I am managing a list of attributes in session and successfully saving the updated list for the same key in the map as long as i don't have to save an empty list. The list consists of objects of a custom class and i found it impossible to replace the list in session with an empty one or to remove the key in the map if the list is empty. Instead of replacing the object with elements, it kept it in the session until I tried to replace it with an array with at least one object. I assume that the answer is in the serialization settings, maybe the serializer ignores empty objects if empty is the object's default value or something? Thanks for the answer in advance.