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<head>
<meta http-equiv="Content-Language" content="en-us"></meta>
<link rel="stylesheet" type="text/css" href="../stylesheets/style.css">
<title>PreSetDef Task</title>
<style type="text/css">
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</head>
<body>
<h2><a name="presetdef">PreSetDef</a></h2>
<h3>Description</h3>
<p>
The preset definition generates a new definition
based on a current definition with some attributes
or elements preset.
</p>
<p>
<em>since Apache Ant 1.6</em>
</p>
<p>
The resolution of properties in any of the attributes or
nested text takes place with the definition is used and <em>not</em>
when the preset definition is defined.
</p>
<h3>Parameters</h3>
<table border="1" cellpadding="2" cellspacing="0">
<tr>
<td valign="top"><b>Attribute</b></td>
<td valign="top"><b>Description</b></td>
<td align="center" valign="top"><b>Required</b></td>
</tr>
<tr>
<td valign="top">name</td>
<td valign="top">the name of the new definition</td>
<td valign="top" align="center">Yes</td>
</tr>
<tr>
<td valign="top">uri</td>
<td valign="top">
The uri that this definition should live in.
</td>
<td valign="top" align="center">No</td>
</tr>
</table>
<h3>Parameters specified as nested elements</h3>
<h4>another type with attributes or elements set</h4>
<p>The <code><presetdef></code> task takes one nested element as a parameter.
This nested element can be any other type or task. The attributes
and elements that need to be preset are placed here.
</p>
<h3>Examples</h3>
The following fragment defines a javac task with the debug, deprecation
srcdir and destdir
attributes set. It also has a src element to source files from a generated
directory.
<blockquote>
<pre class="code">
<presetdef name="my.javac">
<javac debug="${debug}" deprecation="${deprecation}"
srcdir="${src.dir}" destdir="${classes.dir}">
<src path="${gen.dir}"/>
</javac>
</presetdef>
</pre>
</blockquote>
This can be used as a normal javac task - example:
<blockquote>
<pre class="code">
<my.javac/>
</pre>
</blockquote>
The attributes specified in the preset task may be overridden - i.e.
they may be seen as optional attributes - example:
<blockquote>
<pre class="code">
<my.javac srcdir="${test.src}" deprecation="no"/>
</pre>
</blockquote>
One may put a presetdef definition in an antlib.
For example suppose the jar file antgoodies.jar has
the antlib.xml as follows:
<blockquote>
<pre class="code">
<antlib>
<taskdef resource="com/acme/antgoodies/tasks.properties"/>
<!-- Implement the common use of the javac command -->
<presetdef name="javac">
<javac deprecation="${deprecation}" debug="${debug}"
srcdir="src" destdir="classes"/>
</presetdef>
</antlib>
</pre>
</blockquote>
One may then use this in a build file as follows:
<blockquote>
<pre class="code">
<project default="example" xmlns:antgoodies="antlib:com.acme.antgoodies">
<target name="example">
<!-- Compile source -->
<antgoodies:javac srcdir="src/main"/>
<!-- Compile test code -->
<antgoodies:javac srcdir="src/test"/>
</target>
</project>
</pre>
</blockquote>
<p>
The following is an example of evaluation of properties when the
definition is used:
</p>
<blockquote>
<pre class="code">
<target name="defineandcall">
<presetdef name="showmessage">
<echo>message is '${message}'</echo>
</presetdef>
<showmessage/>
<property name="message" value="Message 1"/>
<showmessage/>
<antcall target="called">
<param name="message" value="Message 2"/>
</antcall>
</target>
<target name="called">
<showmessage/>
</target>
</pre>
</blockquote>
<p>
The command ant defineandcall results in the output:
</p>
<blockquote>
<pre class="code">
defineandcall:
[showmessage] message is '${message}'
[showmessage] message is 'Message 1'
called:
[showmessage] message is 'Message 2'
</pre>
</blockquote>
<p>
It is possible to use a trick to evaluate properties when the definition is
<em>made</em> rather than used. This can be useful if you do not expect some
properties to be available in child builds run with
<code><ant ... inheritall="false"></code>:
</p>
<blockquote><pre class="code">
<macrodef name="showmessage-presetdef">
<attribute name="messageval"/>
<presetdef name="showmessage">
<echo>message is '@{messageval}'</echo>
</presetdef>
</macrodef>
<showmessage-presetdef messageval="${message}"/>
</pre></blockquote>
<hr></hr>
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