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How lazy loading is working in JPA

xsunil kumar
Ranch Hand

Joined: Dec 14, 2009
Posts: 133
Hi,

I have one doubt regarding Laxy loading of the objects in JPA. Let us suppose i have one entity Class A. A is mapped with one to many with B and B is mapped with C as Many to one. Below is sample class struture.

A {

@OneToMany(FetchType=Lazy)
private List<B> blist;
}

Class B

public class B {

@oneToMany(FetchType=Lazy)
private List<C> clist;

My question
1. B is defined as Lazy in A. Now if i will do entityManager.find(A), it will not load the data from B as due to Lazy. If i have made it Eager and they try to load entity A. then It should have to load entity of B also. Now C is defined as Lazy in B. Will it fetch data for entity C also in above case.

Regards,
sunil
Wouter Oet
Saloon Keeper

Joined: Oct 25, 2008
Posts: 2700

No it will probably will not. Remember that using the fetchtype to lazy is only a hint. It is not enforcing. The JPA provider might decide to load it anyway. If you set the fetchtype to eager then the provider must load it.


"Any fool can write code that a computer can understand. Good programmers write code that humans can understand." --- Martin Fowler
Please correct my English.
 
It is sorta covered in the JavaRanch Style Guide.
 
subject: How lazy loading is working in JPA
 
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