Hibernate: Parent/Child relationship for a single table with composite key

A similiar topic has already been covered, but without the problem of having a composite key in the table. Basically I am trying to get a hierarchy tree out of a single table, which has the following structure:

• Four columns representing the composite key
• A column containing the parent Id
• Other columns

My objective is to map a single class to this table using hibernate annotations and then build my hierarchy tree out of it:

@Entity
@Table(name = "Enti")
public class DevUnit {

    /** The valuable fields from the Ent开发者_如何学编程i table */
//  Primary Key (PK) Object
@EmbeddedId
@AttributeOverrides({
    @AttributeOverride(name = "stazione",   column = @Column(name="IdStazione")),
    @AttributeOverride(name = "categoria",  column = @Column(name="IdCategoria")),
    @AttributeOverride(name = "tipoente",   column = @Column(name="IdTipoEnte")),
    @AttributeOverride(name = "ente",       column = @Column(name="IdEnte"))
    })
private EnteDBPK EnteDBPK;

@OneToMany
@JoinColumn(name = "parentId")
private List<DevUnit> children = new ArrayList<DevUnit>();

@ManyToOne(targetEntity = DevUnit.class, optional=true, fetch=FetchType.LAZY)
@JoinColumn(name = "parenId",insertable=false,updatable=false)
private DevUnit parent = null;

// Getters and setters...
}

The EnteDBPK is my composite key, defined as:

@Embeddable
public class EnteDBPK implements Serializable {

private static final long serialVersionUID = 2960251547408481498L;

/** Fields representing the composite primary key*/
private long stazione;
private long categoria;
private long tipoente;
private long ente;


public EnteDBPK(){}

    public EnteDBPK(long stazione, long categoria, long tipoente, long ente){
        this.stazione = stazione;
        this.categoria = categoria;
        this.tipoente = tipoente;
        this.ente = ente;
    }

    // Getters and setters, equals and hashcode overrides...
}

The associations are probably not correctly defined, as I get this error when I try to run it:

org.hibernate.AnnotationException: A Foreign key refering package.DevUnit from package.DevUnit has the wrong number of column. should be 4

I'm sure I'm missing something in both the associations, but I need your help to understand the problem and find a solution to it.

Thanks for your help.

Antonio

If composite key of DevUnit consists of 4 columns, foreign key that references it should consist of 4 columns as well:

@OneToMany(mappedBy = "parent")
private List<DevUnit> children = new ArrayList<DevUnit>();

@ManyToOne(optional=true, fetch=FetchType.LAZY) 
@JoinColumns({
    @JoinColumn(name = "parentIdStazione", referencedColumnName = "IdStazione"),
    @JoinColumn(name = "parentIdCategoria", referencedColumnName = "IdCategoria"),
    @JoinColumn(name = "parentIdTipoEnte", referencedColumnName = "IdTipoEnte"),
    @JoinColumn(name = "parentIdEnte", referencedColumnName = "IdEnte")
})
private DevUnit parent = null;

Actually you can omit @JoinColumns here if default names are fine.

Also note that your approach to mapping bidirectional one-to-many/many-to-one relationship (with "one" side being the owning side) is not recommended by Hibernate documentation, so that I used another approach in the snippet above, see 2.2.5.3.1.1. Bidirectional.