Hibernate 4.2中具有@OneToMany的性能-单向与双向

Question

I need only a unidirectional relationship OneToMany, but in Terms of performance I want to ask what is the best practice?.

I did a test with Junit, and the result with bidirectional is: 1.9s and the unidirectional code 2.4s, it seems for unidirectional needs more time

I'm using Hibernate 4.2.21

@Unidirectional 2.4s

Parent.class

@OneToMany(fetch = FetchType.LAZY, cascade = CascadeType.ALL)
@JoinColumn(name = "parentuni_id")  
private Set<ChildUni> childs;

Hibernate: select nextval ('parentuni_seq')
Hibernate: select nextval ('childuni_seq')
Hibernate: select nextval ('childuni_seq')
Hibernate: insert into parentuni (parentuni_name, parentuni_id) values (?, ?)
Hibernate: insert into childuni (childuni_name, childuni_id) values (?, ?)
Hibernate: insert into childuni (childuni_name, childuni_id) values (?, ?)
Hibernate: update childuni set parentuni_id=? where childuni_id=?
Hibernate: update childuni set parentuni_id=? where childuni_id=?

@Bidirectional 1.9s

Parent.class

@OneToMany(fetch = FetchType.LAZY, cascade = CascadeType.ALL, mappedBy = "parent")
private Set<Child> childs;

Child.class

@ManyToOne(fetch = FetchType.LAZY)
@JoinColumn(name = "parent_id", nullable = false)
private Parent parent;

Hibernate: select nextval ('parent_seq')
Hibernate: select nextval ('child_seq')
Hibernate: select nextval ('child_seq')
Hibernate: insert into parent (parent_name, parent_id) values (?, ?)
Hibernate: insert into Child (child_name, parent_id, child_id) values (?, ?, ?)
Hibernate: insert into Child (child_name, parent_id, child_id) values (?, ?, ?)

Answer 1

In Hibernate best practices , it says

Prefer bidirectional associations:

• Unidirectional associations are more difficult to query . In a large application, almost all associations must be navigable in both directions in queries.

Helpful sources : http://www.javacodegeeks.com/2011/02/hibernate-mapped-collections.html

Hope this helps.