wangwei
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antliscence
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<h2><a name="available">Available</a></h2>
<h3>Description</h3>
<p>Sets a property if a resource is available at runtime. This resource can be a
file, a directory, a class in the classpath, or a JVM system resource.</p>
<p>If the resource is present, the property value is set to true by
default; otherwise, the property is not set. You can set the value to
something other than the default by specifying the <code>value</code> attribute.</p>
<p>Normally, this task is used to set properties that are useful to avoid target
execution depending on system parameters.</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">property</td>
    <td valign="top">The name of the property to set.</td>
    <td valign="top" align="center">Yes</td>
  </tr>
  <tr>
    <td valign="top">value</td>
    <td valign="top">The value to set the property to. Defaults to &quot;true&quot;.</td>
    <td valign="top" align="center">No</td>
  </tr>
  <tr>
    <td valign="top">classname</td>
    <td valign="top">The class to look for in the classpath.</td>
    <td valign="middle" align="center" rowspan="3">Yes</td>
  </tr>
  <tr>
    <td valign="top">file</td>
    <td valign="top">The file to look for.</td>
  </tr>
  <tr>
    <td valign="top">resource</td>
    <td valign="top">The resource to look for in the JVM.</td>
  </tr>
  <tr>
    <td valign="top">classpath</td>
    <td valign="top">The classpath to use when looking up <code>classname</code> or <code>resource</code>.</td>
    <td align="center" valign="top">No</td>
  </tr>
  <tr>
    <td valign="top">filepath</td>
    <td valign="top">The path to use when looking up <code>file</code>.</td>
    <td align="center" valign="top">No</td>
  </tr>
  <tr>
    <td valign="top">classpathref</td>
    <td valign="top">The classpath to use, given as a <a href="../using.html#references">reference</a> to a path defined elsewhere.</td>
    <td align="center" valign="top">No</td>
  </tr>
  <tr>
    <td valign="top">type</td>
    <td valign="top">The type of <code>file</code> to look for, either a directory (<code>type=&quot;dir&quot;</code>) or a file
      (<code>type=&quot;file&quot;</code>). If not set, the property will be set if the name specified in the <code>file</code>
      attribute exists as either a file or a directory.</td>
    <td align="center" valign="top">No</td>
  </tr>
  <tr>
    <td valign="top">ignoresystemclasses</td>
    <td valign="top">Ignore Ant's runtime classes, using only the specified
      classpath.  Only affects the "classname" attribute.  Defaults to &quot;false&quot;</td>
    <td align="center" valign="top">No</td>
  </tr>
  <tr>
    <td valign="top">searchparents</td>
    <td valign="top">This contains the behaviour of the "file" type.
      If true, the available task will, when
      searching for a file, search not only the directories specified but
      will also search the parent and grandparent directories of those
      specified.
      If false, only the directories specified will be searched.
      Defaults to "true".
      <em>Since Ant 1.7</em>
    </td>
    <td align="center" valign="top">No</td>
  </tr>
</table>
<h3>Parameters specified as nested elements</h3>
<h4>classpath</h4>
<p><code>Available</code>'s <code>classpath</code> attribute is a <a
href="../using.html#path">path-like structure</a> and can also be set via a nested
<code>&lt;classpath&gt;</code> element.</p>
<h4>filepath</h4>
<p><code>Available</code>'s <code>filepath</code> attribute is a <a
href="../using.html#path">path-like structure</a> and can also be set via a nested
<code>&lt;filepath&gt;</code> element.</p>
<h3>Examples</h3>
<blockquote><pre>
&lt;available classname=&quot;org.whatever.Myclass&quot; property=&quot;Myclass.present&quot;/&gt;
</pre></blockquote>
<p>sets the <code>Myclass.present</code> property to the value &quot;true&quot;
if the class <code>org.whatever.Myclass</code> is found in Ant's classpath.</p>
<blockquote><pre>
&lt;property name=&quot;jaxp.jar&quot; value=&quot;./lib/jaxp11/jaxp.jar&quot;/&gt;
&lt;available file=&quot;${jaxp.jar}&quot; property=&quot;jaxp.jar.present&quot;/&gt;
</pre></blockquote>
<p>sets the <code>jaxp.jar.present</code> property to the value &quot;true&quot;
if the file <code>./lib/jaxp11/jaxp.jar</code> is found.</p>
<blockquote><pre>
&lt;available file=&quot;/usr/local/lib&quot; type=&quot;dir&quot;
           property=&quot;local.lib.present&quot;/&gt;
</pre></blockquote>
<p>sets the <code>local.lib.present</code> property to the value &quot;true&quot;
if the directory <code>/usr/local/lib</code> is found.</p>
<blockquote><pre>
...in project ...
&lt;property name=&quot;jaxp.jar&quot; value=&quot;./lib/jaxp11/jaxp.jar&quot;/&gt;
&lt;path id=&quot;jaxp&quot; location=&quot;${jaxp.jar}&quot;/&gt;
...in target ...
&lt;available classname=&quot;javax.xml.transform.Transformer&quot;
           classpathref=&quot;jaxp&quot; property=&quot;jaxp11.present&quot;/&gt;
</pre></blockquote>
<p>sets the <code>jaxp11.present</code> property to the value &quot;true&quot;
if the class <code>javax.xml.transform.Transformer</code> is found in the classpath referenced by <code>jaxp</code> (in this case, <code>./lib/jaxp11/jaxp.jar</code>).
</p>
<blockquote><pre>
&lt;available property=&quot;have.extras&quot; resource=&quot;extratasks.properties&quot;&gt;
  &lt;classpath&gt;
    &lt;pathelement location=&quot;/usr/local/ant/extra.jar&quot; /&gt;
&nbsp;&nbsp;&lt;/classpath&gt;
&lt;/available&gt;
</pre></blockquote>
<p>sets the <code>have.extras</code> property to the value &quot;true&quot;
if the resource-file <code>extratasks.properties</code> is found.
</p>
<hr><p align="center">Copyright &copy; 2000-2002,2004-2006 The Apache Software Foundation. All rights
Reserved.</p>

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