Creating One-to-Many Mappings

With the TopLink Mapping editor, you can create both unidirectional or bidirectional one-to-many (1:M) mappings between CMP EJBs. These mappings can be either privately owned or independent.

If the one-to-many mapping is not read-only, the foreign key is stored on the target and must be updated when writing the object. This requires you to:

Define a return 1:1 mapping from the target back to the source.

Use a privately owned M:M mapping (less intrusive on your object model).
Note: In a bi-directional 1:M relationship, none of the mappings must be set to read only.

To create a one-to-many mapping:

Use this procedure to create a one-to-many mapping.

In the Structure window, select the attribute to be mapped.
- If the attribute is unmapped, the TopLink Mapping editor displays the available mappings. Select One-to-One and click Map As.
- If the attribute is currently mapped, either click the Map As button in the Structure toolbar and choose One-to-Many Mapping or right click the attribute, then choose Map As | One-to-Many.
  
  The One-to-Many Mapping - General tab appears in the TopLink Mapping editor.
  
  Figure 6-8 One-to-many mapping General Properties
Enter the required information to define this mapping.
Click the One-to-Many Mapping - Collection Options tab.
Figure 6-9 One-to-Many Mapping Collection Options
Enter the collection information for this mapping.
Click the One-to-Many Mapping - Table Reference tab.
Figure 6-10 One-to-Many Mapping Collection Options
Choose the Table Reference and foreign key(s).