Question

I have the following tables:

[ table : column1, column2 ]

A : id, name

B : id, name

AB : idA, idB

AB is a join table.

Then I have this method on hibernate class B

@OneToMany( fetch = FetchType.EAGER)
@JoinTable( name = "AB", 
            joinColumns = @JoinColumn( name = "idB"),
            inverseJoinColumns = @JoinColumn( name = "idA") )
public List<A> getAs(){
    //return the list of matching stuff
}

This works perfectly fine.

Now I want to do this sql query in hibernate:

select * from B inner join AB on B.id = AB.idB where AB.idA = 1234

Essentially, ‘list me all B’s that reference A with id 1234’

I could do straight sql, but that would defeat the purpose of getAs()

Is it possible to construct a Criterion/Restriction clause to achieve this?

Answer 1

Relationship between A and B is not one-to-many in this case, but rather many-to-many. You should map it as such:

@ManyToMany
@JoinTable(name = "AB", 
            joinColumns = @JoinColumn( name = "idB"),
            inverseJoinColumns = @JoinColumn( name = "idA") )
public List<A> getAs(){
    //return the list of matching stuff
}

Note that eagerly fetching a collection is not a good idea in most cases, hence fetch = FetchType.EAGER removed above. You can now do the same on A side to make relationship bidirectional:

@ManyToMany(mappedBy='As')
public List<B> getBs(){
    //return the list of matching stuff
}

Now getting all Bs for given A is just a matter of calling getBs() on that A instance. You can create criteria / write HQL to do that as well – from either side.