Add version to Jar packaging

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Add version to Jar packagingTag(s): Environment

Let's say we have the following class (package is mandatory)

package com.rgagnon;public class Hello { public static void main(String[] args) {    new Hello().say("Hello World!");    }  public void say(String s) {    System.out.println(s); }}

First create a MANIFEST.MF file :

Manifest-Version: 1.0Main-Class: com.rgagnon.Hello

Then build the executable Jar and run it.

>jar cvfm hello.jar MANIFEST.MF com\rgagnon\Hello.class>java -jar hello.jarHello World!

Now modify the manifest to include versioning information.

Manifest-Version: 1.0Main-Class: com.rgagnon.HelloSpecification-Version: 2.1Implementation-Version: 1.1

Modify the class to display the version.

package com.rgagnon;public class Hello { public static void main(String[] args) {    new Hello().say("Hello World!");    }  Hello() {   Package p = this.getClass().getPackage();   System.out.println("Hello Specification Version : "                          + p.getSpecificationVersion());   System.out.println("Hello Implementation Version : "                          + p.getImplementationVersion()); }  public void say(String s) {    System.out.println(s); }}

Compile and rebuild the Jar and execute

> jar cvfm hello.jar MANIFEST.MF com\rgagnon\Hello.class> java -jar hello.jarSpecification Version : 2.1Implementation Version : 1.1Hello World!

See also this Howto.

This example opens a given Jar and outputs its version information.

package com.rgagnon.howto;import java.util.jar.*;public class JarUtils {  public static String getJarImplementationVersion(String jar)       throws java.io.IOException  {    JarFile jarfile = new JarFile(jar);    Manifest manifest = jarfile.getManifest();    Attributes att = manifest.getMainAttributes();    return att.getValue("Implementation-Version");  }  public static String getJarSpecificationVersion(String jar)       throws java.io.IOException  {    JarFile jarfile = new JarFile(jar);    Manifest manifest = jarfile.getManifest();    Attributes att = manifest.getMainAttributes();    return att.getValue("Specification-Version");  }  public static void main(String[] args) throws java.io.IOException{    String javaMailJar = "C:/Program Files/Java/jre1.5.0/lib/mail.jar";    System.out.println("Specification-Version: "         + JarUtils.getJarSpecificationVersion(javaMailJar));    System.out.println("Implementation-Version: "         + JarUtils.getJarImplementationVersion(javaMailJar));    /*     * output :     *      Specification-Version: 1.3     *      Implementation-Version: 1.3.1     */  }}

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