What can be operated within HandlerInterceptor? What methods are available?

In Java, particularly in the Spring Framework, HandlerInterceptor allows intercepting HTTP requests at the controller level and performing additional logic.

Main methods of the HandlerInterceptor interface:

• boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) — called before the controller processes the request. You can check conditions, authorization, modify the request, or abort processing by returning false.

• void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) — called after the controller has processed the request but before the view is rendered. You can modify the model or add attributes.

• void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) — called after the entire request processing is complete, including rendering. Used for resource cleanup, logging.

Thus, in HandlerInterceptor, you can operate on the request, response, handler object, and model, manage the processing flow, and perform additional actions at different stages of the HTTP request lifecycle.