString("headimgurl");
                
                // 信息保存到数据库中（省略）
            }
            // 最后重定向到前端某一个页面，期间可以随带一些重要的信息
            return "redirect:" + WxConstantProperties.WEB_BASE_URL + "/weixin/callback?token=" +
                    token + "&openid=" + openid + "&name=" + URLEncoder.encode(name, "utf-8");
        } catch (Exception e) {
            e.printStackTrace();
            return null;
        }
    }
}