Obtaining a .jar from a .exe

Question

What I'm currently dealing with is a Windows .exe that contains an executable .jar. I've tried running it through various .exe and .jar decompilers to no avail. My question is, how would I go about obtaining the .jar in the state it was in prior to being shorved into a .exe?

Please be aware, I'm not trying to convert a program from C++ or C# to java, but a .jar packed into an .exe back into a raw .jar.

Answer 1

Without knowing any information about how it was packaged into an exe, one way would be to replace the core ClassLoader in rt.jar and write the data to a file in its defineClass method. This way, whenever the classes are loaded, they will be written to respective files.

Note that this is a hack and has a ton of pitfalls. To name one, it won't include other data in jar files such as resources. Your best bet would be to find out how it was packaged like @HovercraftFullOfEels mentioned.

OpenJDK java.lang.ClassLoader source