public class LoginInterceptor implements HandlerInterceptor {

  @Override
  public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
  	// 這里是關(guān)鍵
    User loginUser = (User) request.getSession().getAttribute("user");
    if (loginUser == null) {
      // 未登錄拋出異常，交給統(tǒng)一異常處理器處理
      throw new CustomException(ResultCode.USER_NOT_LOGIN);
    }
    return true;
  }

  @Override
  public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {

  }

  @Override
  public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {

  }
}

@Configuration
public class WebMvcConfig implements WebMvcConfigurer {

  @Override
  public void addInterceptors(InterceptorRegistry registry) {
    //注冊TestInterceptor攔截器
    registry.addInterceptor(new LoginInterceptor())
        .addPathPatterns("/**")
        // 排除登錄注冊等接口，注意這里的格式是 /**/xxx
        .excludePathPatterns("/**/login", "/**/register"); 
  }
}

 /**
   * 登錄
   * @return 用戶信息
   */
public User login(UserVO userVO. HttpServlet) {
  String username = userVO.getUsername();
  String password = userVO.getPassword();

  User user = userMapper.findByUsernameAndPassword(username, password);
  // 未找到用戶
  if(user == null) {
    throw new CustomException(ResultCode.USER_ACCOUNT_ERROR);
  }
  // 設置session中的用戶信息
  SessionUtils.setSessionAttribute("user", user);
  return user;
}