Creating Many-to-Many Mappings

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

Note: In a bi-directional M:M relationship, one mapping must be set to read-only, to prevent both mappings from writing to the relation table at the same time.

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

To create a many-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 Many-to-Many and click Map As.
- If the attribute is currently mapped, either click the Map As button in the Structure toolbar and choose Many-to-Many Mapping or right click the attribute, then choose Map As | Many-to-Many.
  
  The Many-to-Many Mapping - General tab appears in the TopLink Mapping editor.
  
  Figure 6-11 Many-to-Many Mapping General Properties
Enter the required information to define this mapping.
Click the Many-to-Many Mapping - Collection Options tab.
Figure 6-12 Many-to-Many Mapping Collection Options
Enter the collection information.
Click the Many-to-Many Mapping - Source Reference tab.
Figure 6-13 Many-to-Many Source Reference
Select the source table reference.
Click the Many-to-Many Mapping - Target Reference tab.
Figure 6-14 Many-to-Many Source Reference
Select the target table reference.