Dumping Java Class Files
I wrote some code a while back to dump out Java class files
(actually to parse Java class files) so that I could
manipulate them in mysterious ways. Basically before I left
Sun I was working on a least privilege security model for
Java and I needed to write a class loader that could return
a 'neutered' class to an untrusted application, this code
was used to test out some of these ideas. Obviously it isn't
very polished but then again it's free.
One of the things these classes do are collect the class refs
in a class file. This makes it trivial to provide a complete
collection of all classes referenced by any base class by
following all of the references. If someone does this, please
mail me the result. When someone starts shipping n editor that is
programmed in Java I'll write a class to automatically add
syntax highlighting to user method and variables.
The classes are as follows (the tar file has a symantec project file
that could build them as well):
- This is the main class, it reads in a class file and parses
its contents. Set
the debug flag for verbose output.
The AttributeInfo.java class defines the class for and Attribute
in the class file. It encapsulates the method for parsing an
optional class file attribute.
MethodInfo.java defines the class for parsing method blocks.
If you want to add a disassembler like javap has, this is where
you would plug it in.
- FieldInfo.java parse fields (instance variables) in the class
- This class deals with constant pool entries.
- This is a very primitive example program that opens
a class file, reads it in, and then dumps it out. Mostly it shows
how you can use the ClassFile class.
A tar file of all of the classes is
also here, there is a Symantec cafe project file as well (I don't
know how well these things travel). You should be able to untar
the files, cd to the dumpclass directory and type
java dumpclass dumpclass.class.
The code is free for non-commercial use, if you use it in a product
you can get a non-exclusive royalty free license by sending one copy
of your product to me. License applies only to the shipped version,
does not include the right to relicense and must be renewed when
substantaially revised versions of the product are shipped.
[Copyright © 1994-2004
Charles McManis, All Rights Reserved]
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