Default fetch type for one-to-one, many-to-one and one-to-many in Hibernate
I know the answers were correct at the time of asking the question - but since people (like me this minute) still happen to find them wondering why their WildFly 10 was behaving differently, I'd like to give an update for the current Hibernate 5.x version:
In the Hibernate 5.2 User Guide it is stated in chapter 11.2. Applying fetch strategies:
The Hibernate recommendation is to statically mark all associations lazy and to use dynamic fetching strategies for eagerness. This is unfortunately at odds with the JPA specification which defines that all one-to-one and many-to-one associations should be eagerly fetched by default. Hibernate, as a JPA provider, honors that default.
So Hibernate as well behaves like Ashish Agarwal stated above for JPA:
OneToMany: LAZY
ManyToOne: EAGER
ManyToMany: LAZY
OneToOne: EAGER
(see JPA 2.1 Spec)
To answer your question, Hibernate is an implementation of the JPA standard. Hibernate has its own quirks of operation, but as per the Hibernate docs
By default, Hibernate uses lazy select fetching for collections and lazy proxy fetching for single-valued associations. These defaults make sense for most associations in the majority of applications.
So Hibernate will always load any object using a lazy fetching strategy, no matter what type of relationship you have declared. It will use a lazy proxy (which should be uninitialized but not null) for a single object in a one-to-one or many-to-one relationship, and a null collection that it will hydrate with values when you attempt to access it.
It should be understood that Hibernate will only attempt to fill these objects with values when you attempt to access the object, unless you specify fetchType.EAGER.
It depends on whether you are using JPA or Hibernate.
From the JPA 2.0 spec, the defaults are:
OneToMany: LAZY
ManyToOne: EAGER
ManyToMany: LAZY
OneToOne: EAGER
And in hibernate, all is Lazy
UPDATE:
The latest version of Hibernate aligns with the above JPA defaults.