JPA -- Inheritance with duplicate column names

Question

Hi,
I have the following problem:
I have two tables. Let's call them BASE_TABLE and CHILD_TABLE. They are mapped through Join Inheritance in Java. In other words:
@Inheritance(strategy=InheritanceType.JOINED)Let's say, the tables look like:
BASE_TABLE (
    ID NUMBER(18),
    TYPE VARCHAR2(1),
    CODE NUMBER(5))
CHILD_TABLE (
    ID NUMBER(18),
    CODE NUMBER(5),
    NAME VARCHAR2(50))Here's where the problem lies: I have duplicate column names. In my example, this is the CODE column. When mapping to Java classes, I can have something like:
@Entity
@Table(name="BASE_TABLE")
@Inheritance(strategy=InheritanceType.JOINED)
@DiscriminatorColumn(name="TYPE", discriminatorType=DiscriminatorType.STRING)
@DiscriminatorValue("0")
class BaseEntity {
    @Column(name="CODE")
    private Integer code;
    public Integer getCode_Base() {
        return code;
    public setCode_Base(Integer code) {
        this.code = code;
@Entity
@Table(name="CHILD_TABLE")
@DiscriminatorValue("1")
@PrimaryKeyJoinColumn(name="ID")
class ChildEntity extends BaseEntity {
    @Column(name="CODE")
    private Integer code;
    public Integer getCode() {
        return code;
    public setCode(Integer code) {
        this.code = code;
}The trouble is, that TopLink only handles ONE of the CODE columns. When SELECTing, it only selects the CODE column from table BASE_TABLE. When generating DML statements, again it only uses the CODE column from table BASE_TABLE.
I wasn't able to make it use BOTH columns.
Please, help. The DB design cannot be changed at the moment. However, I must find a way to make TopLink Essentials use both CODE columns, not just the one from BASE_TABLE.
Thank you in advance!
Best regards,
Bisser

Answer 1

Hi Chris,
I was under the impression, that since the attributes were private, they would be treated as two different attributes by TopLink Essentials.
Java definitely treats them as two different attributes, and not as one overriding the other. I had made sure that I could set both of them with different values (via the differently named accessors) and, indeed, both values were there. I printed them both out on the console, just to make sure. They were printed out ok, the values were indeed different.
But TopLink Essentials was ignoring one of them.
Now that you told me that I should use different names for the attributes, I did just that. And lo and behold, it worked!!! I couldn't even imagine that it would matter to TopLink what the names were, given that they were in two different entities that were mapped to two different tables, inheritance or not.
As I said, Java treats them as two completely different attributes, unlike TopLink Essentials. In future, I will know that even the attribute names matter. Thank you again.
Best regards,
Bisser