Java - creating a subclass dynamically

Question

I\'d like to create a subclass programatically. I guess I have few options - Javassist, CGLib, BCEL, or ASM.

The use case is that one app\'s internals are class-oriented

Answer 1

One library that I'm particularly fond of may be used here; Bytebuddy.

Example taken directly from the landing page:

Class dynamicType = new ByteBuddy()
  .subclass(Object.class)
  .method(ElementMatchers.named("toString"))
  .intercept(FixedValue.value("Hello World!"))
  .make()
  .load(getClass().getClassLoader(), ClassLoadingStrategy.Default.WRAPPER)
  .getLoaded();

It's incredibly flexible and definitely worth checking out if you'd like to keep your hair, I personally find heavy usage of javassist can get quite ugly and messy at times, bytebuddy feels like a well needed breath of fresh air!

Rafael Winterhalter is also active on StackOverflow which makes finding out anything you're unsure of a breeze.

Edit: my apology for necroposting. Landed here when a friend linked the question and forgot to check the date.