Loading classes for basic information on them.

Question

Hey guys,
I'm creating a custom deployment application. Basically the developer will select all of the .class files he wants to roll out to production. They are put into a JList and then I go through them and place them in their appropriate packages to be rolled out at a future date.
The problem arises when there is a .class file that is not in the right directory structure as the package it's supposed to be in.
Translation:
Example:
the package the class is in com.test.MyPackage
But the class siting on root of C:\
What I'm hoping to accomplish is to load the class briefly enough into the JVM to get the package name of it and place it in the correct deployment directory. Remember i'm only dealing with .class files.
I have thought of decompiling and searching for the package name in a regex but then I saw URLClassLoader and ClassLoader but have had a crazy time trying to get the class loaded at all.
In Short: I won't know the package name of the file. I don't care where it's eing loaded from and I don't know where it's going to. I'm hoping I can load the class into the JVM, get the package name, and move the class to the correct package.
Thanks for your help!
Any thoughts on what I can do, even if it's totally different (programs that will do it for me, the RIGHT way I should be doing it, ETC), would be greatly appreciated.
-Ryan

Answer 1

If you are completely sure you can trust the classes not to do anything on load (and many do), you can load the class file into a byte array and pass that to a classloader to load the class, without knowing the package. But it is far safer to use a bytecode library, eg BCELimport org.apache.bcel.*;
import org.apache.bcel.classfile.*;
public class WhichPackage {
  public static void main (String[] args) {
    try {
      System.out.println(new ClassParser(args[0]).parse().getPackageName());
    } catch (Exception ex) {
      ex.printStackTrace(System.out);
}Pete