01_SingleValueExtractor.java

interface SingleValueExtractor<I, O> {

	O extractValue(I input);

	// only invoked if invalid; Property name enough as input?
	Path.Node getNode(String property);
}

02_MultiValueExtractor.java

interface MultiValueExtractor<I, O> {

	ValueAndNodeIterator<O> extractValues(I input);

	public interface ValueAndNodeIterator<O> {

		boolean hasNext();

		O next();

		TypeVariable<?> typeVariable();

		// only invoked if invalid; Property name enough as input?
		Path.Node getNode(String property);
	}
}

03_MapExtractor.java

class MapExtractor implements MultiValueExtractor<Map, Object> {

	public ValueAndNodeIterator<Object> extractValues(Map input) {
		Set<Map.Entry<?, ?>> entrySet = input.entrySet();
		final Iterator<Map.Entry> iterator = input.entrySet().iterator();
		final TypeVariable<Class<Map>> k = Map.class.getTypeParameters()[0];
		final TypeVariable<Class<Map>> v = Map.class.getTypeParameters()[1];

		return new ValueAndNodeIterator<Object>() {

			private boolean atKey = true;
			private Map.Entry<?, ?> current;

			public boolean hasNext() {
				return iterator.hasNext();
			}

			public Object next() {
				if ( atKey ) {
					current = iterator.next();
					atKey = false;
					return current.getKey();
				}
				else {
					atKey = true;
					return current.getValue();
				}
			}

			public TypeVariable<?> typeVariable() {
				return atKey ? k : v;
			}

			public Node getNode(String property) {
				// TODO Auto-generated method stub
				return null;
			}
		};
	}
}