Javassist: how to create proxy of proxy?

Question

I'm creating proxies with javassist ProxyFactory. When creating a single proxy all works fine.

However, when I pass a proxied object to the proxying mechanism, it fails with

javassist.bytecode.DuplicateMemberException: duplicate method: setHandler in com.mypackage.Bean_$$_javassist_0_$$_javassist_1

I'm creating the proxies with this:

public Object createProxiedInstance(Object originalInstance) throws Exception {
    Class<?> originalClass = instance.getClass();
    ProxyFactory factory = new ProxyFactory();

    factory.setSuperclass(originalClass);

    factory.setHandler(new MethodHandler() {..});
    Class<T> proxyClass = factory.createClass();

    return proxyClass.newInstance();
}

So, how do I create proxies of proxies?

Update: The actual problems is that each proxy implements the ProxyObject which defines setHandler(..) method. So the 2nd proxy is trying to redefine the method, instead of overriding it in the subclass.

Answer 1

The problem was (actually, it's the same with CGLIB - I tried it using commons-proxy) that I should not try to create a proxy class of the proxy class. The second proxy should again be of the original class. So adding the following line resolves the problem:

if (instance instanceof ProxyObject) {
    originalClass = originalClass.getSuperclass();
}

And an advice - if you can use some sort of interceptors (like the ones defined in commons-proxy), do it instead of using multiple proxies.