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    <h2><a name="antlib">Antlib</a></h2>


    <h3>Description</h3>
    <p>
      An antlib file is an xml file with a root element of "antlib".
      Antlib's elements are Apache Ant definition tasks - like
      
      and <a href="../Tasks/taskdef.html">Taskdef</a>,
      or any Ant task that extends
      <code>org.apache.tools.ant.taskdefs.AntlibDefinition</code>.
    </p>
    <p>
        The current set of declarations bundled with Ant that do this are:
    </p>
        <ol>
            <li><a href="../Tasks/typedef.html">Typedef</a>
            </li>
            <li><a href="../Tasks/taskdef.html">Taskdef</a>
            </li>
            <li><a href="../Tasks/macrodef.html">Macrodef</a>
            </li>
            <li><a href="../Tasks/presetdef.html">Presetdef</a>
            </li>
            <li><a href="../Tasks/scriptdef.html">Scriptdef</a>
            </li>
        </ol>
    <p>
      A group of tasks and types may be defined together in an antlib
      file. For example the file <i>sample.xml</i> contains the following:
    </p>
    <blockquote>
      <pre>
&lt;?xml version="1.0"?&gt;
&lt;antlib&gt;
   &lt;typedef name="if" classname="org.acme.ant.If"/&gt;
   &lt;typedef name="scriptpathmapper"
            classname="org.acme.ant.ScriptPathMapper"
            onerror="ignore"/&gt;
   &lt;macrodef name="print"&gt;
      &lt;attribute name="file"/&gt;
      &lt;sequential&gt;
         &lt;concat taskname="print"&gt;
            &lt;fileset dir="." includes="@{file}"/&gt;
         &lt;/concat&gt;
      &lt;/sequential&gt;
   &lt;/macrodef&gt;
&lt;/antlib&gt;
      </pre>
    </blockquote>
    <p>
      It defines two types or tasks, <i>if</i> and <i>scriptpathmapper</i>.
      This antlib file may be used in a build script as follows:
    </p>
    <blockquote>
      <pre>
&lt;typedef file="sample.xml"/&gt;
      </pre>
    </blockquote>
    <p>
      The other attributes of <code>&lt;typedef&gt;</code> may be used as well.
      For example, assuming that the <i>sample.xml</i> is in a jar
      file <i>sample.jar</i> also containing the classes, the
      following build fragment will define the <i>if</i> and <i>scriptpathmapper</i>
      tasks/types and place them in the namespace uri <i>samples:/acme.org</i>.
    </p>
    <blockquote>
      <pre>
&lt;typedef resource="org/acme/ant/sample.xml"
         uri="samples:/acme.org"/&gt;
      </pre>
    </blockquote>
    <p>
      The definitions may then be used as follows:
    </p>
    <blockquote>
      <pre>
&lt;sample:if valuetrue="${props}" xmlns:sample="samples:/acme.org"&gt;
   &lt;sample:scriptpathmapper language="beanshell"&gt;
      some bean shell
   &lt;/sample:scriptpathmapper&gt;
&lt;/sample:if&gt;
      </pre>
    </blockquote>


    <h3><a name="antlibnamespace">Antlib namespace</a></h3>
    <p>
      The name space URIs with the pattern <b>antlib:<i>java package</i></b>
      are given special treatment.
    </p>
    <p>
      When Ant encounters a element with a namespace URI with this pattern, it
      will check to see if there is a resource of the name <i>antlib.xml</i> in
      the package directory in the default classpath.
    </p>
    <p>
      For example, assuming that the file <i>antcontrib.jar</i> has been placed
      in the directory <i>${ant.home}/lib</i> and it contains the resource
      <i>net/sf/antcontrib/antlib.xml</i> which has all antcontrib's definitions
      defined, the following build file will automatically load the antcontrib
      definitions at location <i>HERE</i>:
    </p>
    <blockquote>
      <pre>
&lt;project default="deletetest" xmlns:antcontrib="antlib:net.sf.antcontrib"&gt;
   &lt;macrodef name="showdir"&gt;
      &lt;attribute name="dir"/&gt;
      &lt;sequential&gt;
         &lt;antcontrib:shellscript shell="bash"&gt;  &lt;!-- HERE --&gt;
            ls -Rl @{dir}
         &lt;/antcontrib:shellscript&gt;
      &lt;/sequential&gt;
   &lt;/macrodef&gt;

   &lt;target name="deletetest"&gt;
      &lt;delete dir="a" quiet="yes"/&gt;
      &lt;mkdir dir="a/b"/&gt;
      &lt;touch file="a/a.txt"/&gt;
      &lt;touch file="a/b/b.txt"/&gt;
      &lt;delete&gt;
         &lt;fileset dir="a"/&gt;
      &lt;/delete&gt;
      &lt;showdir dir="a"/&gt;
   &lt;/target&gt;
&lt;/project&gt;
      </pre>
    </blockquote>
    <p>
      The requirement that the resource is in the default classpath
      may be removed in future versions of Ant.</p>
    </p>


	<h3><a name="loadFromInside">Load antlib from inside of the buildfile</a></h3>
	<p>
	  If you want to separate the antlib from your local Ant installation, e.g. because you 
	  want to hold that jar in your projects SCM system, you have to specify a classpath, so 
	  that Ant could find that jar. The best solution is loading the antlib with <tt>&lt;taskdef&gt;</tt>.
	</p>
    <blockquote>
      <pre>
&lt;project xmlns:<font color="green">antcontrib</font>="<font color="red">antlib:net.sf.antcontrib</font>"&gt;
   &lt;taskdef uri="<font color="red">antlib:net.sf.antcontrib</font>"
            resource="net/sf/antcontrib/antlib.xml"
            classpath="path/to/ant-contrib.jar"/&gt;
   
   &lt;target name="iterate"&gt;
      &lt;<font color="green">antcontrib</font>:for param="file"&gt;
         &lt;fileset dir="."/&gt;
         &lt;sequential&gt;
            &lt;echo message="- @{file}"/&gt;
         &lt;/sequential&gt;
      &lt;/antcontrib:for&gt;
   &lt;/target&gt;
&lt;/project&gt;
      </pre>
    </blockquote>

	
    <h3><a name="currentnamespace">Current namespace</a></h3>
    <p>
      Definitions defined in antlibs may be used in antlibs. However
      the namespace that definitions are placed in are dependent on
      the <code>&lt;typedef&gt;</code> that uses the antlib. To deal with this
      problem, the definitions are placed in the namespace URI <i>ant:current</i>
      for the duration of the antlib execution.
      For example the following antlib defines the task <code>&lt;if&gt;</code>, the
      type <code>&lt;isallowed&gt;</code> and a macro
      <code>&lt;ifallowed&gt;</code> that makes use of the task and type:
    </p>
    <blockquote>
      <pre>
&lt;antlib xmlns:current="ant:current"&gt;
   &lt;taskdef name="if" classname="org.acme.ant.If"/&gt;
   &lt;typedef name="isallowed" classname="org.acme.ant.Isallowed"/&gt;
   &lt;macrodef name="ifallowed"&gt;
      &lt;attribute name="action"/&gt;
      &lt;element name="do"/&gt;
      &lt;sequential&gt;
         &lt;current:if&gt;
            &lt;current:isallowed test="@{action}"/&gt;
            &lt;current:then&gt;
               &lt;do/&gt;
            &lt;/current:then&gt;
         &lt;/current:if&gt;
      &lt;/sequential&gt;
   &lt;/macrodef&gt;
&lt;/antlib&gt;
      </pre>
    </blockquote>


    <h3>Other examples and comments</h3>
    <p>
      Antlibs may make use of other antlibs.
    </p>
    <p>
      As the names defined in the antlib are in the namespace uri as
      specified by the calling <code>&lt;typedef&gt;</code> or by automatic element
      resolution, one may reuse names from core ant types and tasks,
      provided the caller uses a namespace uri. For example, the
      following antlib may be used to define defaults for various
      tasks:
    </p>
    <blockquote>
      <pre>
&lt;antlib xmlns:antcontrib="antlib:net.sf.antcontrib"&gt;
   &lt;presetdef name="javac"&gt;
      &lt;javac deprecation="${deprecation}"
             debug="${debug}"/&gt;
   &lt;/presetdef&gt;
   &lt;presetdef name="delete"&gt;
      &lt;delete quiet="yes"/&gt;
   &lt;/presetdef&gt;
   &lt;presetdef name="shellscript"&gt;
      &lt;antcontrib:shellscript shell="bash"/&gt;
   &lt;/presetdef&gt;
&lt;/antlib&gt;
      </pre>
    </blockquote>
    <p>
      This may be used as follows:
    </p>
    <blockquote>
      <pre>
&lt;project xmlns:local="localpresets"&gt;
   &lt;typedef file="localpresets.xml" uri="localpresets"/&gt;
   &lt;local:shellscript&gt;
      echo "hello world"
   &lt;/local:shellscript&gt;
&lt;/project&gt;
      </pre>
    </blockquote>
    

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