Is there a java classfile / bytecode editor to edit instructions?

Question

Is there a utility (or eclipse plugin) for editing java class files? I'd like to manipulate the bytecode of a java class file without recompiling it nor having a complete buildpath.

E.g. to rename methods, add/delete instructions, change constants etc.

The only utilities I found are:

• classeditor but it's very limited in functionality (e.g. renaming of things and manipulating instructions isn't possible).

• jbe doesn't save changes (maybe because class verifying fails - before I made any changes, although the class runs perfectly)

  (jbe initially had a classpath issue, adding the class path to the jbe.bat file helped)

Solution 1

I have not seen any byte code -> byte code frontends, but plenty backends.

I would suggest that you have a look at the many byte code manipulation libraries like javassist which allow loading byte code, manipulate it, and save it back to disk, and then write a small main that does exactly that.

Solution 2

I use reJ for editing class files directly.

It allows you to edit instructions, methods, constant pool, diff classes, and a split view with a hex editor.

It's ridiculously awesome.

Solution 3

I wrote an open source Java assembler and dissasembler you may find useful.

It lets you disassemble a classfile into human readable assembly, edit it, and then reassemble it into a class. It was originally designed for writing obfuscated crackmes, so there are a lot of obscure features it supports that many other tools don't. If you need any features it doesn't currently support, feel free to contact me and I'll see what I can do.

Solution 4

Find this list of byte code manipulation/code generation libraries helpful?

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