Description:

Javassist (Java Programming Assistant) makes Java bytecode
manipulation simple. It is a class library for editing bytecodes in
Java; it enables Java programs to define a new class at runtime and to
modify a class file when the JVM loads it. Unlike other similar
bytecode editors, Javassist provides two levels of API: source level
and bytecode level. If the users use the source-level API, they can
edit a class file without knowledge of the specifications of the Java
bytecode. The whole API is designed with only the vocabulary of the
Java language. 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.