Hibernate - how to compose MANAGER-EMPLOYEE association? (newbie)

[Adrian Burlington]

Hi,

Using Hibernate I wonder how can I solve this issue: I have a table of USER, some are employees some are managers. Managers have a NULL value in the MANAGER_ID (I over simplify this issue on purpose).

Q: what should be the relationship in the POJO for USER so when I select a USER with NULL value - I will be able to get a list of all employees
AND when selecting an employee - I can get the Manager.

A MANAGER_ID is a USER_ID (see example below)

    

public class User implements Serializable
{
	@Id
	@Column(name = "USER_ID", updatable = false, nullable = false)
	private Long userID;
	    
	@Column(name = "DOB", length = 500)
	private String dob;

        //this is the place I'm not sure I do it correctly 
    @ManyToOne
    @JoinColumn(name="MANAGER_ID", nullable = true)
	private User manager;

    @OneToMany (mappedBy="manager")
    @Column(name="USER_ID")
	private List<User> empls = new ArrayList< User>();
              
}

[Cameron Wallace McKenzie]

I think you may have lurked into the muddy waters of Hibernate Inheritance Mapping.

How to map Inheritance with Hibernate and JPA: Tutorial

You have an 'is-a' as opposed to a 'has-a' relationship there. So, I think you'll need inheritance.

-Cameron

[Rahul Babbar]

I think your entity should have a field name manager of type User which should be nullable and it should have one to one association with the User entity and ofcourse your manager field will NOT be unique.(Such type of Joins are called Self Joins in SQL)

[Adrian Burlington]

  
@Entity 
@Inheritance(strategy=InheritanceType.SINGLE_TABLE) 
  

solved!
Thank you guys.