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158 lines
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158 lines
5.0 KiB
HTML
<!DOCTYPE html>
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<!--
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Licensed to the Apache Software Foundation (ASF) under one or more
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contributor license agreements. See the NOTICE file distributed with
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this work for additional information regarding copyright ownership.
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The ASF licenses this file to You under the Apache License, Version 2.0
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(the "License"); you may not use this file except in compliance with
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the License. You may obtain a copy of the License at
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https://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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-->
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<html lang="en">
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<head>
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<link rel="stylesheet" type="text/css" href="stylesheets/style.css">
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<title>InputHandler</title>
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</head>
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<body>
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<h1>Using Apache Ant™ Tasks Outside of Ant</h1>
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<h2>Rationale</h2>
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<p>Apache Ant provides a rich set of tasks for buildfile creators and
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administrators. But what about programmers? Can the functionality
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provided by Ant tasks be used in Java programs?</p>
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<p>Yes, and its quite easy. Before getting into the details, however,
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we should mention the pros and cons of this approach:
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<h3>Pros</h3>
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<table>
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<tr>
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<td><strong>Robust</strong></td>
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<td>
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Ant tasks are very robust. They have been banged on by many people.
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Ant tasks have been used in many different contexts, and have
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therefore been instrumented to take care of a great many boundary
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conditions and potentially obscure errors.
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</td>
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</tr>
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<tr>
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<td><strong>Cross Platform</strong></td>
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<td>
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Ant tasks are cross platform. They have been tested on all of the
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volume platforms, and several rather unusual ones (Netware and OS/390, to
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name a few).
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</td>
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</tr>
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<tr>
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<td><strong>Community Support</strong></td>
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<td>
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Using Ant tasks means you have less of your own code to support. Ant
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code is supported by the entire Apache Ant community.
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</td>
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</tr>
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</table>
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<h3>Cons</h3>
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<table>
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<tr>
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<td><strong>Dependency on Ant Libraries</strong></td>
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<td>
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Obviously, if you use an Ant task in your code, you will have to add
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<q>ant.jar</q> to your path. Of course, you could use a code optimizer to
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remove the unnecessary classes, but you will still probably require a
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chunk of the Ant core.
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</td>
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</tr>
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<tr>
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<td><strong>Loss of Flexibility</strong></td>
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<td>
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At some point, if you find yourself having to modify the Ant code, it
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probably makes more sense to "roll your own." Of course, you can
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still steal some code snippets and good ideas. This is the beauty of
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open source!
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</td>
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</tr>
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</table>
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<h2>Example</h2>
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<p>Let's say you want to unzip a zip file programmatically from java
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into a certain directory. Of course you could write your own routine
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to do this, but why not use the Ant task that has already been written?</p>
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<p>In my example, I wanted to be able to unzip a file from within an
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XSLT Transformation. XSLT Transformers can be extended by plugging in
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static methods in java. I therefore need a function something like
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this:</p>
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<pre>
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/**
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* Unzip a zip file into a given directory.
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*
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* @param zipFilepath A pathname representing a local zip file
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* @param destinationDir where to unzip the archive to
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*/
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static public void unzip(String zipFilepath, String destinationDir)
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</pre>
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<p>
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The Ant task to perform this function
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is <code>org.apache.tools.ant.taskdefs.Expand</code>. All we have to do
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is create a dummy Ant <code>Project</code> and <code>Target</code>,
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set the <code>Task</code> parameters that would normally be set in a
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buildfile, and call <code>execute()</code>.</p>
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<p>First, let's make sure we have the proper includes:</p>
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<pre>
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import org.apache.tools.ant.Project;
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import org.apache.tools.ant.Target;
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import org.apache.tools.ant.taskdefs.Expand;
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import java.io.File;</pre>
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<p>The function call is actually quite simple:</p>
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<pre>
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static public void unzip(String zipFilepath, String destinationDir) {
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final class Expander extends Expand {
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public Expander() {
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project = new Project();
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project.init();
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taskType = "unzip";
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taskName = "unzip";
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target = new Target();
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}
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}
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Expander expander = new Expander();
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expander.setSrc(new File(zipfile));
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expander.setDest(new File(destdir));
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expander.execute();
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}</pre>
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<p>In actual practice, you will probably want to add your own error
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handling code and you may not want to use a local inner class.
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However, the point of the example is to show how an Ant task can be
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called programmatically in relatively few lines of code.</p>
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<p>The question you are probably asking yourself at this point
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is: <em>How would I know which classes and methods have to be called in
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order to set up a dummy Project and Target?</em> The answer is: you
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don't. Ultimately, you have to be willing to get your feet wet and
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read the source code. The above example is merely designed to whet
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your appetite and get you started. Go for it!</p>
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</body>
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</html>
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