Hibernate Creating Map<Object,List<Object>>

[Charlies]

Hello everyone,

I'm new in Grails/Hibernate and i'm trying to do a domain modeling with the following sctucture

class Object0 {

Map <Object1,List<Object2> = []

}

This is because i need that the Object 0 have a Map of Objects1 that every Object1 have diferents Object2 depending of Object0.

I'm trying to create a hasMany relationship with Objects but grails doens't accept object as Key of a map on Relationship

Map <Object1,list<Object2>> relationship
static hasMany = [relationship, Object1]

But Hibernate error say's only String can be a key of a Map.

What can i do?

Thank's

[Ian Roberts]

On 11/06/2012 15:02, Charlies wrote:
> But Hibernate error say's only String can be a key of a Map.
>
> What can i do?

Think about modelling your domain slightly differently, using a domain
class to represent the association:

class ObjectRelationship {
  Object1 o1
  Object2 o2
}

Then instead of myObject0.relatedObjects.get(someO1) you do
ObjectRelationship.findAllByO1(someO1)*.o2.  Or you can write a utility
method in Object0 itself to do this:

class Object0 {
  List<Object2> findObject2sFor(Object1 obj) {
    ObjectRelationship.withCriteria {
      eq('o1', obj)
      projections {
        // return the Object2 rather than the ObjectRelationship
        property('o2')
      }
    }
  }
}

then you can say myObject0.findObject2sFor(someO1)

Ian

--
Ian Roberts               | Department of Computer Science
[hidden email]  | University of Sheffield, UK

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[Charlies]

I thought in the possibility to create a different domain model but my application requires this specific scructure.
an Object relationship can be create easily with a couple of static hasMany relationship but i'm trying to use hibernate in all aplicacion without need to implement manually getters and setters and DDBB sctucture.

Can i create a map or list in hibernate using object as a key?

Thanks.

2012/6/11 Ian Roberts [via Grails] <[hidden email]>

On 11/06/2012 15:02, Charlies wrote:
> But Hibernate error say's only String can be a key of a Map.
>
> What can i do?

Think about modelling your domain slightly differently, using a domain
class to represent the association:

class ObjectRelationship {
  Object1 o1
  Object2 o2
}

Then instead of myObject0.relatedObjects.get(someO1) you do
ObjectRelationship.findAllByO1(someO1)*.o2.  Or you can write a utility
method in Object0 itself to do this:

class Object0 {
  List<Object2> findObject2sFor(Object1 obj) {
    ObjectRelationship.withCriteria {
      eq('o1', obj)
      projections {
        // return the Object2 rather than the ObjectRelationship
        property('o2')
      }
    }
  }
}

then you can say myObject0.findObject2sFor(someO1)

Ian

--
Ian Roberts               | Department of Computer Science
[hidden email]  | University of Sheffield, UK

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