请写出Java的SpringCloud微信登录后端代码和uniapp的微信小程序的微信登录前端代码以及基于mybatis的mapper.xml问价和

由于微信登录需要用到微信开发平台的API，这里只提供代码框架，具体实现需要结合微信开发平台文档进行编写。

Java的SpringCloud微信登录后端代码：

@RestController
@RequestMapping("/wechat")
public class WechatLoginController {
    
    @GetMapping("/login")
    public String wechatLogin() {
        // 生成state参数，防止CSRF攻击
        String state = UUID.randomUUID().toString().replaceAll("-", "");
        // 将state参数保存到session中
        request.getSession().setAttribute("state", state);

        // 构造微信登录授权url
        String redirectUri = URLEncoder.encode("http://yourdomain.com/wechat/callback", "UTF-8");
        String scope = "snsapi_userinfo";
        String appId = "your_app_id";
        String wechatLoginUrl = "https://open.weixin.qq.com/connect/oauth2/authorize?appid=" + appId + "&redirect_uri=" + redirectUri + "&response_type=code&scope=" + scope + "&state=" + state + "#wechat_redirect";

        // 重定向到微信登录授权url
        return "redirect:" + wechatLoginUrl;
    }
    
    @GetMapping("/callback")
    public String wechatCallback(@RequestParam("code") String code, @RequestParam("state") String state, HttpServletRequest request) {
        // 获取session中保存的state参数
        String sessionState = (String) request.getSession().getAttribute("state");
        if (!state.equals(sessionState)) {
            // state参数不一致，可能是CSRF攻击
            return "error";
        }

        // 根据code获取access_token和openid
        String appId = "your_app_id";
        String appSecret = "your_app_secret";
        String accessTokenUrl = "https://api.weixin.qq.com/sns/oauth2/access_token?appid=" + appId + "&secret=" + appSecret + "&code=" + code + "&grant_type=authorization_code";
        String result = HttpUtil.get(accessTokenUrl);
        JSONObject jsonObject = JSON.parseObject(result);
        String accessToken = jsonObject.getString("access_token");
        String openid = jsonObject.getString("openid");

        // 根据access_token和openid获取用户信息
        String userInfoUrl = "https://api.weixin.qq.com/sns/userinfo?access_token=" + accessToken + "&openid=" + openid + "&lang=zh_CN";
        result = HttpUtil.get(userInfoUrl);
        jsonObject = JSON.parseObject(result);
        String nickname = jsonObject.getString("nickname");
        String avatar = jsonObject.getString("headimgurl");

        // 将用户信息保存到数据库中
        // ...

        // 生成jwt token并返回前端
        String token = generateToken(openid);
        return token;
    }
    
    private String generateToken(String openid) {
        // 生成jwt token
        // ...
        return token;
    }
}

uniapp的微信小程序的微信登录前端代码：

<template>
  <view>
    <button type="primary" @click="wechatLogin">微信登录</button>
  </view>
</template>

<script>
export default {
  methods: {
    wechatLogin() {
      wx.login({
        success(res) {
          if (res.code) {
            // 向后端发送请求，获取jwt token
            uni.request({
              url: 'http://yourdomain.com/wechat/callback',
              data: {
                code: res.code
              },
              success(res) {
                console.log(res.data);
                // 将jwt token保存到本地存储中
                uni.setStorageSync('token', res.data);
              }
            });
          } else {
            console.log('登录失败！' + res.errMsg);
          }
        }
      });
    }
  }
}
</script>

基于mybatis的mapper.xml文件：

<mapper namespace="com.example.mapper.UserMapper">

    <resultMap id="userMap" type="com.example.entity.User">
        <id property="id" column="id" />
        <result property="openid" column="openid" />
        <result property="nickname" column="nickname" />
        <result property="avatar" column="avatar" />
    </resultMap>

    <select id="findByOpenid" resultMap="userMap">
        SELECT id, openid, nickname, avatar
        FROM user
        WHERE openid = #{openid}
    </select>

    <insert id="insert" parameterType="com.example.entity.User">
        INSERT INTO user(openid, nickname, avatar)
        VALUES (#{openid}, #{nickname}, #{avatar})
    </insert>

</mapper>