Hibernate：根据类型将多对一关联映射到不同的父表？

Question

I have tables which look like this:

Item table:

ItemName   Varchar2(200)
ItemId     Number
OwnerId    Number
OwnerType  number

Person table:

PersonName Varchar2(200)
PersonId   Number

Company table:

CompanyName Varchar2(200)
CompanyId   Number

When the ownerType for an Item is '1', the ownerId of the item is a foreign key PersonId of the 'person' table. When the OwnerType is '2', the ownerId is a foreign key of the CompanyId of the Company table.

I didn't do the data modelling & I don't have the option of changing the schema.

I'd like to solve two problems: (1) I'd like a mapping file for the Item table which would give me the items's owner. (2) I'd like mapping files for the Person & Company tables which would give me the Items owned by the Person or Company, respectively.

Note: a CompanyId and a PersonId can be the same number, so an item is only owned by a Person when person.personid = item.ownerid and item.ownertype = 1.

I can control the mapping files & the object diagram, so I could create an Owner interface or super-class.

Can Hibernate do this sort of thing?

Answer 1

• Case 1 : you can use the concept of Table per class hierarchy .
• Case 2 : map items as set for person/company class with where condition on the set mapping.