Re: [eclipselink-users] Help with PrimaryKey usage for legacy tables

[Christopher.Mathrusse@xxxxxxxxxx]

Thank you very much! That did the trick
and made things generate correctly.

Chris...

Re: [eclipselink-users] Help with PrimaryKey usage for legacy tables

christopher delahunt

to:

EclipseLink User Discussions

09/10/2009 11:42 AM

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---

Hello,

LineItem has a composite primary key, and so requires a PK class, which
can be specified using the @IdClass annotation on the entity.  If
you 
are using the JPA 1.0 spec, it only allows basic fields to be apart of
the primary key so in addition to the ManyToOne mapping, the LineItem 
will need a String orderNo attribute that is marked as updateable=false
insertable=false (or you will get a multiple writeable mapping exception
if both are writable).  This string will need to be marked as ID,
and 
the attribute added to the Primary Key class for LineItem.

If you want to try out the future JPA 2.0 specification (EclpseLink 2.0
implements a version of the draft), it allows the ManyToOne to be marked
as an ID - so you don't need to add string in LineItem for the Order_No
column.  You will still need a primary key class for LineItem though.

Also, the mappings you have provided are not correct - the OneToMany 
mapping is defaulting to using a join table because it is missing the 
mappedby="order", and the ManyToOne LineItem->Order isn't
specifying the 
column to use and so will default to order_order_no. 

Best Regards,
Chris

cmathrusse wrote:
> I'm using EclipseLink 1.1.1 and I'm trying to map a parent-child relationship
> which exists in legacy tables. I read through the documentation but
I'm
> still a bit confused by it. 
>
> An order's primary key is a String (order_no) that is defined as unique.
> LineItems have an association to the order. The lineItem table has
the
> order_no field and a line_no. It is a combination of order_no and
line_no
> that make the PrimaryKey for the LineItem. The LineItem line_no is
not
> unique within the table but is only unique with the addition of the
> order_no.
>
> I've tried a few different ways of defining the @Id but nothing seems
to be
> quite right and the table generation is not correct. I expect the
Order to
> have an order_no column and the LineItem table to have a composite
key of
> order_no and line_no. 
>
> My objects:
>
> Order {
>                  @Id
>                  @Column(name
= "ORDER_NO", length = 12)
>                  private
String orderNo;
>
>                  @OneToMany(fetch
= FetchType.EAGER)
>                  private
java.util.List<LineItem> lineItems;
>
> ...
> }
>
> LineItem {
>                  @ManyToOne
>                  private
Order order;
>
>                  @Id
>                  @Column(name
= "LINE_NO", nullable = false)
>                  private
Integer lineNo;
> }
>
> Thanks for the help....
>   
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