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Query field created by the @OrderColumn [message #778313]

Thu, 12 January 2012 05:26

Eclipse User

I have an entity like this:

 public class A {

  @OneToMany
  @OrderColumn(name = "MYORDER")
  private List<B> bList;
  ...
 }

I need to fetch from database some B objects ordered by the created MYORDER column.

If I define a field in B like this:

public class B {

  @Column(name = "MYORDER")
  private Integer order;
  ...
 }

And I try to query with:

SELECT b FROM B b WHERE ... ORDER BY b.order

EclipseLink try to create the "MYORDER" column 2 times throwing an exception and doesn't create the B table.

I can't fetch A objects because I need to fetch some B objects belonging to different A objects (even no A objects)

How can I solve this?

Regards

Alessandro

[Updated on: Thu, 12 January 2012 05:37] by Moderator

Re: Query field created by the @OrderColumn [message #778357 is a reply to message #778313]

Thu, 12 January 2012 10:19

Eclipse User

By specifying the @OrderColumn(name = "MYORDER") on the OneToMany you are saying that the bList controls that field. I'm guessing that the error you get states that you have two writable fields, or is due to the field already existing.

If you are going to map the MYORDER field within the B object directly, you should be using the OrderBy on the collection instead of OrderColumn and maintain the collection order and the order field yourself.

Best Regards,
Chris

Re: Query field created by the @OrderColumn [message #778623 is a reply to message #778313]

Fri, 13 January 2012 09:43

Eclipse User

Hello,

If you just want the list to be returned ordered, use the @OrderBy annotation instead. OrderColumn causes the field to be controlled by the collection.

Please file a bug though, as the field should not be written twice. Instead, you should get an exception stating that the field is mapped twice (since both the collection and the basic mapping try to write to the field).

Best Regards,
Chris

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