This library makes java bytecode manipulation simple. it enables java programs to define a new class at runtime and to modify a class file when the jvm loads it.

unlike other bytecode editors, javassist provides two levels of api: source level and bytecode level. with the source-level api, users can edit a class file without knowledge of the specifications of the java bytecode. you can even specify inserted bytecode in the form of source text; javassist compiles it on the fly. on the other hand, the bytecode-level api allows the users to directly edit a class file as other editors.

this package includes the documentation.