Migrate from cglib to ByteBuddy

In diagnosing an issue for the gradle-docker-plugin library, of which I’m the current maintainer, I’m banging my head trying to get cglib to load a class into the specified custom classloader. It creates the class/object well enough but the class itself can’t be found within the actual classloader and the code ends up throwing a ClassNotFoundException. After spending way too much time with this a colleague recommended using byte-buddy instead. Looks like a very cool library but after searching the internets I couldn’t find a “migrating from cglib to byte-buddy” doc anywhere. My apologies as I haven’t read through the docs in great length yet (due to the time sink of the above) but was just wondering if you had a doc like that so that I can convert the below groovy snippet into something for byte-buddy.

        final def delegate = dockerClientObjectFactory.create(dockerClientClassLoader, "${COMMAND_PACKAGE}.LogContainerResultCallback");
        final def enhancer = dockerClientObjectFactory.create(dockerClientClassLoader, 'net.sf.cglib.proxy.Enhancer');
        enhancer.setClassLoader(dockerClientClassLoader)
        enhancer.setSuperclass(delegate.getClass())
        enhancer.setCallback([

            invoke: { Object proxy, java.lang.reflect.Method method, Object[] args ->
                if ("onNext" == method.name && args.length && args[0]) {
                        // some crazy stuff we do here
                    }
                }
                try {
                    method.invoke(delegate, args)
                } catch (InvocationTargetException e) {
                    throw e.cause
                }
            }

        ].asType(loadClass('net.sf.cglib.proxy.InvocationHandler')))

        def callback = enhancer.create()

[raphw]

Hey, the problem you encounter is that cglib relies on its own types to work, meaning that cglib must be visible to the class loader you are injecting a class into.

There is no such guide, you are correct and I should find the time to write one some day. Let me keep this issue open for a reminder. The most used capability of cglib is probably the enhancer that you are using which should be easy enough to document.

For a rough version, there is no direct equivalent but there are several options. For you, the easiest way might even be the InvocationHandlerAdapter:

new ByteBuddy()
  .subclass(delegate.getClass())
  .method(any()).intercept(InvocationHandlerAdapter.of((proxy, method, args) -> {
    // put your code here
  }).make().load(dockerClientClassLoader);

The resulting class does not have any type dependencies outside of the JDK and the delegate class such that you should not have any issues.

[cdancy]

Very awesome and easy to understand and read. Thanks!