Overview of Java Web Technologies, Part 1 - Reviewing Deployment Descriptors (
Page 4 of 9 )
A deployment
descriptor is an XML file, so you can edit it using a text editor. The
deployment descriptor for an application compliant with the Servlet 2.3
specification starts with the following:
<?xml version="1.0"
encoding="ISO-8859-1"?>
<!DOCTYPE web-app PUBLIC "-//Sun Microsystems,
Inc.//DTD Web Application
2.3//EN"
"http://java.sun.com/dtd/web-app_2_3.dtd">
These headers indicate that the document type definition (DTD) for this
deployment descriptor can be downloaded from http://java.sun.com/dtd/web-app_2_3.dtd.
If you open the DTD file, you can see that the root element of a deployment
descriptor is
web-app. The web-app element can have up to 23 kinds of
subelements, as shown here:
<!ELEMENT web-app (icon?,
display-name?, description?, distributable?, context-param*, filter*,
filter-mapping*, listener*, servlet*, servlet-mapping*, session-config?,
mime-mapping*, welcome-file-list?, error-page*, taglib*, resource-env-ref*,
resource-ref*, security-constraint*,login-config?, security-role*, env-entry*,
ejb-ref*, ejb-local-ref*)>
All of these subelements are optional, so you are not required to include any
of them. The subelements preceding a question mark (?) can appear only once.
Those followed by an asterisk (*) can appear many times. Additionally, some of
these subelements can have subelements.
Note that in Servlet 2.4, a deployment descriptor is validated against a
schema, not a DTD file. However, the elements under web-app are pretty much the same.
 Remember: This is
part one of the first chapter of JavaServer Faces Programming, by Budi
Kurniawan (McGraw-Hill/Osborne, ISBN 0-07-222983). Stay tuned for part 2 of
"Overviews of Java Web Technologies," where we learn about JSP, JavaBeans, and
Model 2.
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