Bundle a Java 7 .jar for Mac

Question

I created a .jar that requires Java 7. I have Java 7 (JDK and JRE) and I can double-click to run the .jar. However, I want to package this into an application.

What I tried: Using Apple's Jar Bundler tool, I successfully created an application; however, when I run it, it quickly appears and disappears in the dock. When I run the internal file JavaApplicationStub from Terminal, I get:

Exception in thread "main" java.lang.UnsupportedClassVersionError: org/lcmmun/kiosk/gui/Kiosk : Unsupported major.minor version 51.0
    at java.lang.ClassLoader.defineClass1(Native Method)
    at java.lang.ClassLoader.defineClassCond(ClassLoader.java:631)
    at java.lang.ClassLoader.defineClass(ClassLoader.java:615)
    at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:141)
    at java.net.URLClassLoader.defineClass(URLClassLoader.java:283)
    at java.net.URLClassLoader.access$000(URLClassLoader.java:58)
    at java.net.URLClassLoader$1.run(URLClassLoader.java:197)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:247)
    at java.lang.Class.forName0(Native Method)
    at java.lang.Class.forName(Class.java:247)
    at apple.launcher.LaunchRunner.loadMainMethod(LaunchRunner.java:56)
    at apple.launcher.LaunchRunner.run(LaunchRunner.java:112)
    at apple.launcher.LaunchRunner.callMain(LaunchRunner.java:51)
    at apple.launcher.JavaApplicationLauncher.launch(JavaApplicationLauncher.java:52)

which, according to "unsupportedclassversionerror unsupported major.minor version 51.0 unable to load class" means that I don't have Java 7 installed. But I do.

So my hypothesis is that JavaApplicationStub is Java 7-incompatible.

I've also heard of an ANT task to accomplish the same task, but it seemed too complicated, and I don't know how to use ANT. If this really is the solution, though, I'd be happy to learn.

EDIT: I have now also tried Eclipse's Export > Other > Mac OS Application Bundle. This fails as well.

I'm running 10.8 Mountain Lion, 64-bit.

Answer 1

Issue

You are definitely right with your assumption that Apples JavaApplicationStub located here:

• System/Library/Frameworks/JavaVM.framework/Resources/MacOS/JavaApplicationStub

is only compatible with Apples own Java Packages build for Mac OS X.

Reason

Apple is discontinuing their own Java System Packages and only supports Java 6 in their fade out process. Oracle took now over and provides Java 7 for Mac OS X from 10.7.3 on. Apple is even discontinuing developer tools like Jar Bundler.app without any notice, as you can see in this post:

• Why is Jar Bundler gone in Mac OS X Mountain Lion 10.8.2

Some people even tried desperately to manually increase the JVMVersion property value in Info.plist, read by Apples JavaApplicationStub, from a documented literal 1.6 or 1.6+ to an undocumented literal like 1.7. This won't work either and you will end up with a dialog like this, even if you have installed Oracles Java 7 Package.

So it is likely you will find other inconstancies between the retired Apple Java 6 world and the future Oracle Java 7 world.

Solution

To build an application packages based on Oracles Java 7 you need to use Oracles AppBundler Ant Task containing Oracles JavaAppLauncher. This one now only supports Oracles Java 7 for Mac OS X and isn't backwards compatible with Apples own Java System Packages.

The good news now is, you can inline Oracles Java 7 JRE into your application package. It will be contained within the directory

• Contents/PlugIns

in the application package, for example

• Contents/PlugIns/jdk1.7.0_17.jdk

This means your application package is totally self contained and ready for App Store deployment.

But you don't have to do that. You could also rely on the installed Oracle Java 7 Package.

For a more detailed answer you should also checkout:

• Application is using Java 6 from Apple instead of Java 7 from Oracle on Mac OS X?