Defining Projects in your Apache/Tomcat Intranet Environment Page III

Each web application (that is, each subdirectory under %Tomcat_Home%/webapps should have its own WEB-INF and META-INF subdirectories.  In the WEB-INF subdirectory there is a file called web.xml.  This is the file that defines the servlet and URL mapping for your application.  The relevant parts of web.xml will look as follows for our application:

<?xml version="1.0" encoding="ISO-8859-1"?>

<!DOCTYPE web-app

    PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.2//EN"

    "http://java.sun.com/j2ee/dtds/web-app_2_2.dtd">

<web-app>

    <servlet>

        <servlet-name>

            snoop

        </servlet-name>

        <servlet-class>

            SnoopServlet

        </servlet-class>

</servlet>

    <servlet>

      <servlet-name>

          HelloWorld

      </servlet-name>

      <servlet-class>

          HelloWorldExample

      </servlet-class>

    </servlet>

    <servlet-mapping>

        <servlet-name>

            snoop

        </servlet-name>

        <url-pattern>

            /snoop

        </url-pattern>

    </servlet-mapping>

    <servlet-mapping>

        <servlet-name>

            HelloWorld

        </servlet-name>

        <url-pattern>

            /hello

        </url-pattern>

    </servlet-mapping>

  </web-app>

Without getting into an XML lesson, each application has a <servlet></servlet> element which maps the actual class name to the name you want to call the servlet and a <servlet-mapping></servlet-mapping> element which maps the servlet name you defined in <servlet> to a URL the user will type in.  Let us deconstruct the Snoop example.   Earlier, we defined the mount point as follows:

# This mount point will be used for examples

ApJServMount /examples  /root

This means that anything with http://localhost/examples will map to the root application, which is not very meaningful until we define servlets that correspond to this.  That is what we accomplish with the following code:

<servlet>

        <servlet-name>

            snoop

        </servlet-name>

        <servlet-class>

            SnoopServlet

        </servlet-class>

The above code means that the servlet name of "snoop" corresponds to a class by the name of "SnoopServlet".  Remember that this class is located within the examples web application (%Tomcat_Home/wepapps/examples/WEB-INF/classes) because we are editing the web.xml within the /examples/WEB-INF subdirectory. 

Next, we define the URL mapping to the servlet as follows:

<servlet-mapping>

        <servlet-name>

            snoop

        </servlet-name>

        <url-pattern>

            /snoop

        </url-pattern>

    </servlet-mapping>

This means that if a user types in /snoop after http://localhost/examples (that is, http://localhost/examples/snoop) it will call the servlet named "snoop" which we know from a paragraph ago corresponds to the SnoopServlet class.

Take a moment and breathe.  At least for me, I know it is a lot to get your head around and it can be very confusing.  However, once you work with it more, you begin to understand how the items within web.xml for each application relate not only to each other but also to the mounting points and the environment as a whole.  If you take these examples and begin to expand upon them in your own environment, it will help you to form a fully functioning, multi-project environment one step at a time.

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