@Override
        public Object invoke(Object proxy, Method method, Object[] arguments) throws Throwable {
        	// only merge calls to property getters
            if (arguments.length > 0) {
                // invoke the method on the first possibility
                for (Object source : sources) {
                    if(method.getDeclaringClass().isInstance(source)){
                    	if(method.getName().startsWith("set")){
                    		String getterMethodName = "get" + StringUtils.removeStart(method.getName(),"set");
                    		cache.remove(getterMethodName);
                    	}
                        return method.invoke(source, arguments);
                    }
                }
                throw new IllegalStateException("Can't call method " + method.getName() + " on any of the sources.");
            }

            // try to use cache
            if(cache.containsKey(method.getName())){
            	return cache.get(method.getName());
            }

            List values = new ArrayList();
            for (Object obj : sources) {
                values.add(evaluate(obj, method, arguments));
            }

            Object merged = merger.merge(values);
            cache.put(method.getName(), merged);
            return merged;
        }