Byron Kiourtzoglou

About Byron Kiourtzoglou

Byron is a master software engineer working in the IT and Telecom domains. He is always fascinated by SOA, middleware services and mobile development. Byron is co-founder and Executive Editor at Java Code Geeks.

Spring MVC interceptor example

The demonstration code shows you how to modify the incoming HttpServletRequest object before it reaches your controller. This does nothing more than add a simple string to the request.

public class RequestInitializeInterceptor extends HandlerInterceptorAdapter {
 
  // Obtain a suitable logger.
  private static Log logger = LogFactory

.getLog(RequestInitializeInterceptor.class);
 
  /**
   * In this case intercept the request BEFORE it reaches the controller
   */
  @Override
  public boolean preHandle(HttpServletRequest request,

HttpServletResponse response, Object handler) throws Exception {
    try {
 

logger.info("Intercepting: " + request.getRequestURI());
 

// Do some changes to the incoming request object

updateRequest(request);
 

return true;
    } catch (SystemException e) {

logger.info("request update failed");

return false;
    }
  }
 
  /**
   * The data added to the request would most likely come from a database
   */
  private void updateRequest(HttpServletRequest request) {
 
    logger.info("Updating request object");
    request.setAttribute("commonData",

  "This string is required in every request");
  }
 
  /** This could be any exception */
  private class SystemException extends RuntimeException {
 
    private static final long serialVersionUID = 1L;
    // Blank
  }
}

The next step in implementing an interceptor is, as always, to add something to the Spring XML config file:

<!-- Configures Handler Interceptors --> 
<mvc:interceptors>  
 <!-- This bit of XML will intercept all URLs - which is what you want in a web app -->
 <bean class="marin.interceptor.RequestInitializeInterceptor" />
 
 <!-- This bit of XML will apply certain URLs to certain interceptors -->
 <!-- 
 <mvc:interceptor>
  <mvc:mapping path="/gb/shop/**"/>
  <bean class="marin.interceptor.RequestInitializeInterceptor" />
 </mvc:interceptor>
  -->
</mvc:interceptors>

The XML above demonstrates an either/or choice of adding an interceptor to all request URLs, or if you look at the commented out section, adding an interceptor to specific request URLs, allowing you to choose which URLs are connected to your interceptor class.

Related Article:

Reference: Using Spring Interceptors in your MVC Webapp from our JCG partner Roger Hughes at the Captain Debug’s blog

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