Attributte inverse, what is it for?

gogofe · **Joined:** Tue Aug 26, 2008 4:24 pm **Posts:** 29

What is the inverse atributte for, I have read about it but I dont get to understand what this is for?

Thanks

scotchy · **Joined:** Thu Dec 13, 2007 10:49 am **Posts:** 5

Inverse is the opposite of the Many-to-one association from the object. This prevents Hibernate from sending multiple SQL updates for one change. So if you add an item B to Object As collection of Bs and save it won't make changes you must set Bs parent to A to get it to persist.

Cameron McKenzie · **Posted:** Tue Sep 09, 2008 7:44 pm

You'll also see inverse rearing its head in many-to-many relationships as well:

Code:

public class LeftManyStudent {   
  @ManyToMany
  @JoinTable(name = "join_table",  
    joinColumns = { @JoinColumn(name = "lmstudent_id")},
      inverseJoinColumns={@JoinColumn(name="rmcourse_id")})
  public List<RightManyCourse> getCourses(){return courses;} 
}

***

Code:

public class RightManyCourse {
 @ManyToMany
 @JoinTable(name = "join_table", 
joinColumns={@JoinColumn(name="rmcourse_id")}, 
inverseJoinColumns={@JoinColumn(name="lmstudent_id")})
 public List<LeftManyStudent> getStudents(){return students;}
}

Mapping many-to-many relationships with Hibernate and JPA Annotations Tutorial