I heard this from some developers today who confirmed the existence, by indirect evidence, of willful tampering of Java archives by gremlins using Ant. There is speculation that they live inside their own plug-in inside WebSphere Studio Application Developer.

Developer A, we’ll call him Nick (because that’s his name), came into our room to work out some tweaks with Openmake targets. He told us all that they’d been working on some problems with runtime errors getting the dreaded Major-Minor version error: “Unsupported major.minor version 49.0.” This usually indicates that you have compiled something with a 1.5 JDK but are running it under a 1.4 JVM.

The archive they were deploying was created wholly inside a workspace managed by WebSphere Studio Application Developer (WSAD) but built by Ant using IBM JDK 1.4.2. Now, WSAD by default launches under a 1.3 JVM, so there is no hint of a simple conflict of JVM’s. They actually traced the issue down to a few class files in the deployed archive that had a 49.0 class versions by using a byte editor. So only a subset of the classes compiled by Ant were affected! But, if they created their own Jar file at the command line through the Windows command prompt using the same exact files, the Major-Minor problem didn’t appear. This means the classes were altered at the packaging step - NOT the compile step!

Harking back to my pain with multiple versions of Java over the last decade, I interrupted this fine tale and asked with a haughty tone “Is a 1.5 JDK installed anywhere on the machine?”

“Yes”, he answered, and the problem, he said, was resolved by uninstalling the 1.5 JDK. We all then had a nice knowing chuckle. Then we questioned Sun’s use of the registry in Java and how the use of the registry changed with each release, forgetting, in fact that the problem happened under an IBM JDK. We also talked about the practice of dumping of java.exe under the windows/system32 (%SYSTEM_ROOT%) directory and how that could trip you up. You never knew if it was a Microsoft java.exe or a Sun one, and if it was Sun, which one was it?

Has anyone heard of this happening before? Is it a bug with Ant? Meister uses Ant under the covers for some things, but not for the Java compile. We’ve never heard of this problem before. We are, in fact, working with Nick to roll out Meister (and the Java build services used by thousands) to Eclipse at the desktop so mysterious problems like this won’t happen in the future.