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<h2><a name="jar">Jar</a></h2>
<h3>Description</h3>
<p>Jars a set of files.</p>
<p>The <i>basedir</i> attribute is the reference directory from where to jar.</p>
<p>Note that file permissions will not be stored in the resulting jarfile.</p>
<p>It is possible to refine the set of files that are being jarred. This can be
done with the <i>includes</i>, <i>includesfile</i>, <i>excludes</i>, <i>excludesfile</i> and <i>defaultexcludes</i>
attributes. With the <i>includes</i> or <i>includesfile</i> attribute you specify the files you want to
have included by using patterns. The <i>exclude</i> or <i>excludesfile</i> attribute is used to specify
the files you want to have excluded. This is also done with patterns. And
finally with the <i>defaultexcludes</i> attribute, you can specify whether you
want to use default exclusions or not. See the section on <a
href="../dirtasks.html#directorybasedtasks">directory based tasks</a>, on how the
inclusion/exclusion of files works, and how to write patterns.</p>
<p>This task forms an implicit <a href="../Types/fileset.html">FileSet</a> and
supports most attributes of <code>&lt;fileset&gt;</code>
(<code>dir</code> becomes <code>basedir</code>) as well as the nested
<code>&lt;include&gt;</code>, <code>&lt;exclude&gt;</code> and
<code>&lt;patternset&gt;</code> elements.</p>
<p>You can also use nested file sets for more flexibility, and specify
multiple ones to merge together different trees of files into one JAR.
The extended fileset and groupfileset child elements from the zip task are
also available in the jar task.
See the <a href="zip.html">Zip</a> task for more details and examples.</p>

<p>The <code>update</code> parameter controls what happens if the JAR
file already exists. When set to <code>yes</code>, the JAR file is
updated with the files specified. When set to <code>no</code> (the
default) the JAR file is overwritten. An example use of this is
provided in the <a href="zip.html">Zip task documentation</a>.  Please
note that ZIP files store file modification times with a granularity
of two seconds.  If a file is less than two seconds newer than the
entry in the archive, Ant will not consider it newer.</p>

<p>If the manifest is omitted, a simple one will be supplied by Apache Ant.</p>

<p>The <code>whenmanifestonly</code> parameter controls what happens when no
files, apart from the manifest file, or nested services, match.
If <code>skip</code>, the JAR is not created and a warning is issued.
If <code>fail</code>, the JAR is not created and the build is halted with an error.
If <code>create</code>, (default) an empty JAR file (only containing a manifest and services)
is created.</p>

<p>(The Jar task is a shortcut for specifying the manifest file of a JAR file.
The same thing can be accomplished by using the <i>fullpath</i>
attribute of a zipfileset in a Zip task. The one difference is that if the
<i>manifest</i> attribute is not specified, the Jar task will
include an empty one for you.)</p>

<p>Manifests are processed by the Jar task according to the
<a target="_blank" href="http://docs.oracle.com/javase/7/docs/technotes/guides/jar/jar.html">Jar file specification.</a>
Note in particular that this may result in manifest lines greater than 72 bytes
being wrapped and continued on the next line.</p>

<p>The Jar task checks whether you specified package information according to the
<a target="_blank" href="http://docs.oracle.com/javase/7/docs/technotes/guides/versioning/spec/versioning2.html#wp90779">
versioning specification</a>.</p>

<p><b>Please note that the zip format allows multiple files of the same
fully-qualified name to exist within a single archive. This has been
documented as causing various problems for unsuspecting users. If you wish
to avoid this behavior you must set the <code>duplicate</code> attribute
to a value other than its default, <code>"add"</code>.</b></p>

<p>To cryptographically sign your JAR file, use the <a href="signjar.html">SignJar task</a> on the JAR that you create from this task.</p>

<p>For creating a simple version of a <a target="_blank" href="http://openjdk.java.net/jeps/238">JEP-238 multi release jar</a>,
you don't need any special tools. Just set the required manifest entry and place the files where required, as you could see 
in the <a href="#jep238-example">JEP238-example</a>. If you want to tune this kind of jar, e.g. decreasing the size by deleting 
'same' classes from the versions-branches, you have to do more ...</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">destfile</td>
    <td valign="top">the JAR file to create.</td>
    <td valign="top" align="center">Yes</td>
  </tr>
  <tr>
    <td valign="top">basedir</td>
    <td valign="top">the directory from which to jar the files.</td>
    <td valign="top" align="center">No</td>
  </tr>
  <tr>
    <td valign="top">compress</td>
    <td valign="top">Not only store data but also compress them,
    defaults to true.  Unless you set the <em>keepcompression</em>
    attribute to false, this will apply to the entire archive, not
    only the files you've added while updating.</td>
    <td align="center" valign="top">No</td>
  </tr>
  <tr>
    <td valign="top">keepcompression</td>
    <td valign="top">For entries coming from existing archives (like
    nested <em>zipfileset</em>s or while updating the archive), keep
    the compression as it has been originally instead of using the
    <em>compress</em> attribute.  Defaults false.  <em>Since Ant
    1.6</em></td>
    <td align="center" valign="top">No</td>
  </tr>
  <tr>
    <td valign="top">encoding</td>
    <td valign="top">The character encoding to use for filenames
      inside the archive.  Defaults to UTF8. <strong>It is not
      recommended to change this value as the created archive will
      most likely be unreadable for Java otherwise.</strong>
      <br/>See also the <a href="zip.html#encoding">discussion in the
      zip task page</a></td>
    <td align="center" valign="top">No</td>
  </tr>
  <tr>
    <td valign="top">filesonly</td>
    <td valign="top">Store only file entries, defaults to false</td>
    <td align="center" valign="top">No</td>
  </tr>
  <tr>
    <td valign="top">includes</td>
    <td valign="top">comma- or space-separated list of patterns of files that must be
      included. All files are included when omitted.</td>
    <td valign="top" align="center">No</td>
  </tr>
  <tr>
    <td valign="top">includesfile</td>
    <td valign="top">the name of a file. Each line of this file is
      taken to be an include pattern</td>
    <td valign="top" align="center">No</td>
  </tr>
  <tr>
    <td valign="top">excludes</td>
    <td valign="top">comma- or space-separated list of patterns of files that must be
      excluded. No files (except default excludes) are excluded when omitted.</td>
    <td valign="top" align="center">No</td>
  </tr>
  <tr>
    <td valign="top">excludesfile</td>
    <td valign="top">the name of a file. Each line of this file is
      taken to be an exclude pattern</td>
    <td valign="top" align="center">No</td>
  </tr>
  <tr>
    <td valign="top">defaultexcludes</td>
    <td valign="top">indicates whether default excludes should be used or not
      (&quot;yes&quot;/&quot;no&quot;). Default excludes are used when omitted.</td>
    <td valign="top" align="center">No</td>
  </tr>
  <tr>
    <td valign="top">manifest</td>
    <td valign="top">the manifest file to use.  This can be either the location of a manifest, or the name of a jar added through a fileset.  If its the name of an added jar, the task expects the manifest to be in the jar at META-INF/MANIFEST.MF</td>
    <td valign="top" align="center">No</td>
  </tr>
  <tr>
    <td valign="top">filesetmanifest</td>
    <td valign="top">behavior when a Manifest is found in a zipfileset or zipgroupfileset file is found.  Valid values are &quot;skip&quot;, &quot;merge&quot;, and &quot;mergewithoutmain&quot;.  &quot;merge&quot; will merge all of the manifests together, and merge this into any other specified manifests.  &quot;mergewithoutmain&quot; merges everything but the Main section of the manifests.  Default value is &quot;skip&quot;.
    </td>
    <td valign="top" align="center">No</td>
  </tr>
  <tr>
    <td valign="top">update</td>
    <td valign="top">indicates whether to update or overwrite
      the destination file if it already exists.  Default is &quot;false&quot;.</td>
    <td valign="top" align="center">No</td>
  </tr>
  <tr>
    <td valign="top">whenmanifestonly</td>
    <td valign="top">behavior when no files match.  Valid values are &quot;fail&quot;, &quot;skip&quot;, and &quot;create&quot;.  Default is &quot;create&quot;.</td>
    <td valign="top" align="center">No</td>
  </tr>
  <tr>
    <td valign="top">duplicate</td>
    <td valign="top">behavior when a duplicate file is found.  Valid values are &quot;add&quot;, &quot;preserve&quot;, and &quot;fail&quot;.  The default value is &quot;add&quot;.  </td>
    <td valign="top" align="center">No</td>
  </tr>
  <tr>
    <td valign="top">index</td>
    <td valign="top">whether to create an <A
    HREF="http://docs.oracle.com/javase/7/docs/technotes/guides/jar/jar.html#JAR_Index">index
    list</A> to speed up classloading.  This is a JDK 1.3+ specific
    feature.  Unless you specify additional jars with nested <a
    href="#indexjars"><code>indexjars</code></a> elements, only the
    contents of this jar will be included in the index.  Defaults to
    false.</td>
    <td valign="top" align="center">No</td>
  </tr>
  <tr>
    <td valign="top">indexMetaInf</td>
    <td valign="top">whether to include META-INF and its children in
      the index.  Doesn't have any effect if <em>index</em> is
      false.<br/>
      Sun's jar implementation used to skip the META-INF directory and
      Ant followed that example.  The behavior has been changed with
      <a href="https://bugs.openjdk.java.net/browse/JDK-4408526">Java
      5</a>.  In order to avoid problems with Ant generated jars on
      Java 1.4 or earlier Ant will not include META-INF unless
      explicitly asked to.<br/>
      <em>Ant 1.8.0</em> - Defaults to false.</td>
    <td valign="top" align="center">No</td>
  </tr>
  <tr>
    <td valign="top">manifestencoding</td>
    <td valign="top">The encoding used to read the JAR manifest, when
      a manifest file is specified.  The task will always use UTF-8
      when writing the manifest.</td>
    <td valign="top" align="center">No, defaults to the platform encoding.</td>
  </tr>
  <tr>
    <td valign="top">roundup</td>
    <td valign="top">Whether the file modification times will be
    rounded up to the next even number of seconds.<br>
    Zip archives store file modification times with a granularity of
    two seconds, so the times will either be rounded up or down.  If
    you round down, the archive will always seem out-of-date when you
    rerun the task, so the default is to round up.  Rounding up may
    lead to a different type of problems like JSPs inside a web
    archive that seem to be slightly more recent than precompiled
    pages, rendering precompilation useless.<br>
    Defaults to true.  <em>Since Ant 1.6.2</em></td>
    <td align="center" valign="top">No</td>
  </tr>
  <tr>
    <td valign="top">level</td>
    <td valign="top">Non-default level at which file compression should be
    performed. Valid values range from 0 (no compression/fastest) to 9
    (maximum compression/slowest). <em>Since Ant 1.7</em></td>
    <td valign="top" align="center">No</td>
  </tr>
  <tr>
    <td valign="top">strict</td>
    <td valign="top">Configures how to handle breaks of the packaging version
    specification: <ul>
    <li><b>fail</b> = throws a BuildException</li>
    <li><b>warn</b> = logs a message on warn level</li>
    <li><b>ignore</b> = logs a message on verbose level (default)</li>
    </ul>
    <em>Since Ant 1.7.1</em></td>
    <td valign="top" align="center">No, defaults to <tt>ignore</tt>. </td>
  </tr>
  <tr>
    <td valign="top">preserve0permissions</td>
    <td valign="top">when updating an archive or adding entries from a
    different archive Ant will assume that a Unix permissions value of
    0 (nobody is allowed to do anything to the file/directory) means
    that the permissions haven't been stored at all rather than real
    permissions and will instead apply its own default values.<br/>
    Set this attribute to true if you really want to preserve the
      original permission field.<em>since Ant 1.8.0</em>
    </td>
    <td valign="top" align="center">No, default is false</td>
  </tr>
  <tr>
    <td valign="top">useLanguageEncodingFlag</td>
    <td valign="top">Whether to set the language encoding flag if the
      encoding is UTF-8.  This setting doesn't have any effect if the
      encoding is not UTF-8.
      <em>Since Ant 1.8.0</em>.
      <br/>See also the <a href="zip.html#encoding">discussion in the
      zip task page</a></td>
    <td valign="top" align="center">No, default is true</td>
  </tr>
  <tr>
    <td valign="top">createUnicodeExtraFields</td>
    <td valign="top">Whether to create unicode extra fields to store
      the file names a second time inside the entry's metadata.
      <br>Possible values are "never", "always" and "not-encodeable"
      which will only add Unicode extra fields if the file name cannot
      be encoded using the specified encoding.
      <em>Since Ant 1.8.0</em>.
      <br/>See also the <a href="zip.html#encoding">discussion in the
      zip task page</a></td>
    <td align="center" valign="top">No, default is "never"</td>
  </tr>
  <tr>
    <td valign="top">fallbacktoUTF8</td>
    <td valign="top">Whether to use UTF-8 and the language encoding
      flag instead of the specified encoding if a file name cannot be
      encoded using the specified encoding.
      <em>Since Ant 1.8.0</em>.
      <br/>See also the <a href="zip.html#encoding">discussion in the
      zip task page</a></td>
    <td align="center" valign="top">No, default is false</td>
  </tr>
  <tr>
    <td valign="top">mergeClassPathAttributes</td>
    <td valign="top">Whether to merge the Class-Path attributes found
      in different manifests (if merging manifests).  If false, only
      the attribute of the last merged manifest will be preserved.
      <em>Since Ant 1.8.0</em>.
      <br/>unless you also set flattenAttributes to true this may
      result in manifests containing multiple Class-Path attributes
      which violates the manifest specification.</td>
    <td align="center" valign="top">No, default is false</td>
  </tr>
  <tr>
    <td valign="top">flattenAttributes</td>
    <td valign="top">Whether to merge attributes occurring more than
      once in a section (this can only happen for the Class-Path
      attribute) into a single attribute.
      <em>Since Ant 1.8.0</em>.</td>
    <td align="center" valign="top">No, default is false</td>
  </tr>
  <tr>
    <td valign="top">zip64Mode</td>
    <td valign="top">When to use Zip64 extensions for entries.  The
      possible values are "never", "always" and "as-needed".
      <em>Since Ant 1.9.1</em>.
      <br/>See also the <a href="zip.html#zip64">discussion in the
      zip task page</a></td>
    <td align="center" valign="top">No, default is "never"</td>
  </tr>
</table>

<h3>Nested elements</h3>
<h4>metainf</h4>
<p>The nested <code>metainf</code> element specifies a <a
href="../Types/fileset.html">FileSet</a>. All files included in this fileset will
end up in the <code>META-INF</code> directory of the jar file. If this
fileset includes a file named <code>MANIFEST.MF</code>, the file is
ignored and you will get a warning.</p>

<h4>manifest</h4>
<p>The manifest nested element allows the manifest for the Jar file to
be provided inline in the build file rather than in an external
file. This element is identical to the
<a href="manifest.html">manifest</a> task, but the file and mode
attributes must be omitted.</p>
<p>
If both an inline manifest and an external file are both specified, the
manifests are merged.
</p>

<p>When using inline manifests, the Jar task will check whether the manifest
contents have changed (i.e. the manifest as specified is different in any way
from the manifest that exists in the Jar, if it exists.
If the manifest values have changed the jar will be updated or rebuilt, as
appropriate.
</p>

<a name="indexjars"><h4>indexjars</h4></a>

<p><em>since ant 1.6.2</em></p>

<p>The nested <code>indexjars</code> element specifies a <a
href="../using.html#path">PATH like structure</a>.  Its content is
completely ignored unless you set the index attribute of the task to
true.</p>

<p>The index created by this task will contain indices for the
archives contained in this path, the names used for the archives
depend on your manifest:</p>
<ul>
  <li>If the generated jar's manifest contains no Class-Path
  attribute, the file name without any leading directory path will be
  used and all parts of the path will get indexed.</li>
  <li>If the manifest contains a Class-Path attribute, this task will
  try to guess which part of the Class-Path belongs to a given
  archive.  If it cannot guess a name, the archive will be skipped,
  otherwise the name listed inside the Class-Path attribute will be
  used.</li>
</ul>

<p>This task will not create any index entries for archives that are
  empty or only contain files inside the META-INF directory unless
  the <code>indexmetainf</code> attribute has been set
  to <code>true</code>.</p>

<a name="service"><h4>service</h4></a>

<p><em>since ant 1.7.0</em></p>

<p>
  The nested <code>service</code> element specifies a service.
  Services are described in the
  <a href="http://docs.oracle.com/javase/7/docs/technotes/guides/jar/jar.html#Service_Provider">service provider overview</a>.
  The approach is to have providers JARs include files named by the service
  provided, for example,
  META-INF/services/javax.script.ScriptEngineFactory
  which can include implementation class names, one per line (usually just one per JAR).

  The name of the
  service is set by the "type" attribute. The classname implementing
  the service is the the "provider" attribute, or it one wants to
  specify a number of classes that implement the service, by
  "provider" nested elements.
</p>
<p>
<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">type</td>
    <td valign="top">The name of the service.</td>
    <td valign="top" align="center">Yes</td>
  </tr>
  <tr>
    <td valign="top">provider</td>
    <td valign="top">
      The classname of the class implementing the service.
    </td>
    <td valign="top" align="center">Yes, unless there is a nested
      <code>&lt;provider&gt;</code> element.</td>
  </tr>
</table>
  <p>
    The provider classname is specified either by the "provider" attribute, or
    by a nested &lt;provider&gt; element, which has a single "classname" attribute.
    If a JAR file has more that one implementation of the service, a number of
    nested &lt;provider&gt; elements may be used.
  </p>
  
  
<h3>Examples</h3>

<h4>Simple</h4>
<blockquote><pre>  &lt;jar destfile=&quot;${dist}/lib/app.jar&quot; basedir=&quot;${build}/classes&quot;/&gt;</pre></blockquote>
<p>jars all files in the <code>${build}/classes</code> directory into a file
called <code>app.jar</code> in the <code>${dist}/lib</code> directory.</p>


<h4>With filters</h4>

<blockquote><pre>  &lt;jar destfile=&quot;${dist}/lib/app.jar&quot;
       basedir=&quot;${build}/classes&quot;
       excludes=&quot;**/Test.class&quot;
  /&gt;</pre></blockquote>
<p>jars all files in the <code>${build}/classes</code> directory into a file
called <code>app.jar</code> in the <code>${dist}/lib</code> directory. Files
with the name <code>Test.class</code> are excluded.</p>

<blockquote><pre>  &lt;jar destfile=&quot;${dist}/lib/app.jar&quot;
       basedir=&quot;${build}/classes&quot;
       includes=&quot;mypackage/test/**&quot;
       excludes=&quot;**/Test.class&quot;
  /&gt;</pre></blockquote>
<p>jars all files in the <code>${build}/classes</code> directory into a file
called <code>app.jar</code> in the <code>${dist}/lib</code> directory. Only
files under the directory <code>mypackage/test</code> are used, and files with
the name <code>Test.class</code> are excluded.</p>

<h4>Multiple filesets</h4>
<blockquote><pre>  &lt;jar destfile=&quot;${dist}/lib/app.jar&quot;&gt;
    &lt;fileset dir=&quot;${build}/classes&quot;
             excludes=&quot;**/Test.class&quot;
    /&gt;
    &lt;fileset dir=&quot;${src}/resources&quot;/&gt;
  &lt;/jar&gt;</pre></blockquote>
<p>jars all files in the <code>${build}/classes</code> directory and also
in the <code>${src}/resources</code> directory together into a file
called <code>app.jar</code> in the <code>${dist}/lib</code> directory.
Files with the name <code>Test.class</code> are excluded.
If there are files such as <code>${build}/classes/mypackage/MyClass.class</code>
and <code>${src}/resources/mypackage/image.gif</code>, they will appear
in the same directory in the JAR (and thus be considered in the same package
by Java).</p>

<h4>Merging archives</h4>

<blockquote><pre> &lt;jar destfile="build/main/checksites.jar"&gt;
    &lt;fileset dir="build/main/classes"/&gt;
    &lt;zipfileset includes="**/*.class" src="lib/main/some.jar"/&gt;
    &lt;manifest&gt;
      &lt;attribute name="Main-Class"
            value="com.acme.checksites.Main"/&gt;
    &lt;/manifest&gt;
  &lt;/jar&gt;</pre></blockquote>
<p>
  Creates an executable jar file with a main class "com.acme.checksites.Main", and
  embeds all the classes from the jar <code>lib/main/some.jar</code>.
</p>

<blockquote><pre> &lt;jar destfile="build/main/checksites.jar"&gt;
    &lt;fileset dir="build/main/classes"/&gt;
    &lt;restrict&gt;
     &lt;name name="**/*.class"/&gt;
     &lt;archives&gt;
       &lt;zips&gt;
         &lt;fileset dir="lib/main" includes="**/*.jar"/&gt;
       &lt;/zips&gt;
     &lt;/archives&gt;
    &lt;/restrict&gt;
    &lt;manifest&gt;
      &lt;attribute name="Main-Class"
            value="com.acme.checksites.Main"/&gt;
    &lt;/manifest&gt;
  &lt;/jar&gt;</pre></blockquote>
<p>
  Creates an executable jar file with a main class "com.acme.checksites.Main", and
  embeds all the classes from all the jars in <code>lib/main</code>.
</p>

<h4>Inline manifest</h4>
<blockquote><pre>  &lt;jar destfile=&quot;test.jar&quot; basedir=&quot;.&quot;&gt;
    &lt;include name=&quot;build&quot;/&gt;
    &lt;manifest&gt;
      &lt;!-- If this is an Applet or Web Start application, include
           the proper attributes from <a href="http://docs.oracle.com/javase/7/docs/technotes/guides/jweb/index.html">http://docs.oracle.com/javase/7/docs/technotes/guides/jweb/index.html</a> --&gt;
      &lt;attribute name=&quot;Permissions&quot; value=&quot;sandbox&quot;/&gt;
      &lt;attribute name=&quot;Codebase&quot; value=&quot;example.com&quot;/&gt;
      &lt;!-- Who is building this jar? --&gt;
      &lt;attribute name=&quot;Built-By&quot; value=&quot;${user.name}&quot;/&gt;
      &lt;!-- Information about the program itself --&gt;
      &lt;attribute name=&quot;Implementation-Vendor&quot; value=&quot;ACME inc.&quot;/&gt;
      &lt;attribute name=&quot;Implementation-Title&quot; value=&quot;GreatProduct&quot;/&gt;
      &lt;attribute name=&quot;Implementation-Version&quot; value=&quot;1.0.0beta2&quot;/&gt;
      &lt;!-- details --&gt;
      &lt;section name=&quot;common/MyClass.class&quot;&gt;
        &lt;attribute name=&quot;Sealed&quot; value=&quot;false&quot;/&gt;
      &lt;/section&gt;
    &lt;/manifest&gt;
  &lt;/jar&gt;</pre></blockquote>
<p>
This is an example of an inline manifest specification including the version of the build
program (Implementation-Version). Note that the Built-By attribute will take the value of the Ant 
property ${user.name}. The manifest produced by the above would look like this:
</p>

<blockquote><pre><code>Manifest-Version: 1.0
Permissions: sandbox
Codebase: example.com
Built-By: conor
Implementation-Vendor: ACME inc.
Implementation-Title: GreatProduct
Implementation-Version: 1.0.0beta2
Created-By: Apache Ant 1.9.2

Name: common/MyClass.class
Sealed: false</code></pre></blockquote>

<h4>Service Provider</h4>

<p>
  The following shows how to create a jar file specifying a service
  with an implementation of the JDK6 scripting interface:
</p>
<blockquote><pre>&lt;jar destfile="pinky.jar"&gt;
  &lt;fileset dir="build/classes"/&gt;
  &lt;service type="javax.script.ScriptEngineFactory"
           provider="org.acme.PinkyLanguage"/&gt;
&lt;/jar&gt;
</pre></blockquote>


<p>
  The following shows how to create a jar file specifing a service
  with two implementations of the JDK6 scripting interface:
</p>
<blockquote><pre>
&lt;jar destfile="pinkyandbrain.jar"&gt;
  &lt;fileset dir="classes"/&gt;
  &lt;service type="javax.script.ScriptEngineFactory"&gt;
    &lt;provider classname="org.acme.PinkyLanguage"/&gt;
    &lt;provider classname="org.acme.BrainLanguage"/&gt;
  &lt;/service&gt;
&lt;/jar&gt;
</pre></blockquote>


<a name="jep238-example"/>
<h4>JEP238 example: a Multi-Release JAR Files</h4>
<p>
  Here we want to create a <i>Multi-Release JAR File</i> according the specification
  <a target="_blank" href="http://openjdk.java.net/jeps/238">JEP-238</a>.
  It defines on top of a JAR the possibility to place additional or overwriting classes 
  in a jar, which are available according to the Java version you run.<br> 
  Basically it sais, that you have to set the manifest entry <tt>Multi-Release: true</tt> 
  and place all additional or overwriting classes in 
  <tt>META-INF/versions/<i>number</i>/package-structure</tt>, e.g. 
  <tt>META-INF/versions/9/org/apache/ant/MyClass.class</tt>
</p>
<p>
  In this example we expect that the normal classes are compiled into
  <code>${java.classes}</code> and the Java9 classes are compiled into 
  <code>${java9.classes}</code>. 
</p>
<blockquote><pre>
    &lt;jar destfile=&quot;mrjar.jar&quot;&gt;
      &lt;manifest&gt;
        &lt;!-- special mf-entry according to the spec --&gt;
        &lt;attribute name=&quot;Multi-Release&quot; value=&quot;true&quot;/&gt;
      &lt;/manifest&gt;
      &lt;!-- directory structure according to the spec ... --&gt;
      &lt;!-- ... default classes loadable by old (&lt;Java9) versions --&gt;
      &lt;fileset dir=&quot;${java.classes}&quot;/&gt;
      &lt;!-- ... per release classes, require Java9+ for loadable via standard ClassLoader --&gt;
      &lt;zipfileset prefix=&quot;META-INF/versions/9/&quot; dir=&quot;${java9.classes}&quot;/&gt;
    &lt;/jar&gt;
</pre></blockquote>

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