private ArrayNode toArrayNode(List<?> source) {
		ArrayNode array = mapper.createArrayNode();
		for (Object value : source) {
			if (value != null) {
				array.add(toNode(value));
			}
		}
		return array;
	}
Converts a Tuple to JSON representation

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