Developing Applications with Tomcat

The Actual Development Process

The following sections highlight the commands and tasks that you, as the developer of the code, will perform. The same basic approach works when you have multiple programmers involved, as long as you have an appropriate source code control system and internal team rules about who is working on what parts of the application at any given time.

Create Project Source Directory

The first step is to create a new project source directory, and customize the build.xml and build script you will be using. The directory structure is described in the section labeled Source Organization, or you can use the sample application located in doc/appdev as a starting point.

Configure Tomcat to Recognize Your Application

In order for Tomcat to recognize your application, you must integrate it as described in the section labeled Integration with Tomcat. Any of the proposed techniques can be used. For our purposes, we will assume that you are using the first approach (unpacked hierarchy), because we set the deployment home to be an appropriate directory under the %TOMCAT_HOME%/webapps directory.

Editing the Source and Building the Web Application

One may make changes to any of the source files (java, html, scripts, etc) and once saved we are ready to build our web application. We compile the application by issuing the build command from the project source root directory. The Ant tool will be utilized to compile any new or updated Java code.

We do this once we have ensured that the following variables have been set:

The JAVA_HOME points at the base directory where you have installed the JDK (for example, c:\jdk1.2.2).
The TOMCAT_HOME points at the base directory where you have installed Tomcat (for example, c:\jakarta-tomcat).

And the following have been done.

You have added directory %JAVA_HOME%/bin to your PATH environment variable, so that the java command is recognized and executed.
Normally, any changes required to the CLASSPATH environment variable are handled for you by the development scripts. However, if you are defining your own scripts, you may need to add file %JAVA_HOME%/lib/tools.jar to your CLASSPATH.

Test Your Web Application

To test your application, you will want to execute it under Tomcat. Assuming you have integrated your application as described earlier, this is very simple. Under Windows, execute:

%TOMCAT_HOME%\bin\startup

This command starts Tomcat as a background process. Now, point your web browser at the home page for your application, by opening the following URL (where "/myapp" is the context path you have assigned to it):

http://localhost:8080/myapp

Now, you can test your application to verify that it operates correctly. When you discover something that needs to change, fix it as follows:

To change a JSP page, modify it in the source directory and then re-execute the build script. The updated page will be recopied, and Tomcat will recognize this the next time that page is accessed -- the page will then be recompiled automatically.
Changing a servlet or other Java class is similar, but the effort required depends on whether you selected the "autoreload" attribute for this context when you integrated with Tomcat. First, edit the file in its source directory, and re-execute the build script. The updated Java class will be recompiled. If autoreloading is selected, Tomcat will notice this change the next time this class is referenced, and will automatically unload and reload your application. Otherwise, you will need to manually stop and restart Tomcat before continuing.

Do not forget to commit your changes to the source code repository when you have completed your testing!

Deploy Your Web Application

When you are through adding new functionality, and you've tested everything, it is time to create the distributable version of your web application that can be deployed on the production server. The following general steps are required:

Issue the command build all from the project source directory, to rebuild everything from scratch one last time.
Issue the command build dist to create a distributable web application archive (WAR) file, as well as a JAR file containing the corresponding source code.
Give the WAR file to the system administrator of your production server environment, so that he or she can install it.

NB. The batch files found in %TOMCAT_HOME%\bin have been written and tested under Windows NT. Some modifications may be necessary for operation on a Windows 98 platform.

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