How to Implement Unified Login Validation in Spring Boot with AOP and Interceptors

Introduction explains the need for unified user login permission verification in Spring Boot projects, replacing repetitive session checks in each controller method.

First, the article shows a basic implementation where each endpoint manually checks HttpSession, highlighting drawbacks such as code duplication and maintenance overhead.

It then proposes using Spring AOP with a @Aspect to create a pre‑handle or around advice, but notes issues: inability to obtain HttpSession and difficulty excluding login/registration endpoints.

To solve this, the tutorial introduces Spring MVC HandlerInterceptor. It provides a custom LoginInterceptor implementing preHandle to verify the session and return HTTP 401 when unauthorized.

The interceptor is registered via a WebMvcConfigurer implementation, adding it to all paths and excluding specific URLs (e.g., /user/login, /user/reg). Alternative registration methods using new LoginInterceptor() are also shown.

Source code excerpts illustrate the interceptor, configuration, and how the DispatcherServlet invokes applyPreHandle before controller execution, linking the interceptor into the request processing chain.

Next, the article covers unified exception handling with @ControllerAdvice and @ExceptionHandler, returning a consistent JSON structure containing code, msg, and data for generic and specific exceptions.

It also discusses unified response formatting using ResponseBodyAdvice or a custom AjaxResult class, showing how to wrap all controller return values into a standard JSON payload and handle special cases for String responses.

Finally, the tutorial provides the AjaxResult utility class with success and fail methods, demonstrating how developers can consistently format API responses throughout the application.