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<h2 id="typedef">Typedef</h2>
<h3>Description</h3>
<p>Adds a task or a data type definition to the current project such that this new type or task can
be used in the current project.</p>
<p>A Task is any class that extends <code>org.apache.tools.ant.Task</code> or can be adapted as a
Task using an adapter class.</p>
<p>Data types are things like <a href="../using.html#path">paths</a>
or <a href="../Types/fileset.html">filesets</a> that can be defined at the project level and
referenced via their <var>id</var> attribute.  Custom data types usually need custom tasks to put
them to good use.</p>
<p>Two attributes are needed to make a definition: the name that identifies this data type uniquely,
and the full name of the class (including its package name) that implements this type.</p>
<p>You can also define a group of definitions at once using the file or resource attributes.  These
attributes point to files in the format of Java property files or an xml format.</p>
<p>For property files each line defines a single data type in the format:</p>
<pre>typename=fully.qualified.java.classname</pre>
<p>The xml format is described in the <a href="../Types/antlib.html">Antlib</a> section.</p>

<p>If you are defining tasks or types that share the same classpath with
multiple <code>taskdef</code> or <code>typedef</code> tasks, the corresponding classes will be
loaded by different
Java <a href="http://docs.oracle.com/javase/8/docs/api/java/lang/ClassLoader.html">ClassLoaders</a>.
Two classes with the same name loaded via different ClassLoaders are not the same class from the
point of view of JVM, they don't share static variables and instances of these classes can't access
private methods or attributes of instances defined by "the other class" of the same name.  They
don't even belong to the same Java package and can't access package private code, either.</p>

<p>The best way to load several tasks/types that are supposed to cooperate with each other via
shared Java code is to use the <var>resource</var> attribute and an <code>antlib</code> descriptor.
If this is not possible, the second best option is to use the <var>loaderref</var> attribute and
specify the same name for each and every <code>typedef</code>/<code>taskdef</code> -- this way the
classes will share the same <code>ClassLoader</code>.  Note that
the <code>typedef</code>/<code>taskdef</code> tasks must use identical classpath definitions (this
includes the order of path components) for the <var>loaderref</var> attribute to work.</p>

<h3>Parameters</h3>
<table class="attr">
  <tr>
    <th>Attribute</th>
    <th>Description</th>
    <th>Required</th>
  </tr>
  <tr>
    <td>name</td>
    <td>the name of the data type</td>
    <td rowspan="2">Yes, unless <var>file</var> or <var>resource</var> attributes have been
      specified.</td>
  </tr>
  <tr>
    <td>classname</td>
    <td class="left">the full class name implementing the data type</td>
  </tr>
  <tr>
    <td>file</td>
    <td>Name of the file to load definitions from.</td>
    <td>No</td>
  </tr>
  <tr>
    <td>resource</td>
    <td>Name of the resource to load definitions from.  If multiple resources by this name are found
      along the classpath, and <var>format</var> is <q>properties</q>, the first resource will be
      loaded; otherwise all such resources will be loaded.</td>
    <td>No</td>
  </tr>
  <tr>
    <td>format</td>
    <td>The format of the file or resource. The values are <q>properties</q>" or <q>xml</q>. If the
      value is <q>properties</q> the file/resource is a property file contains name-classname
      pairs. If the value is <q>xml</q>, the file/resource is an XML file/resource structured
      according to <a href="../Types/antlib.html">Antlib</a>.  The default is <q>properties</q>
      unless the file/resource name ends with <samp>.xml</samp>, in which case the <var>format</var>
      attribute will have the value <q>xml</q>.  <em>Since Ant 1.6</em></td>
    <td>No</td>
  </tr>
  <tr>
    <td>classpath</td>
    <td>the classpath to use when looking up <var>classname</var>.</td>
    <td>No</td>
  </tr>
  <tr>
    <td>classpathref</td>
    <td>a reference to a classpath to use when looking up <var>classname</var>.</td>
    <td>No</td>
  </tr>
  <tr>
    <td>loaderRef</td>
    <td>the name of the loader that is used to load the class, constructed from the specified
      classpath. Use this to allow multiple tasks/types to be loaded with the same loader, so they
      can call each other. <em>Since Ant 1.5</em></td>
    <td>No</td>
  </tr>
  <tr>
    <td>onerror</td>
    <td>The action to take if there was a failure in defining the type. The values are <q>fail</q>:
      cause a build exception; <q>report</q>: output a warning, but continue; <q>ignore</q>: do
      nothing.  <em>Since Ant 1.6</em>, an additional value is <q>failall</q>: cause all behavior of
      fail, as well as a build exception for the resource or file attribute if the resource or file
      is not found.</td>
    <td>No; default is <q>fail</q> (<em>since Ant 1.7</em>)</td>
  </tr>
  <tr>
    <td>adapter</td>
    <td>A class that is used to adapt the defined class to another interface/class. The adapter
      class must implement the interface <code>org.apache.tools.ant.TypeAdapter</code>. The adapter
      class will be used to wrap the defined class unless the defined class implements/extends the
      class defined by the attribute <q>adaptto</q>.  If <q>adaptto</q> is not set, the defined
      class will always be wrapped.  <em>Since Ant 1.6</em></td>
    <td>No</td>
  </tr>
  <tr>
    <td>adaptto</td>
    <td>This attribute is used in conjunction with the adapter attribute.  If the defined class does
      not implement/extend the interface/class specified by this attribute, the adaptor class will
      be used to wrap the class. <em>Since Ant 1.6</em></td>
    <td>No</td>
  </tr>
  <tr>
    <td>uri</td>
    <td>The uri that this definition should live in.  <em>Since Ant 1.6</em></td>
    <td>No</td>
  </tr>
</table>
<h3>Parameters specified as nested elements</h3>
<h4>classpath</h4>
<p><code>Typedef</code>'s <var>classpath</var> attribute is a <a href="../using.html#path">path-like
structure</a> and can also be set via a nested <code>classpath</code> element.</p>

<h3>Examples</h3>
<p>The following fragment defines define a type called <code>urlset</code>.</p>
<pre>&lt;typedef name="urlset" classname="com.mydomain.URLSet"/&gt;</pre>
<p>The data type is now available to Ant. The class <code>com.mydomain.URLSet</code> implements this
type.</p>

<p>Assuming a class <code>org.acme.ant.RunnableAdapter</code> that extends Task and
implements <code>org.apache.tools.ant.TypeAdapter</code>, and in the execute method
invokes <code>run()</code> on the proxied object, one may use a Runnable class as an Ant task. The
following fragment defines a task called <code>runclock</code>.</p>
<pre>
&lt;typedef name="runclock"
         classname="com.acme.ant.RunClock"
         adapter="org.acme.ant.RunnableAdapter"/&gt;</pre>

<p>The following fragment shows the use of the <var>classpathref</var> and <var>loaderref</var> to
load up two definitions.</p>
<pre>
&lt;path id="lib.path"&gt;
    &lt;fileset dir="lib" includes="lib/*.jar"/&gt;
&lt;/path&gt;

&lt;typedef name="filter1"
         classname="org.acme.filters.Filter1"
         classpathref="lib.path"
         loaderref="lib.path.loader"/&gt;
&lt;typedef name="filter2"
         classname="org.acme.filters.Filter2"
         loaderref="lib.path.loader"/&gt;</pre>

<p>If you want to load an antlib into a special xml-namespace, the <tt>uri</tt> attribute is
important:</p>
<pre>
&lt;project xmlns:antcontrib="antlib:net.sf.antcontrib"&gt;
     &lt;taskdef uri="antlib:net.sf.antcontrib"
              resource="net/sf/antcontrib/antlib.xml"
              classpath="path/to/ant-contrib.jar"/&gt;</pre>

<p>Here the namespace declaration <code>xmlns:antcontrib="antlib:net.sf.antcontrib"</code> allows
tasks and types of the AntContrib Antlib to be used with the <samp>antcontrib</samp> prefix
like <code>&lt;antcontrib:if&gt;</code>.  The normal rules of XML namespaces apply and you can
declare the prefix at any element to make it usable for the element it is declared on as well as all
its child elements.</p>

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