5.1.1. Creating a directory structure

Suppose we want tomcat to be able to execute the getDateAndTime servlet that was given earlier. Although we could add the files for our own servlets to the examples directory, suppose we want to store our servlets in a separate directory. Suppose this directory is called mytomcat.

We will need to create the mytomcat directory as a subdirectory of:

%CATALINA_HOME%\webapps

We actually have to create a directory tree like this:

webapps
   mytomcat
      WEB-INF
         classes
         lib

You can do this in Windows Explorer, or execute the following commands in a Command Prompt window:

0034:    cd %CATALINA_HOME%\webapps
0035:    mkdir mytomcat
0036:    cd mytomcat
0037:    mkdir WEB-INF
0038:    cd WEB-INF
0039:    mkdir classes lib

5.1.2. Storing the source code of the servlet

We now need somewhere to store the servlet's source code. Although tomcat does not require the source code of a servlet to be stored in the %CATALINA_HOME% directory tree, one possibility is to create a subdirectory of:

%CATALINA_HOME%\webapps\mytomcat

called getDateAndTime and store the text of the getDateAndTime servlet in the file:

%CATALINA_HOME%\webapps\mytomcat\getDateAndTime\getDateAndTime.java

5.1.3. Compiling the code of the servlet

Then execute the following commands from a Command Prompt window:

0040: cd %CATALINA_HOME%\webapps\mytomcat\getDateAndTime
0041: set classpath=..\..\..\common\lib\servlet.jar;.
0042: javac -d ..\WEB-INF\classes getDateAndTime.java
0043: dir /od ..\WEB-INF\classes

This will compile the file getDateAndTime.java. The -d option will arrange for the .class file to be put into a directory where tomcat will find it. So this javac command creates the file:

%CATALINA_HOME%\webapps\mytomcat\WEB-INF\classes\getDateAndTime.class

5.1.4. Getting tomcat to recognise the servlet

By convention, a servlet is accessed using a URL like:

http://localhost:8080/mytomcat/servlet/getDateAndTime

When it gets a URL like this, tomcat knows from the first part of the URL that the files are in:

%CATALINA_HOME%\webapps\mytomcat

However, we have to tell tomcat that there is a servlet called getDateAndTime. We can do this by putting the following text into a file called web.xml in the:

%CATALINA_HOME%\webapps\mytomcat\WEB-INF

directory:

0044: <?xml version="1.0" encoding="ISO-8859-1"?>
0045: <!DOCTYPE web-app
0046:       PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.2//EN"
0047:       "http://java.sun.com/j2ee/dtds/web-app_2.2.dtd">
0048: <web-app>
0049:    <display-name>mytomcat</display-name>
0050:    <servlet>
0051:       <servlet-name>getDateAndTime</servlet-name>
0052:       <display-name>getDateAndTime Servlet</display-name>
0053:       <servlet-class>
0054:          getDateAndTime
0055:       </servlet-class>
0056:    </servlet>
0057:    <servlet-mapping>
0058:       <servlet-name>getDateAndTime</servlet-name>
0059:       <url-pattern>/servlet/getDateAndTime</url-pattern>
0060:    </servlet-mapping>
0061: </web-app>

5.1.5. Executing the servlet

Having done that, restart tomcat, and then use a browser to go to:
http://localhost:8080/mytomcat/servlet/getDateAndTime
This will get tomcat to execute the bytecodes of the file:

%CATALINA_HOME%\webapps\mytomcat\WEB-INF\classes\getDateAndTime.class

5.1.6. Automatically reloading an altered class

If you now alter the text of the servlet getDateAndTime.java, and recompile it placing the file getDateAndTime.class in the classes directory, you will find that this new version will not be executed unless you restart tomcat.

If you wish, you can alter the configuration of tomcat so that it frequently looks at the modification time of .class files in all of the classes directories and reloads its copy of any .class files that have been updated. This can be done by altering the file:

%CATALINA_HOME%\conf\server.xml

adding the line:

0062:            <DefaultContext debug="0" reloadable="true"/>

between the line:

0063:            </Context>

and the line:

0064:       </Host>

You will have to restart tomcat for this change to server.xml to have any effect.