相比微信只需一步就可以通过code换取到openid，qq登录的openid获取流程需要分为2步

一、获取用户的token

先使用授权码code换取到token

String token = getToken(code, qqConfig);

private String getToken(String code, QQConfig qqConfig) {
    String url = "https://graph.qq.com/oauth2.0/token?grant_type=authorization_code&client_id=" +
            qqConfig.getAppId() +
            "&client_secret=" +
            qqConfig.getSecret() +
            "&code=" +
            code +
            "&redirect_uri=" +
            redirectUri;
    String result = restTemplate.getForObject(url, String.class);
    String token = getParams(result).get("access_token");
    if (!StringUtils.hasLength(token)) {
        throw new ServiceException("登录失效");
    }
    return token;
}

private static final String URL_PARTITION = "&";

public static Map<String, String> getParams(String url) {
    Map<String, String> params = new HashMap<>(16);
    try {
        String[] urlParts = url.split("?");
        String query = urlParts[urlParts.length - 1];
        for (String param : query.split(URL_PARTITION)) {
            String[] pair = param.split("=");
            String key = URLDecoder.decode(pair[0], StandardCharsets.UTF_8);
            String value = "";
            if (pair.length > 1) {
                value = URLDecoder.decode(pair[1], StandardCharsets.UTF_8);
            }
            params.put(key, value);
        }
    } catch (Exception e) {
        e.printStackTrace();
    }
    return params;
}

在请求服务器获取token时，服务器的返回值不是json格式的，无法直接转换为对象，这里使用getParams方法来获取我们需要的参数access_token

二、通过token获取openid

public QQAuthResp qqLogin(String token) {
    String url = "https://graph.qq.com/oauth2.0/me?access_token=" +
            token;
    String result = restTemplate.getForObject(url, String.class);
    int start = result.indexOf("{");
    int end = result.lastIndexOf("}") + 1;
    result = result.substring(start, end);
    QQAuthResp userResp = JSONObject.parseObject(result, QQAuthResp.class);

    return userResp;
}

public class QQAuthResp {
    @JSONField(name = "client_id")
    private String clientId;
    private String openid;

}

有了token之后，调用获取用户信息的接口可以获取到openid