The Spring HandlerInterceptor interface

Spring's request handling mapping mechanism includes the ability to intercept requests by using handler interceptors. These interceptors are used to apply some type of functionality to the requests as in our example of checking whether a user is in session. The interceptors must implement the HandlerInterceptor interface from the org.springframework.web.servlet package where it is possible to apply the functionality in the following three ways:

• Before the handler method is executed by implementing the preHandle method

• After the handler method is executed by implementing the postHandle method

• After the complete request has finished execution by implementing the afterCompletion method

The HandlerInterceptorAdapter abstract class, along with the predefined empty implementations for each method, is normally used to implement custom handlers. Our UserInSessionInterceptor class is defined as follows:

package com.gieman.tttracker.web;

import com.gieman.tttracker...