| 1 | <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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| 2 | <html>
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| 3 | <head>
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| 4 | <meta http-equiv="Content-Language" content="en-us">
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| 5 | <title>InputHandler</title>
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| 6 | <link rel="stylesheet" type="text/css" href="stylesheets/antmanual.css">
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| 7 | </head>
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| 8 |
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| 9 | <body>
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| 10 | <h1>Using Ant Tasks Outside of Ant</h1>
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| 11 |
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| 12 | <h2>Rationale</h2>
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| 13 |
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| 14 | <p>Ant provides a rich set of tasks for buildfile creators and
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| 15 | administrators. But what about programmers? Can the functionality
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| 16 | provided by Ant tasks be used in java programs?</p>
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| 17 |
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| 18 | <p>Yes, and its quite easy. Before getting into the details, however,
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| 19 | we should mention the pros and cons of this approach:
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| 20 |
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| 21 | <h3>Pros</h3>
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| 22 |
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| 23 | <table border="1" cellpadding="2" cellspacing="0">
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| 24 | <tr>
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| 25 | <td><b>Robust</b></td>
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| 26 | <td>
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| 27 | Ant tasks are very robust. They have been banged on by many people.
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| 28 | Ant tasks have been used in many different contexts, and have
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| 29 | therefore been instrumented to take care of a great many boundary
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| 30 | conditions and potentially obscure errors.
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| 31 | </td>
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| 32 | </tr>
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| 33 | <tr>
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| 34 | <td><b>Cross Platform</b></td>
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| 35 | <td>
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| 36 | Ant tasks are cross platform. They have been tested on all of the
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| 37 | volume platforms, and several rather unusual ones (Netware and OS/390, to
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| 38 | name a few).
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| 39 | </td>
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| 40 | </tr>
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| 41 | <tr>
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| 42 | <td><b>Community Support</b></td>
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| 43 | <td>
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| 44 | Using Ant tasks means you have less of your own code to support. Ant
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| 45 | code is supported by the entire Apache Ant community.
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| 46 | </td>
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| 47 | </tr>
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| 48 | </table>
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| 49 |
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| 50 | <h3>Cons</h3>
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| 51 |
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| 52 | <table border="1" cellpadding="2" cellspacing="0">
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| 53 | <tr>
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| 54 | <td><b>Dependency on Ant Libraries</b></td>
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| 55 | <td>
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| 56 | Obviously, if you use an Ant task in your code, you will have to add
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| 57 | "ant.jar" to your path. Of course, you could use a code optimizer to
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| 58 | remove the unnecessary classes, but you will still probably require a
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| 59 | chunk of the Ant core.
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| 60 | </td>
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| 61 | </tr>
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| 62 | <tr>
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| 63 | <td><b>Loss of Flexibility</b></td>
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| 64 | <td>
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| 65 | At some point, if you find yourself having to modify the Ant code, it
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| 66 | probably makes more sense to "roll your own." Of course, you can
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| 67 | still steal some code snippets and good ideas. This is the beauty of
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| 68 | open source!
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| 69 | </td>
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| 70 | </tr>
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| 71 | </table>
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| 72 |
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| 73 |
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| 74 | <h2>Example</h2>
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| 75 |
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| 76 | <p>Let's say you want to unzip a zip file programmatically from java
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| 77 | into a certain directory. Of course you could write your own routine
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| 78 | to do this, but why not use the Ant task that has already been written?</p>
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| 79 |
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| 80 | <p>In my example, I wanted to be able to unzip a file from within an
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| 81 | XSLT Transformation. XSLT Transformers can be extended by plugging in
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| 82 | static methods in java. I therefore need a function something like
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| 83 | this:</p>
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| 84 |
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| 85 | <pre>
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| 86 | /**
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| 87 | * Unzip a zip file into a given directory.
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| 88 | *
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| 89 | * @param zipFilepath A pathname representing a local zip file
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| 90 | * @param destinationDir where to unzip the archive to
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| 91 | */
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| 92 | static public void unzip(String zipFilepath, String destinationDir)
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| 93 | </pre>
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| 94 |
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| 95 | <p>
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| 96 | The Ant task to perform this function is
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| 97 | <code>org.apache.tools.ant.taskdefs.Expand</code>. All we have to do
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| 98 | is create a dummy Ant <code>Project</code> and <code>Target</code>,
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| 99 | set the <code>Task</code> parameters that would normally be set in a
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| 100 | buildfile, and call <code>execute()</code>.</p>
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| 101 |
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| 102 | <p>First, let's make sure we have the proper includes:</p>
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| 103 |
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| 104 | <pre>
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| 105 | import org.apache.tools.ant.Project;
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| 106 | import org.apache.tools.ant.Target;
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| 107 | import org.apache.tools.ant.taskdefs.Expand;
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| 108 | import java.io.File;
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| 109 | </pre>
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| 110 |
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| 111 | <p>The function call is actually quite simple:</p>
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| 112 |
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| 113 | <pre>
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| 114 | static public void unzip(String zipFilepath, String destinationDir) {
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| 115 |
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| 116 | final class Expander extends Expand {
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| 117 | public Expander() {
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| 118 | project = new Project();
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| 119 | project.init();
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| 120 | taskType = "unzip";
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| 121 | taskName = "unzip";
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| 122 | target = new Target();
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| 123 | }
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| 124 | }
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| 125 | Expander expander = new Expander();
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| 126 | expander.setSrc(new File(zipfile));
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| 127 | expander.setDest(new File(destdir));
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| 128 | expander.execute();
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| 129 | </pre>
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| 130 |
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| 131 | <p>In actual practice, you will probably want to add your own error
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| 132 | handling code and you may not want to use a local inner class.
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| 133 | However, the point of the example is to show how an Ant task can be
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| 134 | called programmatically in relatively few lines of code.</p>
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| 135 |
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| 136 | <p>The question you are probably asking yourself at this point is:
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| 137 | <i>How would I know which classes and methods have to be called in
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| 138 | order to set up a dummy Project and Target?</i> The answer is: you
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| 139 | don't. Ultimately, you have to be willing to get your feet wet and
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| 140 | read the source code. The above example is merely designed to whet
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| 141 | your appetite and get you started. Go for it!</p>
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| 142 |
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| 143 | <hr>
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| 144 | <p align="center">Copyright © 2002-2004 The Apache Software Foundation. All rights
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| 145 | Reserved.</p>
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| 146 | </html>
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