Implementing a One-to-One Self Relationship

Some object models require a class to reference another instance of the same class. In the advanced tutorial, the Manager attribute in the Employee class references another employee (see Figure B-1).

To map the manager attribute:

1. 
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   Select the Employee's manager attribute in the Navigator pane, then click the One-to-One Mapping button on the mapping toolbar.

   The Editor pane displays the appropriate information for a one-to-one relationship to be specified.

2. Use the Reference Descriptor drop-down list on the General tab to choose Employee as the reference descriptor.

1. Select the Use Indirection option. See "Implementing Indirection in the Tutorial".

2. Click the Table Reference tab.

1. Create a new table reference by clicking the New button.

2. In the New Reference dialog box, create a reference whose:

   • Name is EMPLOYEE_EMPLOYEE

   • Source table is EMPLOYEE

   • Target database is EMPLOYEE

     
     

     Note: If you leave the Name field blank, then TopLink automatically names the table as <SourceTable>_<TargetTable>.

     
     

3. Select EMPLOYEE_EMPLOYEE (created in step 0 from the Table Reference drop-down list.

4. Click the Add button to define the foreign key fields.

   • In the Source Field column, choose MANAGER_ID (foreign key) field.

   • In the Target Field column, choose EMP_ID (primary key) field.

   • Leave the Target Foreign Key option unchecked.

     
     

     Note: The mapping is from the EMPLOYEE table, MANAGER_ID field to the EMP_ID field.

     
     

5. 
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   Click Save on the toolbar or choose File >  Save Project to save the project.