Unique Column names mapping a deep value type hierarchy

bob70 · **Posted:** Wed Feb 25, 2009 3:42 am

Hello,

I have a problem mapping a given (=fixed) deep class hierarchy with value type inclusion. Here is a simplified version of the problem:

Code:

@Entity class A
{
    @Id String key;
    B b;
    C c;
}

@Embeddable class B
{
    String bla;
    D d;
}

@Embeddable class C
{
    String bli;
    D d;
}

@Embeddable class D
{
    String blubber;
}

The generated table for A (annotated as shown above) would have the columns: key, bla, bli, blubber

However, for a correct mapping it would need 2 blubber columns (one for class B and one for class C content).

Do you have any idea how to annotate the D.blubber member so the resulting DB table gets 2 blubber entries (without making class D an entity type)?

Thank you,
Robert[quote][/quote]

mmerder · **Posted:** Wed Feb 25, 2009 5:14 am

You can use AttributeOverride:

Code:

@Embedded
    @AttributeOverrides( {
            @AttributeOverride(name="d.blubber", column = @Column(name="c_d_blubber") )
    } )
    C c;

The example in the annotation guide also uses embedded components in embeddables, where the attributes get overridden.

bob70 · **Posted:** Wed Feb 25, 2009 5:36 am

Thank you, mmerder! Your description would solve the problem I described; however I left out some details from my real scenario which make the topic more tricky:

The classes B, C and D are generated automatically (from a WSDL file) and are processed one-by-one by regular expressions to add the persistence annotations. So class A doesn't know anything about the content of class B or C and thus doesn't know about class D..

A solution would be to annotate class A that any column name of any attribute of class B should get a preceding 'A_' - but I don't know if this is possible at all (or how to annotate this)

mmerder · **Posted:** Wed Feb 25, 2009 5:48 am

Quote:

A solution would be to annotate class A that any column name of any attribute of class B should get a preceding 'A_' - but I don't know if this is possible at all (or how to annotate this)

You can configure hibernate to use a save naming strategy, so that it allways puts the attribute name before embedded attributes.
Set property "hibernate.ejb.naming_strategy" to "org.hibernate.cfg.DefaultComponentSafeNamingStrategy" in your hibernate.cfg.xml or persistence.xml (if using JPA).

bob70 · **Posted:** Wed Feb 25, 2009 6:09 am

Great!! Problem solved, thank you very much, mmerder!

best regards, Robert