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| <html lang="en"> |
| |
| <head> |
| <link rel="stylesheet" type="text/css" href="../stylesheets/style.css"> |
| <title>Jar Task</title> |
| </head> |
| |
| <body> |
| |
| <h2 id="jar">Jar</h2> |
| <h3>Description</h3> |
| <p>Jars a set of files.</p> |
| <p>The <var>basedir</var> 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 <var>includes</var>, <var>includesfile</var>, <var>excludes</var>, <var>excludesfile</var> |
| and <var>defaultexcludes</var> attributes. With the <var>includes</var> or <var>includesfile</var> |
| attribute you specify the files you want to have included by using patterns. The <var>exclude</var> |
| or <var>excludesfile</var> attribute is used to specify the files you want to have excluded. This is |
| also done with patterns. And finally with the <var>defaultexcludes</var> 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><fileset></code> (<var>dir</var> becomes <var>basedir</var>) as well as |
| the nested <code><include></code>, <code><exclude></code> |
| and <code><patternset></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 <code>fileset</code> |
| and <code>groupfileset</code> child elements from the <code>zip</code> task are also available in |
| the <code>jar</code> task. See the <a href="zip.html">Zip</a> task for more details and |
| examples.</p> |
| |
| <p>The <var>update</var> parameter controls what happens if the JAR file already exists. When set |
| to <q>yes</q>, the JAR file is updated with the files specified. When set to <q>no</q> (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 2 |
| seconds. If a file is less than 2 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 <var>whenmanifestonly</var> parameter controls what happens when no files, apart from the |
| manifest file, or nested services, match. If <q>skip</q>, the JAR is not created and a warning is |
| issued. If <q>fail</q>, the JAR is not created and the build is halted with an error. |
| If <q>create</q> (default), an empty JAR file (only containing a manifest and services) is |
| created.</p> |
| |
| <p>(The <code>Jar</code> task has a shortcut for specifying the manifest file of a JAR file. The |
| same thing can be accomplished by using the <var>fullpath</var> attribute of |
| a <code>zipfileset</code> in a <code>Zip</code> task. The one difference is that if |
| the <var>manifest</var> attribute is not specified, the <code>Jar</code> task will include an empty |
| one for you.)</p> |
| |
| <p>Manifests are processed by the <code>Jar</code> task according to |
| the <a href="https://docs.oracle.com/javase/8/docs/technotes/guides/jar/jar.html" target="_top">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 <code>Jar</code> task checks whether you specified package information according to |
| the <a href="https://docs.oracle.com/javase/8/docs/technotes/guides/versioning/spec/versioning2.html#wp90779" |
| target="_top">versioning specification</a>.</p> |
| |
| <p><strong>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 <var>duplicate</var> attribute to a value |
| other than its default, <q>add</q>.</strong></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 href="https://openjdk.java.net/jeps/238" target="_top">JEP |
| 238 multi-release jar</a>, you don't need any special tools. Just set the |
| required <code>manifest</code> entry and place the files where required, as you could see in |
| the <a href="#jep238-example">JEP 238 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 class="attr"> |
| <tr> |
| <th scope="col">Attribute</th> |
| <th scope="col">Description</th> |
| <th scope="col">Required</th> |
| </tr> |
| <tr> |
| <td>destfile</td> |
| <td>the JAR file to create.</td> |
| <td>Yes</td> |
| </tr> |
| <tr> |
| <td>basedir</td> |
| <td>the directory from which to jar the files.</td> |
| <td>No</td> |
| </tr> |
| <tr> |
| <td>compress</td> |
| <td>Not only store data but also compress them. Unless you set the <var>keepcompression</var> |
| attribute to <q>false</q>, this will apply to the entire archive, not only the files you've |
| added while updating.</td> |
| <td>No; defaults to <q>true</q></td> |
| </tr> |
| <tr> |
| <td>keepcompression</td> |
| <td>For entries coming from existing archives (like nested <code>zipfileset</code>s or while |
| updating the archive), keep the compression as it has been originally instead of using the |
| <var>compress</var> attribute. <em>Since Ant 1.6</em></td> |
| <td>No; defaults to <q>false</q></td> |
| </tr> |
| <tr> |
| <td>encoding</td> |
| <td>The character encoding to use for filenames inside the archive. <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>No; defaults to <q>UTF8</q></td> |
| </tr> |
| <tr> |
| <td>filesonly</td> |
| <td>Store only file entries</td> |
| <td>No; defaults to <q>false</q></td> |
| </tr> |
| <tr> |
| <td>includes</td> |
| <td>comma- or space-separated list of patterns of files that must be included</td> |
| <td>No; defaults to all (<q>**</q>)</td> |
| </tr> |
| <tr> |
| <td>includesfile</td> |
| <td>name of a file. Each line of this file is taken to be an include pattern</td> |
| <td>No</td> |
| </tr> |
| <tr> |
| <td>excludes</td> |
| <td>comma- or space-separated list of patterns of files that must be excluded</td> |
| <td>No; defaults to default excludes or none if <var>defaultexcludes</var> is <q>no</q></td> |
| </tr> |
| <tr> |
| <td>excludesfile</td> |
| <td>Name of a file. Each line of this file is taken to be an exclude pattern</td> |
| <td>No</td> |
| </tr> |
| <tr> |
| <td>defaultexcludes</td> |
| <td>indicates whether default excludes should be used or not (<q>yes|no</q>)</td> |
| <td>No; defaults to <q>yes</q></td> |
| </tr> |
| <tr> |
| <td>manifest</td> |
| <td>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 <samp>META-INF/MANIFEST.MF</samp></td> |
| <td>No</td> |
| </tr> |
| <tr> |
| <td>filesetmanifest</td> |
| <td>behavior when a manifest is found in a <code>zipfileset</code> |
| or <code>zipgroupfileset</code> file. Valid values are <q>skip</q>, <q>merge</q>, |
| and <q>mergewithoutmain</q>. <q>merge</q> will merge all of the manifests together, and merge |
| this into any other specified manifests. <q>mergewithoutmain</q> merges everything but the |
| Main section of the manifests. |
| </td> |
| <td>No; defaults to <q>skip</q></td> |
| </tr> |
| <tr> |
| <td>update</td> |
| <td>indicates whether to update or overwrite the destination file if it already exists</td> |
| <td>No; defaults to <q>false</q></td> |
| </tr> |
| <tr> |
| <td>whenmanifestonly</td> |
| <td>behavior when no files match. Valid values are <q>fail</q>, <q>skip</q>, |
| and <q>create</q>.</td> |
| <td>No; defaults to <q>create</q></td> |
| </tr> |
| <tr> |
| <td>duplicate</td> |
| <td>behavior when a duplicate file is found. Valid values are <q>add</q>, <q>preserve</q>, |
| and <q>fail</q>.</td> |
| <td>No; defaults to <q>add</q></td> |
| </tr> |
| <tr> |
| <td>index</td> |
| <td>whether to create |
| an <a href="https://docs.oracle.com/javase/8/docs/technotes/guides/jar/jar.html#JAR_Index" |
| target="_top">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.</td> |
| <td>No; defaults to <q>false</q></td> |
| </tr> |
| <tr> |
| <td>indexMetaInf</td> |
| <td>whether to include <samp>META-INF</samp> and its children in the index. Doesn't have any |
| effect if <var>index</var> is <q>false</q>.<br/>Sun's jar implementation used to skip |
| the <samp>META-INF</samp> directory and Ant followed that example. The behavior has been |
| changed with <a href="https://bugs.openjdk.java.net/browse/JDK-4408526" target="_top">Java |
| 5</a>. In order to avoid problems with Ant generated jars on Java 1.4 or earlier Ant will not |
| include <samp>META-INF</samp> unless explicitly asked to. <em>Since Ant 1.8.0</em></td> |
| <td>No; defaults to <q>false</q></td> |
| </tr> |
| <tr> |
| <td>manifestencoding</td> |
| <td>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>No; defaults to default JVM character encoding</td> |
| </tr> |
| <tr> |
| <td>roundup</td> |
| <td>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 2 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. <em>Since Ant 1.6.2</em></td> |
| <td>No; defaults to <q>true</q></td> |
| </tr> |
| <tr> |
| <td>level</td> |
| <td>Non-default level at which file compression should be performed. Valid values range |
| from <q>0</q> (no compression/fastest) to <q>9</q> (maximum compression/slowest). <em>Since |
| Ant 1.7</em></td> |
| <td>No</td> |
| </tr> |
| <tr> |
| <td>strict</td> |
| <td>Configures how to handle breaks of the packaging version specification: |
| <ul> |
| <li><q>fail</q> = throws a BuildException</li> |
| <li><q>warn</q> = logs a message on warn level</li> |
| <li><q>ignore</q> = logs a message on verbose level (default)</li> |
| </ul><em>Since Ant 1.7.1</em></td> |
| <td>No; defaults to <q>ignore</q></td> |
| </tr> |
| <tr> |
| <td>preserve0permissions</td> |
| <td>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 <q>true</q> if you really want to |
| preserve the original permission field. <em>since Ant 1.8.0</em> |
| </td> |
| <td>No; defaults to <q>false</q></td> |
| </tr> |
| <tr> |
| <td>useLanguageEncodingFlag</td> |
| <td>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>No; defaults to <q>true</q></td> |
| </tr> |
| <tr> |
| <td>createUnicodeExtraFields</td> |
| <td>Whether to create Unicode extra fields to store the file names a second time inside the |
| entry's metadata.<br/>Possible values are <q>never</q>, <q>always</q> |
| and <q>not-encodeable</q> which will only add Unicode extra fields if the file name |
| cannot.<br/>See also the <a href="zip.html#encoding">discussion in the zip task page</a></td> |
| <td>No; defaults to <q>never</q></td> |
| </tr> |
| <tr> |
| <td>fallbacktoUTF8</td> |
| <td>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>No; defaults to <q>false</q></td> |
| </tr> |
| <tr> |
| <td>mergeClassPathAttributes</td> |
| <td>Whether to merge the <code>Class-Path</code> attributes found in different manifests (if |
| merging manifests). If <q>false</q>, only the attribute of the last merged manifest will be |
| preserved. <em>Since Ant 1.8.0</em>.<br/>Unless you also set <var>flattenAttributes</var> |
| to <q>true</q>, this may result in manifests containing multiple <code>Class-Path</code> |
| attributes which violates the manifest specification.</td> |
| <td>No; defaults to <q>false</q></td> |
| </tr> |
| <tr> |
| <td>flattenAttributes</td> |
| <td>Whether to merge attributes occurring more than once in a section (this can only happen for |
| the <code>Class-Path</code> attribute) into a single attribute. <em>Since Ant |
| 1.8.0</em>.</td> |
| <td>No; defaults to <q>false</q></td> |
| </tr> |
| <tr> |
| <td>zip64Mode</td> |
| <td>When to use Zip64 extensions for entries. The possible values |
| are <q>never</q>, <q>always</q> and <q>as-needed</q>. <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>No; defaults to <q>never</q></td> |
| </tr> |
| </table> |
| |
| <h3>Parameters specified as 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 <samp>META-INF</samp> directory of the jar file. If this fileset includes a file |
| named <samp>MANIFEST.MF</samp>, the file is ignored and you will get a warning.</p> |
| |
| <h4>manifest</h4> |
| <p>The nested <code>manifest</code> 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 <var>file</var> and <var>mode</var> |
| 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 <code>Jar</code> 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> |
| |
| <h4 id="indexjars">indexjars</h4> |
| |
| <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 <var>index</var> attribute of |
| the task to <q>true</q>.</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 <code>Class-Path</code> 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 <code>Class-Path</code> attribute, this task will try to guess |
| which part of the <code>Class-Path</code> belongs to a given archive. If it cannot guess a name, |
| the archive will be skipped, otherwise the name listed inside the <code>Class-Path</code> |
| 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 <samp>META-INF</samp> directory unless the <var>indexmetainf</var> attribute has been set |
| to <q>true</q>.</p> |
| |
| <h4 id="indexjarsmapper">indexjarsmapper</h4> |
| |
| <p><em>Since Ant 1.10.9</em></p> |
| |
| <p>The nested <code>indexjarsmapper</code> element can be used to perform custom filename |
| transformations for the archives specified by <code>indexjars</code> if the |
| <a href="#indexjars">default filename transformation</a> doesn't suffice. |
| |
| <h4 id="service">service</h4> |
| |
| <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="https://docs.oracle.com/javase/8/docs/technotes/guides/jar/jar.html#Service_Provider" |
| target="_top">service provider overview</a>. The approach is to have providers JARs include files |
| named by the service provided, for |
| example, <samp>META-INF/services/javax.script.ScriptEngineFactory</samp> which can include |
| implementation class names, one per line (usually just one per JAR).</p> |
| |
| <p>The name of the service is set by the <var>type</var> attribute. The classname implementing the |
| service is the the <var>provider</var> attribute, or if one wants to specify a number of classes |
| that implement the service, by <code>provider</code> nested elements.</p> |
| <table class="attr"> |
| <tr> |
| <th scope="col">Attribute</th> |
| <th scope="col">Description</th> |
| <th scope="col">Required</th> |
| </tr> |
| <tr> |
| <td>type</td> |
| <td>The name of the service.</td> |
| <td>Yes</td> |
| </tr> |
| <tr> |
| <td>provider</td> |
| <td>The classname of the class implementing the service.</td> |
| <td>Yes, unless there is a nested <code><provider></code> element.</td> |
| </tr> |
| </table> |
| <p>The provider classname is specified either by the <var>provider</var> attribute, or by a |
| nested <code><provider></code> element, which has a single <var>classname</var> attribute. If |
| a JAR file has more that one implementation of the service, a number of |
| nested <code><provider></code> elements may be used.</p> |
| |
| <h3>Examples</h3> |
| |
| <h4>Simple</h4> |
| <p>Jar all files in the <samp>${build}/classes</samp> directory into a file |
| called <samp>app.jar</samp> in the <samp>${dist}/lib</samp> directory.</p> |
| <pre><jar destfile="${dist}/lib/app.jar" basedir="${build}/classes"/></pre> |
| |
| <h4>With filters</h4> |
| |
| <p>Jar all files in the <samp>${build}/classes</samp> directory into a file |
| called <samp>app.jar</samp> in the <samp>${dist}/lib</samp> directory. Files with the |
| name <samp>Test.class</samp> are excluded.</p> |
| <pre><jar destfile="${dist}/lib/app.jar" |
| basedir="${build}/classes" |
| excludes="**/Test.class"/></pre> |
| |
| <p>Jar all files in the <samp>${build}/classes</samp> directory into a file |
| called <samp>app.jar</samp> in the <samp>${dist}/lib</samp> directory. Only files under the |
| directory <samp>mypackage/test</samp> are used, and files with the name <samp>Test.class</samp> are |
| excluded.</p> |
| <pre> |
| <jar destfile="${dist}/lib/app.jar" |
| basedir="${build}/classes" |
| includes="mypackage/test/**" |
| excludes="**/Test.class"/></pre> |
| |
| <h4>Multiple filesets</h4> |
| <p>Jar all files in the <samp>${build}/classes</samp> directory and also in |
| the <samp>${src}/resources</samp> directory together into a file called <samp>app.jar</samp> in |
| the <samp>${dist}/lib</samp> directory. Files with the name <samp>Test.class</samp> are excluded. If |
| there are files such as <samp>${build}/classes/mypackage/MyClass.class</samp> |
| and <samp>${src}/resources/mypackage/image.gif</samp>, they will appear in the same directory in the |
| jar (and thus be considered in the same package by Java).</p> |
| <pre> |
| <jar destfile="${dist}/lib/app.jar"> |
| <fileset dir="${build}/classes" |
| excludes="**/Test.class"/> |
| <fileset dir="${src}/resources"/> |
| </jar></pre> |
| |
| <h4>Merging archives</h4> |
| |
| <p>Create an executable jar file with a main class <samp>com.acme.checksites.Main</samp>, and embed |
| all the classes from the jar <samp>lib/main/some.jar</samp>.</p> |
| <pre> |
| <jar destfile="build/main/checksites.jar"> |
| <fileset dir="build/main/classes"/> |
| <zipfileset includes="**/*.class" src="lib/main/some.jar"/> |
| <manifest> |
| <attribute name="Main-Class" |
| value="com.acme.checksites.Main"/> |
| </manifest> |
| </jar></pre> |
| |
| <p>Create an executable jar file with a main class <samp>com.acme.checksites.Main</samp>, and embed |
| all the classes from all the jars in <samp>lib/main</samp>.</p> |
| <pre> |
| <jar destfile="build/main/checksites.jar"> |
| <fileset dir="build/main/classes"/> |
| <restrict> |
| <name name="**/*.class"/> |
| <archives> |
| <zips> |
| <fileset dir="lib/main" includes="**/*.jar"/> |
| </zips> |
| </archives> |
| </restrict> |
| <manifest> |
| <attribute name="Main-Class" |
| value="com.acme.checksites.Main"/> |
| </manifest> |
| </jar></pre> |
| |
| <h4>Inline manifest</h4> |
| <pre> |
| <jar destfile="test.jar" basedir="."> |
| <include name="build"/> |
| <manifest> |
| <!-- If this is an Applet or Web Start application, include |
| the proper attributes from <a href="https://docs.oracle.com/javase/8/docs/technotes/guides/jweb/index.html" target="_top">https://docs.oracle.com/javase/8/docs/technotes/guides/jweb/index.html</a> --> |
| <attribute name="Permissions" value="sandbox"/> |
| <attribute name="Codebase" value="example.com"/> |
| <!-- Who is building this jar? --> |
| <attribute name="Built-By" value="${user.name}"/> |
| <!-- Information about the program itself --> |
| <attribute name="Implementation-Vendor" value="ACME inc."/> |
| <attribute name="Implementation-Title" value="GreatProduct"/> |
| <attribute name="Implementation-Version" value="1.0.0beta2"/> |
| <!-- details --> |
| <section name="common/MyClass.class"> |
| <attribute name="Sealed" value="false"/> |
| </section> |
| </manifest> |
| </jar></pre> |
| <p>This is an example of an inline manifest specification including the version of the build program |
| (<code>Implementation-Version</code>). Note that the <code>Built-By</code> attribute will take the |
| value of the Ant property <code>user.name</code>. The manifest produced by the above would look like |
| this:</p> |
| |
| <pre> |
| 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</pre> |
| |
| <h4>Service Provider</h4> |
| |
| <p>The following shows how to create a jar file specifying a service with an implementation of the |
| JDK 6 scripting interface:</p> |
| <pre> |
| <jar destfile="pinky.jar"> |
| <fileset dir="build/classes"/> |
| <service type="javax.script.ScriptEngineFactory" |
| provider="org.acme.PinkyLanguage"/> |
| </jar></pre> |
| |
| <p>The following shows how to create a jar file specifying a service with two implementations of the |
| JDK 6 scripting interface:</p> |
| <pre> |
| <jar destfile="pinkyandbrain.jar"> |
| <fileset dir="classes"/> |
| <service type="javax.script.ScriptEngineFactory"> |
| <provider classname="org.acme.PinkyLanguage"/> |
| <provider classname="org.acme.BrainLanguage"/> |
| </service> |
| </jar></pre> |
| |
| <h4 id="jep238-example">JEP 238 example: a Multi-Release JAR Files</h4> |
| <p>Here we want to create a <em>Multi-Release JAR File</em> according the |
| specification <a href="https://openjdk.java.net/jeps/238" target="_top">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 says, that you have to set the |
| manifest entry <code>Multi-Release: true</code> and place all additional or overwriting classes |
| in <samp>META-INF/versions/<i>number</i>/package-structure</samp>, |
| e.g. <samp>META-INF/versions/9/org/apache/ant/MyClass.class</samp></p> |
| <p>In this example we expect that the normal classes are compiled into <samp>${java.classes}</samp> |
| and the Java 9 classes are compiled into <samp>${java9.classes}</samp>.</p> |
| <pre> |
| <jar destfile="mrjar.jar"> |
| <manifest> |
| <!-- special mf-entry according to the spec --> |
| <attribute name="Multi-Release" value="true"/> |
| </manifest> |
| <!-- directory structure according to the spec ... --> |
| <!-- ... default classes loadable by old (<Java 9) versions --> |
| <fileset dir="${java.classes}"/> |
| <!-- ... per release classes, require Java 9+ for loadable via standard ClassLoader --> |
| <zipfileset prefix="META-INF/versions/9/" dir="${java9.classes}"/> |
| </jar></pre> |
| |
| </body> |
| </html> |
