微信授权通过code获取openid

做公众号开发时需要获取到用户的openid做唯一标识，微信授权时通过前端调取微信授权接口获取code传给后端，后端拿到code后调取微信接口获取openid，
appid和secret在公众号后台可以查看
/**
 * @param
 * @Description: 获取微信公众号用户登录信息
 * @date
 */
@GetMapping("getInfoByCode")
public JSONObject selectWxUser(String code) {
    JSONObject jsonWxUser = new JSONObject();
    Map map = new HashMap<>();
    String url = "https://api.weixin.qq.com/sns/oauth2/access_token?appid=appid+
            "&secret=" + secret+ "&code=" + code + "&grant_type=authorization_code";
    RestTemplate restTemplate = new RestTemplate();
    String response = restTemplate.getForObject(url, String.class);
    JSONObject jsonObject = JSON.parseObject(response);
    String refresh_token = jsonObject.getString("refresh_token");
    String accessTokenUrl = "https://api.weixin.qq.com/sns/oauth2/refresh_token?appid=" + appid+ "&grant_type=refresh_token&refresh_token=" + refresh_token;
    String responseAccessTokenUrl = restTemplate.getForObject(accessTokenUrl, String.class);
    JSONObject jsonObjectAccessTokenUrl = JSON.parseObject(responseAccessTokenUrl);
    String openid = jsonObjectAccessTokenUrl.getString("openid");
    if (StringUtils.isEmpty(openid)) {
        jsonWxUser.put("code", 201);
        jsonWxUser.put("data", "code已过期");
        return jsonWxUser;
    }

    map.put("openid", openid);
    jsonWxUser.put("code", 200);
    jsonWxUser.put("data", map);
    return jsonWxUser;
}