Javassist

Javassist (Java Programming Assistant) is a handy class library that helps you tweak bytecodes while working on your Java projects. It’s like having a helpful sidekick when you're coding!

Easy Class Editing with Javassist

You can use Javassist to let your Java programs create new classes while they run. Plus, it lets you change a class file right when the JVM loads it. What’s cool is that it has two types of APIs: one for source level and another for bytecode level.

Source-Level API: No Bytecode Knowledge Needed

If you stick with the source-level API, you won’t need to be an expert in Java bytecode specifications to edit a class file. The entire API is designed using just Java language terms, making it super user-friendly!

On-the-Fly Compilation

You can even write in inserted bytecode as source text, and guess what? Javassist compiles it instantly! But if you prefer to dive deeper, there’s the bytecode-level API where you can edit class files directly like other editors do.

Add Methods Easily with Aspect Oriented Programming

Javassist shines when it comes to Aspect Oriented Programming (AOP). You can add new methods into a class or insert advice—like before, after, or around method calls—on both caller and callee sides.

Runtime Reflection Made Simple

An exciting application of Javassist is its ability for runtime reflection. It lets your Java programs use a metaobject that controls method calls on base-level objects without needing any fancy compiler or virtual machine!

Download Javassist Here!