Examples of Spring MVC – HandlerInterceptor Methods
1. preHandle() Method
preHandle() is called by the interceptor before it processes a request, as the name implies. Defaulting to returning true, this function forwards the request to the handler method.
Java
@Overridepublic boolean preHandle( HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception { if (!isAuthenticated(request)) { response.sendRedirect("/login"); return false; // It will reject the request if it is not authenticated } return true; } |
2. postHandle() Method
The interceptor calls this procedure before the DispatcherServlet renders the view, but after the handler has completed its execution. It might be applied to provide ModelAndView more features. There would also be a use case for calculating the processing time of the request.
Java
@Overridepublic void postHandle( HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception { response.setHeader("Cache-Control", "max-age=3600"); //Cache responses for an hour } |
3. afterCompletion() Method
Following the completion of the whole request and the generation of the view, afterCompletion() is called. We can use this technique to get request and response data:
Java
@Overridepublic void afterCompletion( HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception { long duration = System.currentTimeSecond() - request.getStartTime(); log.info("Request completed in {}s", duration); } |
Spring MVC – HandlerInterceptor
Spring interceptor is functional, so let’s take a step back and examine the handler mapping. The HandlerInterceptor interface is a handy class offered by Spring. We may override only the relevant methods out of the three by extending this. The HandlerInterceptor interface is implemented by the HandlerInterceptor class, or it can be extended by the Spring Interceptor class.