Defining a HandlerInterceptor

The following are the methods you can override in HandlerInterceptorAdapter:

• public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler): Invoked before the handler method is invoked
• public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView): Invoked after the handler method is invoked
• public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex): Invoked after the request processing is complete

The following example implementation shows how to create a HandlerInterceptor. Let's start with creating a new class that extends HandlerInterceptorAdapter:

    public class HandlerTimeLoggingInterceptor extends 
    HandlerInterceptorAdapter {

The preHandle method is invoked before the handler is called. Let's place an attribute on the request, indicating the start time of handler invocation:

    @Override 
    public boolean preHandle(HttpServletRequest request, 
      HttpServletResponse response, Object handler) throws Exception { 
      request.setAttribute( 
      "startTime", System.currentTimeMillis()); 
      return true; 
    }

The postHandle method is invoked after the handler is called. Let's place an attribute on the request, indicating the end time of the handler invocation:

    @Override 
    public void postHandle(HttpServletRequest request, 
    HttpServletResponse response, Object handler, 
    ModelAndView modelAndView) throws Exception { 
       request.setAttribute( 
       "endTime", System.currentTimeMillis()); 
     }

The afterCompletion method is invoked after the request processing is complete. We will identify the time spent in the handler using the attributes that we set into the request earlier:

    @Override 
    public void afterCompletion(HttpServletRequest request, 
    HttpServletResponse response, Object handler, Exception ex) 
    throws Exception { 
      long startTime = (Long) request.getAttribute("startTime"); 
      long endTime = (Long) request.getAttribute("endTime"); 
      logger.info("Time Spent in Handler in ms : "  
      + (endTime - startTime)); 
    }