Automate your build process using Java and Ant

Introducing the powerful XML-based scripting tool, Ant

By Michael Cymerman, JavaWorld.com, 10/20/00

A defined process is one of the most necessary but often least-used tools in software development. It is by nature an overhead task that accompanies a development effort. A defined build process ensures that the software in your development project is built in the exact same manner each time a build is executed. As the build process becomes more complex -- for example, with EJB builds or additional tasks -- it becomes more necessary to achieve such standardization. You should establish, document, and automate the exact series of steps as much as possible.

Why do I need a defined build process?

A defined build process is an essential part of any development cycle because it helps close the gap between the development, integration, test, and production environments. A build process alone will speed the migration of software from one environment to another. It also removes many issues related to compilation, classpath, or properties that cost many projects time and money.

What is Ant?

Ant is a platform-independent scripting tool that lets you construct your build scripts in much the same fashion as the "make" tool in C or C++. You can use a large number of built-in tasks in Ant without any customization. Some of the most important tasks are shown in the following table but explained in more detail in the example that follows.

Here are some useful commands that are built in the Ant distribution.

Command	Description
Ant	Used to execute another ant process from within the current one.
Copydir	Used to copy an entire directory.
Copyfile	Used to copy a single file.
Cvs	Handles packages/modules retrieved from a CVS repository.
Delete	Deletes either a single file or all files in a specified directory and its sub-directories.
Deltree	Deletes a directory with all its files and subdirectories.
Exec	Executes a system command. When the os attribute is specified, then the command is only executed when Ant is run on one of the specified operating systems.
Get	Gets a file from an URL.
Jar	Jars a set of files.
Java	Executes a Java class within the running (Ant) VM or forks another VM if specified.
Javac	Compiles a source tree within the running (Ant) VM.
Javadoc/Javadoc2	Generates code documentation using the javadoc tool.
Mkdir	Makes a directory.
Property	Sets a property (by name and value), or set of properties (from file or resource) in the project.
Rmic	Runs the rmic compiler for a certain class.
Tstamp	Sets the DSTAMP, TSTAMP, and TODAY properties in the current project.
Style	Processes a set of documents via XSLT.

While other tools are available for doing software builds, Ant is easy to use and can be mastered within minutes. In addition, Ant lets you create expanded functionality by extending some of its classes. I will show this expansion in a following example.

What do I need to use Ant?

You must install three components on your machine to run Ant: JDK, XML parser, and Ant (see Resources for links).

In many cases, the XML parser is part of the lib files distributed with the Servlet runner or the Web Server. If not, the free XML parser from java.sun.com is sufficient.

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