We have a tricky question in a project using Java & Hibernate, with a model containing bi-directional relationships.
As it's a small project with few users, few entities, and few rows involved in relationships (not more than 100 in 1-n relationships), we don't really need a 2nd level cache.
Operations done with entities are simple: inserting, removing and performing some computations with entities involving relationships loading.
Let say we have two Java entities:
Furniture. An item of furniture is in one room and a room can have many items of furniture. So
Furniture has a reference to
Room has a list of
Delete Furniture action, the easiest thing to do is to retrieve the right
Furniture, and tell the EntityManager to remove the
Furniture. But, to ensure the Java instances remain coherent, we should also remove the
Furniture instance in the list of
Furnitures in the associated
Room. Unfortunately, if the
Room instance is not loaded, a request will be done to the database for nothing if we don't have a cache.
So, what would be a better choice between:
A) Keeping it simple
- In general, no preoccupation about bilateral relationships in java instances coherence, as we don't have 2nd level cache
- Well document the fact that there is a cache per-action, so if specific computations must be done requering bilateral relationships coherence within an action, this action must take care of the coherence
- No boilerplate code for bilateral relationships coherence management needed
- No overhead of loading non-necessary entites
- If a 2nd level cache must be added, then a big effort in refactoring has to be done
B) Keeping it coherent
- Always maintain the bilateral relationship's coherence
- Enable 2nd level cache