Get jar version in runtime

Question

I'm wondering if it is possible to retrieve, in runtime, a version number of a jar from which the class comes from?

I know its possible to find jar from which the class comes from:

MyClass.class.getProtectionDomain().getCodeSource().getLocation().getPath();

but what about a version?

(assuming its not in the file name:) )

yes, you are right, version belong to library version but in slang it's 'take jar version x.y.z' — 1ac0, Feb 12 '14 at 09:55
s.getClass().getPackage().getImplementationVersion() - could be null in Java 8. — Iakov Senatov, Nov 09 '18 at 08:12
to include implementation version in manifest, you have to modify the configuration element of the maven-jar-plugin and set addDefaultImplementationEntries and addDefaultSpecificationEntries to true. This will fix s.getClass().getPackage().getImplementationVersion() become null — Isuru Hemantha, Jul 31 '23 at 03:06

score 29 · Answer 1 · edited Jul 05 '16 at 06:42

29

Try this, it may be helpful:

String s = new String();
System.out.println(s.getClass().getPackage().getSpecificationVersion());
System.out.println(s.getClass().getPackage().getImplementationVersion());

Output:

1.7
1.7.0_25

edited Jul 05 '16 at 06:42

Idos

15,053
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75

answered Feb 12 '14 at 10:48

Shekhar Khairnar

2,643
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1ac0 · Accepted Answer · 2014-02-12T09:56:57.463

import javax.mail.internet.InternetAddress;

/**
Display package name and version information for javax.mail.internet.
*/
public final class ReadVersion {
  public static void main(String... aArgs){
    ReadVersion readVersion = new ReadVersion();
    readVersion.readVersionInfoInManifest();
  }

  public void readVersionInfoInManifest(){
    InternetAddress object = new InternetAddress();
    Package objPackage = object.getClass().getPackage();
    //examine the package object 
    String name = objPackage.getSpecificationTitle();
    String version = objPackage.getSpecificationVersion();
    //some jars may use 'Implementation Version' entries in the manifest instead
    System.out.println("Package name: " + name);
    System.out.println("Package version: " + version);
  }
}

If you're using maven to build the JAR, `objPackage.getSpecificationVersion()` might give 'null' as the version. to fix that, refer: https://stackoverflow.com/questions/2712970/get-maven-artifact-version-at-runtime — Isuru Hemantha, Jul 31 '23 at 03:08

score 6 · Answer 3 · answered Aug 15 '19 at 14:00

Be careful using getPackage().getImplementationVersion/getSpecificationVersion()

getSpecificationVersion returns specVersion from Manifest. Manifest is a property of a jar and is used in sun.misc.URLClassPath as

  public Manifest getManifest() throws IOException {
                    SharedSecrets.javaUtilJarAccess().ensureInitialization(JarLoader.this.jar);
                    return JarLoader.this.jar.getManifest();
                }

So in case somebody use your library as dependency for fat jar, it returns the version of Manifest for fat jar.

You have just highlighted an important reason not to make fat jars: it wipes out individual libraries’ manifest information. — VGR, Nov 20 '19 at 14:57

Get jar version in runtime

3 Answers3

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