@RestController
public class UserInfoController {
  @Autowired
  private OAuthService oAuthService;

  @RequestMapping("/userInfo")
  public HttpEntity userInfo(HttpServletRequest request) throws OAuthSystemException {
    try {
      //构建OAuth资源请求
      OAuthAccessResourceRequest oauthRequest = 
            new OAuthAccessResourceRequest(request, ParameterStyle.QUERY);
      //获取Access Token
      String accessToken = oauthRequest.getAccessToken();

      //验证Access Token
      if (!oAuthService.checkAccessToken(accessToken)) {
        // 如果不存在/过期了，返回未验证错误，需重新验证
      OAuthResponse oauthResponse = OAuthRSResponse
              .errorResponse(HttpServletResponse.SC_UNAUTHORIZED)
              .setRealm(Constants.RESOURCE_SERVER_NAME)
              .setError(OAuthError.ResourceResponse.INVALID_TOKEN)
              .buildHeaderMessage();

        HttpHeaders headers = new HttpHeaders();
        headers.add(OAuth.HeaderType.WWW_AUTHENTICATE, 
          oauthResponse.getHeader(OAuth.HeaderType.WWW_AUTHENTICATE));
      return new ResponseEntity(headers, HttpStatus.UNAUTHORIZED);
      }
      //返回用户名
      String username = oAuthService.getUsernameByAccessToken(accessToken);
      return new ResponseEntity(username, HttpStatus.OK);
    } catch (OAuthProblemException e) {
      //检查是否设置了错误码
      String errorCode = e.getError();
      if (OAuthUtils.isEmpty(errorCode)) {
        OAuthResponse oauthResponse = OAuthRSResponse
               .errorResponse(HttpServletResponse.SC_UNAUTHORIZED)
               .setRealm(Constants.RESOURCE_SERVER_NAME)
               .buildHeaderMessage();

        HttpHeaders headers = new HttpHeaders();
        headers.add(OAuth.HeaderType.WWW_AUTHENTICATE, 
          oauthResponse.getHeader(OAuth.HeaderType.WWW_AUTHENTICATE));
        return new ResponseEntity(headers, HttpStatus.UNAUTHORIZED);
      }

      OAuthResponse oauthResponse = OAuthRSResponse
               .errorResponse(HttpServletResponse.SC_UNAUTHORIZED)
               .setRealm(Constants.RESOURCE_SERVER_NAME)
               .setError(e.getError())
               .setErrorDescription(e.getDescription())
               .setErrorUri(e.getUri())
               .buildHeaderMessage();

      HttpHeaders headers = new HttpHeaders();
      headers.add(OAuth.HeaderType.WWW_AUTHENTICATE, 、
        oauthResponse.getHeader(OAuth.HeaderType.WWW_AUTHENTICATE));
      return new ResponseEntity(HttpStatus.BAD_REQUEST);
    }
  }
}