Strategy for registering classes with kryo

I recently discovered the library kryonet, which is super awesome and fits my needs excellently.

However, the one problem that I am having is developing a good strategy for registering all of the classes that can be transferred.

I know that I can write a static method in each object that will return a list of all of the classes that it uses, but I would really rather not have to do that (for my own time purposes, as well as those who will be extending these objects).

I was playing around with trying to see if there was a way to get all of the classes that an object references (in it's fields as well as it's inheritance) from the getClass() method, but I was unable to have any success.

Finally, I know that kryo has kryo.setRegistrationOptional(true) but I am having a very difficult time trying to figure out how to use it. When this option is turned on, kryo still seems to throw exceptions if I haven't registered classes. Also, this method supposed is much slower than being able to register all of the classes. I'm fine if the first time you need to send an object using this method is slow, but I don't know if I'm okay with serious performance degradation every time that I want to send an object.

Ideally, I'll have a package of objects that I will want to send using kryonet. If there was just some was to scan that package and determine all of the classes that I need to register, that would be excellent. Now not all of my clients would need to register every object, but that's something of a separate issue, and I don't know if there is a solution to that.

If anyone could point me in the right direction that would be excellent.

Classes may come from different places such as disk, network, memory (dynamically generated). Therefore, obtaining information about classes to be registered with Kryo has to be handled separately for each specific case.

If you can read classes from a jar file then the following snippet should get you started.

private static List<Class<?>> getFromJarFile(final String jar, final String packageName)    throws ClassNotFoundException, IOException {
    final List<Class<?>> classes = new ArrayList<Class<?>>();
    final JarInputStream jarFile = new JarInputStream(new FileInputStream(jar));
    JarEntry jarEntry = null;
    do {
        jarEntry = jarFile.getNextJarEntry();
        if (jarEntry != null) {
            String className = jarEntry.getName();
            if (className.endsWith(".class")) {
                className = className.substring(0, className.lastIndexOf('.')); // strip filename extension
                if (className.startsWith(packageName + "/")) {  // match classes in the specified package and its subpackages       
                    classes.add(Class.forName(className.replace('/', '.')));
                }
            }
        }
    } while (jarEntry != null);
    return classes;
}