What is referencedColumnName used for in JPA?

Question

In JPA there is an attribute called referencedColumnName that can be set on @JoinColumn, @PrimaryKeyJoinColumn what is the idea behind this setting, can someone give a good example of where this can be used?

Answer 1

It is there to specify another column as the default id column of the other table, e.g. consider the following

TableA   id int identity   tableb_key varchar   TableB   id int identity   key varchar unique  // in class for TableA @JoinColumn(name="tableb_key", referencedColumnName="key") 

Answer 2

"referencedColumnName" property is the name of the column in the table that you are making reference with the column you are anotating. Or in a short manner: it's the column referenced in the destination table. Imagine something like this: cars and persons. One person can have many cars but one car belongs only to one person (sorry, I don't like anyone else driving my car).

Table Person
name char(64) primary key
age int

Table Car
car_registration char(32) primary key
car_brand (char 64)
car_model (char64)
owner_name char(64) foreign key references Person(name)

When you implement classes you will have something like

class Person{    ... }  class Car{     ...     @ManyToOne     @JoinColumn([column]name="owner_name", referencedColumnName="name")     private Person owner; } 

EDIT: as @searchengine27 has commented, columnName does not exist as a field in persistence section of Java7 docs. I can't remember where I took this property from, but I remember using it, that's why I'm leaving it in my example.