Add version to Jar packaging

From CodeCodex

[edit] Implementations

[edit] Java

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: 1.0
Main-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.jar
Hello World!

Now modify the manifest to include versioning information.


Manifest-Version: 1.0
Main-Class: com.rgagnon.Hello
Specification-Version: 2.1
Implementation-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.jar
Specification Version : 2.1
Implementation Version : 1.1
Hello 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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Category: Java