private ObjectNode toObjectNode(Tuple source) {
		ObjectNode root = mapper.createObjectNode();
		for (int i = 0; i < source.size(); i++) {
			Object value = source.getValues().get(i);
			String name = source.getFieldNames().get(i);
			if (value == null) {
				root.putNull(name);
			} else {
				root.putPOJO(name, toNode(value));
			}
		}
		return root;
	}
Converts a Tuple to JSON representation

@author David Turanski
@author Gunnar Hillert
spring-xd-tuple/src/main/java/org/springframework/xd/tuple/TupleToJsonStringConverter.java