C M P   2 . 0  

As noted in the previous section, with a foreign key mapping the key fields declared in the 

ejb relationship role are added to the table of the related entity. If the key fields element is 

empty, a foreign key will not be created for the entity. In a one to many relationship, the 

many side (Gangster in the example) must have an empty key fields element, and the one 

side (Organization in the example) must have a key fields mapping. In one to one 

relationships, one or both roles can have foreign keys.  

The foreign key mapping is not dependent on the direction of the relationship. This means 

that in a one to one unidirectional relationship (only one side has an accessor) one or both 

roles can still have foreign keys. 

The complete foreign key mapping for the Organization Gangster relationship follows: 

         Organization Gangster 

org has gangsters 

name

organization

gangster belongs to org 

Listing 9 10, The jbosscmp jdbc.xml Foreign Key Mapping 

R e l a t i o n   t a b l e   M a p p i n g  

Relation table mapping is less common for one to one and one to many relationships, but is 

the only mapping style allowed for many to many relationships. The relation table mapping 

for  the Gangster Job relationship follows: 

         Gangster Jobs 

93