如何使用Java开发一个基于OAuth的身份认证系统

@Controller
public class OAuthController {

    @RequestMapping(value = "/login", method = RequestMethod.GET)
    public String login() {
        return "redirect:/oauth2/authorize?client_id=<your_client_id>&redirect_uri=<your_redirect_uri>&response_type=code&scope=read";
    }

    @RequestMapping(value = "/oauth2/callback", method = RequestMethod.GET)
    public String callback(@RequestParam("code") String code) {
        RestTemplate restTemplate = new RestTemplate();
        HttpHeaders headers = new HttpHeaders();
        headers.setContentType(MediaType.APPLICATION_FORM_URLENCODED);

        MultiValueMap<String, String> params = new LinkedMultiValueMap<>();
        params.add("client_id", "<your_client_id>");
        params.add("client_secret", "<your_client_secret>");
        params.add("code", code);
        params.add("grant_type", "authorization_code");
        params.add("redirect_uri", "<your_redirect_uri>");

        HttpEntity<MultiValueMap<String, String>> requestEntity = new HttpEntity<>(params, headers);
        ResponseEntity<AccessTokenResponse> responseEntity = restTemplate.postForEntity("<authorization_server_token_endpoint>", requestEntity, AccessTokenResponse.class);
        AccessTokenResponse accessTokenResponse = responseEntity.getBody();

        // 根据访问令牌获取用户信息
        String userInfoUrl = "<user_info_endpoint>" + "?access_token=" + accessTokenResponse.getAccessToken();
        ResponseEntity<UserInfoResponse> userInfoResponseEntity = restTemplate.getForEntity(userInfoUrl, UserInfoResponse.class);
        UserInfoResponse userInfoResponse = userInfoResponseEntity.getBody();

        // 在这里可以根据用户信息进行身份认证和授权

        return "redirect:/home";
    }
}