SE452: The Deployment Descriptor [2/20]

Last week, we discussed the web application deployment descriptor, and looked at a few examples.

web.xml is an xml document, and the container requires that it not only be well-formed, but valid. It is checked against the DTD or Schema (for Servlets 2.4, optionally). The container should report errors in the web.xml file to the developer in a reasonable format. For Tomcat, this will be in the logs.

All images taken from the Servlet 1.4 specification

The web.xml structure:

The servlet node:

The servlet-mapping node:

The error-page node:

The env-entry node:

A concrete example:

    <?xml version="1.0" encoding="UTF-8"?>

    <!DOCTYPE web-app
    PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"
    "http://java.sun.com/dtd/web-app_2_3.dtd">
    
    <web-app>
        <display-name>A Simple Application</display-name>
        <context-param>
            <param-name>Webmaster</param-name>
            <param-value>webmaster@mycorp.com</param-value>
        </context-param>
        <servlet>
            <servlet-name>catalog</servlet-name>
            <servlet-class>com.mycorp.CatalogServlet</servlet-class>
            <init-param>
                <param-name>catalog</param-name>
                <param-value>Spring</param-value>
            </init-param>
        </servlet>
        <servlet-mapping>
            <servlet-name>catalog</servlet-name>
            <url-pattern>/catalog/*</url-pattern>
        </servlet-mapping>
        <session-config>
            <session-timeout>30</session-timeout>
        </session-config>
        <mime-mapping>
            <extension>pdf</extension>
            <mime-type>application/pdf</mime-type>
        </mime-mapping>
        <welcome-file-list>
            <welcome-file>index.jsp</welcome-file>
            <welcome-file>index.html</welcome-file>
            <welcome-file>index.htm</welcome-file>
        </welcome-file-list>
        <error-page>
            <error-code>404</error-code>
            <location>/404.html</location>
        </error-page>
    </web-app>