Multiple writers for a field

Question

I get an error indicating that i have multiple writers for a field table_a.item_key. I have 3 classes that use this field as shown below.
@Entity @Inheritance(strategy=InheritanceType.SINGLE_TABLE) ...
@Table(name="table_a")
@DiscriminatorColumn(name="item_Type")
abstract class A {
@Id, @Column(name="item_key")
public String getItemKey(){
@Inheritance(discriminatorValue="B")
class B extends A {
@OneToOne
@JoinColumn(name="item_key", updatable=false, insertable=false)
public C getC(){
@Entity
@Table(name="table_c")
class C {
@Id, @Column(name="item_key")
public String getItemKey(){
Note that when i remove the relationship between B and C everything works fine. It looks like TopLink gets confused when a one-to-one relationship is mapped on a column used for another field.

Answer 1

In the scenario you mention (the Vendor repository), both the Phone Number and Fax Number fields are links to corresponding Qualified Lookup tables. These are inherently multi-value fields.
Just for the sake of clarity - with the exception of Measurement type fields, it is only lookup fields that can be set to have multiple values. Refer to the matrix <a href="http://help.sap.com/saphelp_mdm550/helpdata/en/1f/2ddb4203d82b78e10000000a155106/content.htm">here</a>.
Mark