Developing with Apache AntUsing Ant Tasks Outside of AntUsing Apache Ant™ Tasks Outside of AntRationaleApache Ant provides a rich set of tasks for buildfile creators andadministrators. But what about programmers? Can the functionalityprovided by Ant tasks be used in java programs? Yes, and its quite easy. Before getting into the details, however, we should mention the pros and cons of this approach: Pros| Robust | Ant tasks are very robust. They have been banged on by many people.Ant tasks have been used in many different contexts, and havetherefore been instrumented to take care of a great many boundaryconditions and potentially obscure errors. | | Cross Platform | Ant tasks are cross platform. They have been tested on all of thevolume platforms, and several rather unusual ones (Netware and OS/390, toname a few). | | Community Support | Using Ant tasks means you have less of your own code to support. Antcode is supported by the entire Apache Ant community. |
Cons| Dependency on Ant Libraries | Obviously, if you use an Ant task in your code, you will have to add"ant.jar" to your path. Of course, you could use a code optimizer toremove the unnecessary classes, but you will still probably require achunk of the Ant core. | | Loss of Flexibility | At some point, if you find yourself having to modify the Ant code, itprobably makes more sense to "roll your own." Of course, you canstill steal some code snippets and good ideas. This is the beauty ofopen source! |
ExampleLet's say you want to unzip a zip file programmatically from javainto a certain directory. Of course you could write your own routineto do this, but why not use the Ant task that has already been written? In my example, I wanted to be able to unzip a file from within anXSLT Transformation. XSLT Transformers can be extended by plugging instatic methods in java. I therefore need a function something likethis: /** * Unzip a zip file into a given directory. * * @param zipFilepath A pathname representing a local zip file * @param destinationDir where to unzip the archive to */ static public void unzip(String zipFilepath, String destinationDir) The Ant task to perform this function isorg.apache.tools.ant.taskdefs.Expand. All we have to dois create a dummy Ant Project and Target,set the Task parameters that would normally be set in abuildfile, and call execute(). First, let's make sure we have the proper includes: import org.apache.tools.ant.Project;import org.apache.tools.ant.Target;import org.apache.tools.ant.taskdefs.Expand;import java.io.File; The function call is actually quite simple: static public void unzip(String zipFilepath, String destinationDir) { final class Expander extends Expand { public Expander() { project = new Project(); project.init(); taskType = "unzip"; taskName = "unzip"; target = new Target();} } Expander expander = new Expander(); expander.setSrc(new File(zipfile)); expander.setDest(new File(destdir)); expander.execute();In actual practice, you will probably want to add your own errorhandling code and you may not want to use a local inner class.However, the point of the example is to show how an Ant task can becalled programmatically in relatively few lines of code. The question you are probably asking yourself at this point is:How would I know which classes and methods have to be called inorder to set up a dummy Project and Target? The answer is: youdon't. Ultimately, you have to be willing to get your feet wet andread the source code. The above example is merely designed to whetyour appetite and get you started. Go for it! | 
