In any modern web app, you probably want to have really cool and simple URLs like how WordPress does for your permalinks. E.g., the permalink for this posting is
http://bobobobo.wordpress.com/2008/05/04/how-do-i-design-a-simple-front-controller/
MUCH better than the typical MSDN type urls:
http://msdn.microsoft.com/en-us/library/52cs05fz.aspx
http://msdn.microsoft.com/en-us/library/d06h2x6e.aspx
http://msdn.microsoft.com/en-us/library/bb385954.aspx
Do you think when I complete this posting and publish it, WordPress will ACTUALLY PUT A FILE at http://bobobobo.wordpress.com/2008/05/04/how-do-i-design-a-simple-front-controller/?
NO you dummy!!
Anytime you see REALLY simple urls like http://www.website.com/PersonsUsername/ most likely what is happening there is the web application is using something called REQUEST MAPPING. You do REQUEST MAPPING using what is called a FRONT CONTROLLER.
The FRONT CONTROLLER works to INTERPRET requests for specific URI’s AS requests to OTHER pages, engines, and so on.
Give this a watch.
First, NOTICE how simple that uri is? In case you didn’t follow the link through, its http://cakephp.org/screencasts/view/3.
So CakePHP a front controller to do “request mapping!” WATCH THE VIDEO to get an idea, dude.
ANYWAY, how do you create a really simple front-controller and do request mapping from a Java servlet?
Just create a regular servlet, then make the web.xml entry for it something like this:
<servlet> <servlet-name>member</servlet-name> <servlet-class>member</servlet-class> </servlet> <servlet-mapping> <servlet-name>member</servlet-name> <url-pattern>/member/*</url-pattern> </servlet-mapping>
NOTICE the /member/* for the <url-pattern>? THAT means that ANY requests that come in with the pattern http://www.my.server.com/member/WHATEVER will AUTOMATICALLY be mapped down into the “member” servlet.
So the “member” servlet class might look something like this:
public class member extends HttpServlet
{
protected void doGet( HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
{
String requestURI = request.getRequestURI(); // if the user hit
// http://www.my.site.com/member/BOB then the REQUEST URI looks like
// /member/BOB
// All I'm going to do now is get everything after the last slash,
// and that is what will tell me which member profile is desired:
String desiredUserProfile = requestURI.substring( requestURI.lastIndexOf("/") + 1 );
// work with desiredUserProfile to produce page output, whatever.
}
}
Get the idea?
See also:
Java:
http://java.sun.com/blueprints/corej2eepatterns/Patterns/FrontController.html
PHP:
http://www.phpwact.org/pattern/front_controller
Apache Server:
