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    <title>PreSetDef Task</title>
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    <h2 id="presetdef">PreSetDef</h2>
    <p><em>Since Apache Ant 1.6</em></p>
    <h3>Description</h3>
    <p>The preset definition generates a new definition based on a current definition with some
      attributes or elements preset.</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 class="attr">
      <tr>
        <th scope="col">Attribute</th>
        <th scope="col">Description</th>
        <th scope="col">Required</th>
      </tr>
      <tr>
        <td>name</td>
        <td>the name of the new definition</td>
        <td>Yes</td>
      </tr>
      <tr>
        <td>uri</td>
        <td>The URI that this definition should live in.</td>
        <td>No</td>
      </tr>
    </table>
    <h3>Parameters specified as nested elements</h3>
    <h4>another type with attributes or elements set</h4>
    <p>The <code>&lt;presetdef&gt;</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>
    <p>The following fragment defines a <code>javac</code> task with
      the <var>debug</var>, <var>deprecation</var>, <var>srcdir</var> and <var>destdir</var>
      attributes set. It also has a <code>src</code> element to source files from a generated
      directory.</p>
    <pre>
&lt;presetdef name="my.javac"&gt;
   &lt;javac debug="${debug}" deprecation="${deprecation}"
          srcdir="${src.dir}" destdir="${classes.dir}"&gt;
      &lt;src path="${gen.dir}"/&gt;
   &lt;/javac&gt;
&lt;/presetdef&gt;</pre>
    <p>This can be used as a normal <code>javac</code> task&mdash;for example:</p>
    <pre>&lt;my.javac/&gt;</pre>
    <p>The attributes specified in the preset task may be overridden&mdash;i.e.  they may be seen as
      optional attributes&mdash;for example:</p>
    <pre>&lt;my.javac srcdir="${test.src}" deprecation="no"/&gt;</pre>
    <p>One may put a <code>presetdef</code> definition in an antlib.  For example suppose the jar
      file <samp>antgoodies.jar</samp> has the <samp>antlib.xml</samp> as follows:</p>
    <pre>
&lt;antlib&gt;
   &lt;taskdef resource="com/acme/antgoodies/tasks.properties"/&gt;
   &lt;!-- Implement the common use of the javac command --&gt;
   &lt;presetdef name="javac"&gt;
      &lt;javac deprecation="${deprecation}" debug="${debug}"
             srcdir="src" destdir="classes"/&gt;
   &lt;/presetdef&gt;
&lt;/antlib&gt;</pre>
    <p>One may then use this in a build file as follows:</p>
    <pre>
&lt;project default="example" xmlns:antgoodies="antlib:com.acme.antgoodies"&gt;
   &lt;target name="example"&gt;
      &lt;!-- Compile source --&gt;
      &lt;antgoodies:javac srcdir="src/main"/&gt;
      &lt;!-- Compile test code --&gt;
      &lt;antgoodies:javac srcdir="src/test"/&gt;
   &lt;/target&gt;
&lt;/project&gt;</pre>
    <p>The following is an example of evaluation of properties when the definition is used:</p>
    <pre>
&lt;target name="defineandcall"&gt;
   &lt;presetdef name="showmessage"&gt;
      &lt;echo&gt;message is '${message}'&lt;/echo&gt;
   &lt;/presetdef&gt;
   &lt;showmessage/&gt;
   &lt;property name="message" value="Message 1"/&gt;
   &lt;showmessage/&gt;
   &lt;antcall target="called"&gt;
      &lt;param name="message" value="Message 2"/&gt;
   &lt;/antcall&gt;
&lt;/target&gt;
&lt;target name="called"&gt;
   &lt;showmessage/&gt;
&lt;/target&gt;</pre>
    <p>The command <kbd>ant defineandcall</kbd> results in the output:</p>
    <pre class="output">
defineandcall:
[showmessage] message is '${message}'
[showmessage] message is 'Message 1'

called:
[showmessage] message is 'Message 2'</pre>
    <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>&lt;ant ... inheritall="false"&gt;</code>:</p>
    <pre>
&lt;macrodef name="showmessage-presetdef"&gt;
  &lt;attribute name="messageval"/&gt;
  &lt;presetdef name="showmessage"&gt;
    &lt;echo&gt;message is '@{messageval}'&lt;/echo&gt;
  &lt;/presetdef&gt;
&lt;/macrodef&gt;
&lt;showmessage-presetdef messageval="${message}"/&gt;</pre>

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