Hibernate Eager vs Lazy Fetch Type

The relationships are defined through joins in database. Hibernate represents joins in the form of associations like One-to-One, One-to-Many and Many-to-One. It is required to define Fetch Type when you use any of these associations. Fetch Type decides on whether or not to load all the data belongs to associations as soon as you fetch data from parent table. Fetch type supports two types of loading: Lazy and Eager. By default, Fetch type would be Lazy.

FetchType.LAZY: It fetches the child entities lazily, that is, at the time of fetching parent entity it just fetches proxy (created by cglib or any other utility) of the child entities and when you access any property of child entity then it is actually fetched by hibernate.

FetchType.EAGER: it fetches the child entities along with parent.

Lazy initialization improves performance by avoiding unnecessary computation and reduce memory requirements.

Eager initialization takes more memory consumption and processing speed is slow.

Having said that, depends on the situation either one of these initialization can be used.

Hibernate Examples

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5. What is Session object in Hibernate?
6. List Hibernate Session interface methods.
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8. Basic Hibernate CRUD operations example.
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10. Hibernate Unidirectional One-to-One mapping using @OneToOne annotation.
11. Hibernate Eager vs Lazy Fetch Type
12. Hibernate Unidirectional One-to-Many mapping using @OneToMany annotation.
13. Hibernate Bidirectional One-to-Many mapping using @OneToMany annotation.
14. Hibernate Many-to-Many mapping example using @ManyToMany annotation.
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