How to Access the Manifest of Your Own Jar in Java?

Reading the Manifest of Your Own Jar

Accessing the Manifest file associated with your own class can be a challenge, especially when using getClass().getClassLoader().getResource(...). This method may return the manifest from a different .jar file if called from an applet or webstart environment.

To overcome this limitation, consider the following solutions:

1. Iterating Through Manifest URLs

Iterate through the URLs returned by getResource(...) and read them as manifests until you find the correct one:

Enumeration<URL> resources = getClass().getClassLoader()
   .getResources("META-INF/MANIFEST.MF");
while (resources.hasMoreElements()) {
     try {
       Manifest manifest = new Manifest(resources.nextElement().openStream());
       // check that this is your manifest and do what you need or get the next one
       ...
     } catch (IOException E) {
       // handle
     }
}

2. Using URLClassLoader

If getClass().getClassLoader() is an instance of java.net.URLClassLoader, you can cast it and use findResource(...):

URLClassLoader cl = (URLClassLoader) getClass().getClassLoader();
try {
   URL url = cl.findResource("META-INF/MANIFEST.MF");
   Manifest manifest = new Manifest(url.openStream());
   // do stuff with it
   ...
} catch (IOException E) {
   // handle
}

This approach has been known to return the correct manifest for applets.

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