Empty composite values with primitive or initialized attributes can never be equivalent to null
Description
relates to
required for
Activity
Gavin KingJune 3, 2024 at 3:34 PM
I have removed the "empty embeddables" feature.
Steve EbersoleJuly 21, 2021 at 3:32 PMEdited
As composites are modeled today, this should be easy enough to follow the pattern of what is done when creating an entity mapping - it creates an instance of the entity for the purpose of getting the “initial values” for things like id, version, … We can create an instance of the embeddable and get its initial state.
In 6, there is a feature to instantiate a composite with its state, e.g. to instantiate “immutable embeddables”. That feature would not fit very well in this approach though, as we would need the arguments to pass along to the constructor. Would be better to have a more abstracted definition of whether the instance can be considered empty. CompositeType#isEmpty? CompositeType#considerNull?
CompositeCustomType (if CompositeUserType is kept in 6) would implement this to only consider null as empty.
ComponentType with a non-standard Instantiator would only consider null as empty.
ComponentType with a standard Instantiator would generally compare using the “initial values” approach
It is not a good idea to change that contract in 5 at this point - so there we’d need to decide if we want to “fix” this in 5.x.
As of HHH-7610, Hibernate should regard empty composite values and
nullas equivalent.Currently, when a composite value is compared to
nullby eitherComponentType#isEqualimplementation, each value in the empty composite it compared tonull.If the empty composite has a primitive value,
ComponentType#isEqualwill always returnfalse(because a primitive attribute cannot be null).Also, if the empty composite has an initialized value, as in the following example,
ComponentType#isEqualwill always returnfalse.If the composite has a parent attribute (e.g., mapped with
@Parent), that attribute is ignored byComponentType#isEqual.