What happens if you pass a ManyToOne relationship model to a controller without accessing the related field?

If a model with a ManyToOne relationship is passed to the controller but the related field is not accessed, the behavior depends on the fetch type:

• LAZY (lazy loading) — the related field will not be loaded from the database until it is explicitly accessed. If there is no access in the controller, the related entity's data will not be loaded, saving resources.

• EAGER (eager loading) — the related entity is loaded immediately along with the main entity, even if it is not accessed.

Thus, if the relationship is configured as LAZY and the related field is not accessed, the related entity is not loaded, which can be useful for performance optimization. However, during model serialization (e.g., to JSON), there may be a LazyInitializationException if the session is already closed and the related field is accessed.