Reading bytecode from unloaded classes in external jarfiles

Question

In my Java application, I wish to read bytecode contents from class files that aren't actually loaded, in jar files which also aren't loaded. As in, I need to be able to take any given jarfile, and find all classes inside it, ideally. So take the following situation:

My application (which is kind of a library), is asked to 'check' a certain jar at whatever path, and is provided various patterns provided by the application using my library to find similarities (such as constant pool similarities). Therefore my library needs to go through all the jars in a class file. Obviously I could make it hardcoded or loaded from a file, but I'd much rather have it so that I can go through the bytecode of all the files in a jar to match them.

Answer 1

You should use the JarFile API and iterate over the files in it. It shouldn't be hard to do. This article might be a good start.

And as for the bytecode you could just treat each (uncompressed) class file as a byte array and calculate a hash, maybe an MD5 hash of each file and compare it to previous hash.