You can add fields to the primary key fields of a container-managed
persistence (CMP) entity bean.
To add a field to a CMP primary key field, in
the diagram editor, right-click the field that is not a key in the
CMP entity bean; then click .
The CMP field is added to the primary key field and the
field of the CMP entity bean has an icon with a key beside it. The
CMP field also appears in the Project Explorer view
with an icon identical to the one in the diagram editor.