Application Developer's Guide

In order to take advantage of the special Ant tasks that interact with the Manager web application, you need to perform the following tasks once (no matter how many web applications you plan to develop).

• Configure the Ant custom tasks. The implementation code for the Ant custom tasks is in a JAR file named $CATALINA_HOME/lib/catalina-ant.jar, which must be copied in to the lib directory of your Ant installation.

• Define one or more Tomcat users. The Manager web application runs under a security constraint that requires a user to be logged in, and have the security role manager-script assigned to then. How such users are defined depends on which Realm you have configured in Tomcat's conf/server.xml file -- see the Realm Configuration How-To for more information. You may define any number of users (with any username and password that you like) with the manager-script role.

The first step is to create a new project source directory, and customize the build.xml and build.properties files you will be using. The directory structure is described in the previous section, or you can use the sample application as a starting point.

Create your project source directory, and define it within your source code control system. This might be done by a series of commands like this:

cd {my home directory}
mkdir myapp <-- Assumed "project source directory"
cd myapp
mkdir docs
mkdir src
mkdir web
mkdir web/WEB-INF
cvs or svn or git ... <-- Add this structure to the appropriate repository

To verify that the project was created correctly in the source code control repository, you may wish to check out the project to a separate directory and confirm that all the expected contents are present.

Next, you will need to create and check in an initial version of the build.xml script to be used for development. For getting started quickly and easily, base your build.xml on the basic build.xml file, included with this manual, or code it from scratch.

cd {my home directory}
cd myapp
emacs build.xml     <-- if you want a real editor :-)
cvs or svn or git ... <-- Add this file to the repository

The next step is to customize the Ant properties that are named in the build.xml script. This is done by creating a file named build.properties in your project's top-level directory. The supported properties are listed in the comments inside the sample build.xml script. At a minimum, you will generally need to define the catalina.home property defining where Tomcat is installed, and the manager application username and password. You might end up with something like this:

# Context path to install this application on
app.path=/hello

# Tomcat installation directory
catalina.home=/usr/local/apache-tomcat-8.5

# Manager webapp username and password
manager.username=myusername
manager.password=mypassword

In general, you will not want to check the build.properties file in to the source code control repository, because it is unique to each developer's environment.

Now, create the initial version of the web application deployment descriptor. You can base web.xml on the basic web.xml file, or code it from scratch.

cd {my home directory}
cd myapp/web/WEB-INF
emacs web.xml
cvs or svn or git ... <-- Add this file to the repository

The edit/build/test tasks will generally be your most common activities during development and maintenance. The following general principles apply. As described in Source Organization, newly created source files should be located in the appropriate subdirectory, under your project source directory.

You should regularly refresh your development directory to reflect the work performed by other developers.

To create a new file, go to the appropriate directory and create the file. When you are satisfied with its contents (after building and testing is successful), add the new file to the repository. For example, to create a new JSP page:

cd {my home directory}
cd myapp/web        <-- Ultimate destination is document root
emacs mypage.jsp
... build and test the application ...
cvs or svn or git ... <-- Add this file to the repository

Java source code that is defined in packages must be organized in a directory hierarchy (under the src/ subdirectory) that matches the package names. For example, a Java class named com.mycompany.mypackage.MyClass.java should be stored in file src/com/mycompany/mypackage/MyClass.java. Whenever you create a new file, don't forget to add it to the source code control system.

To edit an existing source file, you will generally just start editing and testing, then commit the changed file when everything works.

When you are ready to compile the application, issue the following commands (generally, you will want a shell window open that is set to the project source directory, so that only the last command is needed):

cd {my home directory}
cd myapp        <-- Normally leave a window open here
ant

The Ant tool will be execute the default "compile" target in your build.xml file, which will compile any new or updated Java code. If this is the first time you compile after a "build clean", it will cause everything to be recompiled.

To force the recompilation of your entire application, do this instead:

cd {my home directory}
cd myapp
ant all

This is a very good habit immediately before checking in changes, to make sure that you have not introduced any subtle problems that Javac's conditional checking did not catch.

To test your application, you will want to install it under Tomcat. The quickest way to do that is to use the custom Ant tasks that are included in the sample build.xml script. Using these commands might follow a pattern like this:

• Start Tomcat if needed. If Tomcat is not already running, you will need to start it in the usual way.

• Compile your application. Use the ant compile command (or just ant, since this is the default). Make sure that there are no compilation errors.

• Install the application. Use the ant install command. This tells Tomcat to immediately start running your app on the context path defined in the app.path build property. Tomcat does NOT have to be restarted for this to take effect.

• Test the application. Using your browser or other testing tools, test the functionality of your application.

• Modify and rebuild as needed. As you discover that changes are required, make those changes in the original source files, not in the output build directory, and re-issue the ant compile command. This ensures that your changes will be available to be saved (via your chosen source code control system) later on -- the output build directory is deleted and recreated as necessary.

• Reload the application. Tomcat will recognize changes in JSP pages automatically, but it will continue to use the old versions of any servlet or JavaBean classes until the application is reloaded. You can trigger this by executing the ant reload command.

• Remove the application when you are done. When you are through working on this application, you can remove it from live execution by running the ant remove command.

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

When you are through adding new functionality, and you've tested everything (you DO test, don't you :-), 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 ant all from the project source directory, to rebuild everything from scratch one last time.

• Use the source code control system to tag the current state of the code to create an identifier for all of the source files utilized to create this release. This allows you to reliably reconstruct a release (from sources) at a later time.

• Issue the command ant dist to create a distributable web application archive (WAR) file, as well as a JAR file containing the corresponding source code.

• Package the contents of the dist directory using the tar or zip utility, according to the standard release procedures used by your organization.