Difference between name and referencedColumnName in @JoinColumn annotation?

Question

@ManyToOne
@JoinColumn(name = "someValue" , referencedColumnName = "someOtherValue" )

What values are to be placed in name and referencedColumnName column if 2 tables are linked by ManyToOne association?

Answer 1

Suppose you have Two tables:

1. Department table with columns:
 a. Dept_ID (primary key)
 b. Dept_Name

2. Employee Table with following column:
  a. Emp_Id (primary key)
  b. Dept_Id_fk (foreign key)
  c. Salary

Now your join column for Employee Entity class will be

@ManyToOne
@JoinColumn(name = "Dept_Id_fk", referencedColumnName = "Dept_ID")
Department department;

So referencedColumnName means column that you are referencing to from your foreign key column.

Answer 2

How would the join column look like for oneToMany association? Here is an example:

Person table:

person_id (pk), person_name

person_reltn table:

person_reltn_id (pk), child_person_id (fk), parent_person_id (fk)

For the above tables, if I were to create the Person entity:

 class Person(){
    
     @Id
      @Column(name = "PERSON_ID")
      private long personId;
    
      @NotFound(action = NotFoundAction.IGNORE)
      @OneToMany(fetch = FetchType.LAZY)
      @JoinColumn(
          name = "CHILD_PERSON_ID",
          referencedColumnName = "PERSON_ID",
          updatable = false,
          insertable = false)
      @Where(clause = "ACTIVE_IND = 1")
      @Filter(
          name = FilterConstants.END_EFFECTIVE_DATE_TIME_FILTER,
          condition = FilterConstants.END_EFFECTIVE_DATE_TIME_CONDITION)
      @Cache(usage = CacheConcurrencyStrategy.READ_ONLY)
      private final List<PersonRelation> personRelations = new ArrayList<>();
}

In the joinColumn, should the name always have the foreign key (which means the value from entity you are joining to) and the referenceColumnName should alway have the primary key on the entity? If yes, it will be the opposite of Sayantan's response above. Please let me know if I misunderstood the concept.

Update on 03/04/2021

After doing more research, I found the documentation on how to set the referenceColumnName based on the entity mappings[1]. Looks like, for unidirectional OneToMany mapping, the referenced column is in the table of the source entity.

1.https://docs.jboss.org/hibernate/jpa/2.1/api/javax/persistence/JoinColumn.html