XStream seems to have trouble with CGLIB proxies based on real classes. See following effect for a proxy extending HashMap, where the ObjectName element gets lost, that is stored in the HashMap of the DelegatingHandler:


    public class DelegatingHandler implements InvocationHandler, Serializable {
        private final Object delegate;

        public DelegatingHandler(Object delegate) {
            this.delegate = delegate;
        }

        public Object invoke(Object obj, Method method, Object[] args) throws Throwable {
            return method.invoke(delegate, args);
        }
    }

    /**
     * @throws Exception
     */
    public void testCGLib() throws Exception {
        final Enhancer enhancer = new Enhancer();
        enhancer.setSuperclass(HashMap.class);
        enhancer.setInterfaces(new Class[]{Map.class});
        enhancer.setCallback(new DelegatingHandler(new HashMap()));
        final Map orig = (Map)enhancer.create();
        orig.put("ObjectName", new ObjectName("domain:type=xy"));
        final XStream xstream = new XStream(new DomDriver());
        final String xml = xstream.toXML(orig);
        System.out.println(xml);
        final Object clone = xstream.fromXML(xml);
        System.out.println(orig);
        System.out.println(clone);
        assertEquals(orig.toString(), clone.toString());
    }