Defining the order of a list

Question

I have the following problem. I have three classes, A, B and C. A contains a OneToMany relationed list of B:s. B contains a ManyToOne relation to C. C contains a field called "name" and B also contains a field called "name". What I'd like to accomplish is to have the items in A's list sorted primarily by C's name and secondarily by B's name - the problem is that I do not know how to do this. Is it even possible?

I'm using EclipseLink as my JPA provider.


class A {
   @OneToMany
   @OrderBy("b.c.name, b.name") <---- this is the problem
   List<B> b;
}

class B {
   @ManyToOne
   C c;
   String name;
}

class C {
   String name;
}

EDIT Yes, I've tried different variations, for example @OrderBy("c.name") doesn't work, I just get an error message telling me that the entity class b does not contain a field called "c.name".

score 13 · Accepted Answer · answered Jul 09 '09 at 17:29

13

It's NOT possible. @OrderBy only accepts direct property / field names, not nested properties. Which makes sense, really, because "c" table - depending on your fetching strategy may not even be part of a select issued to retrieve your "b"s.

answered Jul 09 '09 at 17:29

ChssPly76

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score 3 · Answer 2 · answered Jul 09 '09 at 22:30

3

ChssPly76 is right.

What you could do is to create a named query like this one:

 SELECT b 
 FROM B b 
 WHERE b.a = :mya 
 ORDER BY b.c.name

answered Jul 09 '09 at 22:30

Grzegorz Oledzki

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score 0 · Answer 3 · answered Jul 09 '09 at 16:50

0

Have you tried @OrderBy("c.name", "name") ?

You shouldn't use "b." because it's implied that the @OrderBy will be done on columns of the instances of B on the b array.

answered Jul 09 '09 at 16:50

Chochos

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score 0 · Answer 4 · answered Jul 09 '09 at 16:50

0

Have you tried:

 @OrderBy("c.name ASC", "name ASC")

?

answered Jul 09 '09 at 16:50

Jack Leow

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score 0 · Answer 5 · answered Jul 06 '18 at 11:12

It is not possible in javax.persistence.OrderBy (as say ChssPly76 ), but when I was using Hibernate I construct new column in PLAIN SQL with Formula() annotation and then OrderBy over it:

class A {
   @OneToMany
   @OrderBy("orderCol") <---- reference to virtual column
   List<B> b;
}

class B {
   @ManyToOne
   C c;
   String name;

   @org.hibernate.annotations.Formula(
     "( select C_table.name as orderCol from C_table where C_table.id = id )"
   ) <------------------------------------------ join with plain SQL statment
   String orderCol;
}

May be EclipseLink has same possibilities?

Defining the order of a list

5 Answers5

Linked