Head First Servlets and JSP, 2nd Edition

Servlet mappings can be “fake”

The URL pattern you put into a servlet mapping can be completely made-up. Imaginary. Fake. Just a logical name you want to give clients. Clients who have no business knowing anything about the real physical structure of your web app.

With servlet mappings, you have two structures to organize: the real physical directory and file structure in which your web app resources live, and the virtual/logical structure.

The THREE types of <url-pattern> elements

1. EXACT match

   

2. DIRECTORY match

   

3. EXTENSION match

   

The virtual/logical structure exists simply because you SAY it exists!

The URL patterns in the DD don’t map to anything except other <servlet-name> elements in the DD.

The <servlet-name> elements are the key to servlet mapping—they match a request <url-pattern> to an actual servlet class.

Key point: clients request servlets by <url-pattern>, NOT by <servlet-name> or <servlet-class>!

BE the Container

Which servlet will the Container choose given the DD servlet mappings and the client requests shown? You’ll have questions like this on the real exam!

Key rules about servlet mappings

1) The Container looks for matches in the order shown on the opposite page. In other words, it looks ...