Composite Primary Key with @ManyToOne

Here is a fun issue that I ran into the other day while working with a legacy database.

Three tables:

Nodes

NodeID(pk)

Interfaces

InterfaceID(pk)
NodeID(fk)

InterfaceTraffic_Detail

InterfaceID(pk)
DateTime(pk)
NodeID(fk)

The InterfaceTraffic_Detail table turned out to be a little tricky for me since I have never worked with composite indexes in hibernate. It took a little trial and error but here is what I came up with

My environment is Hibernate 3.4

NmsNode.java

@Name("nmsNode")
@Entity
@Table(name="Nodes")
public class NmsNode implements Serializable {
  private static final long serialVersionUID = 1462044144509159489L;

  private int id;
  private List&lt;NmsInterface&gt; interfaces;

  @Id
  @Column(name="NodeID")
  public int getId() {
    return id;
  }

  public void setId(int id) {
    this.id = id;
  }

  @OneToMany(mappedBy="node", fetch=FetchType.LAZY)
  public List&lt;NmsInterface&gt; getInterfaces() {
    return interfaces;
  }

  public void setInterfaces(List&lt;NmsInterface&gt; interfaces) {
    this.interfaces = interfaces;
  }
}

NmsInterface.java

@Name("nmsInterface")
@Entity
@Table(name="Interfaces")
public class NmsInterface implements Serializable
{

   private static final long serialVersionUID = 1L;

   private int id;
   private NmsNode node;


   @Id
   @Column(name="InterfaceID")
   public int getId()
   {
      return id;
   }
   public void setId(int id)
   {
      this.id = id;
   }

   @ManyToOne
   @JoinColumn(name="NodeID")
   public NmsNode getNode()
   {
      return node;
   }
   public void setNode(NmsNode node)
   {
      this.node = node;
   }
}

InterfaceTraffic_Detail.java

@Entity
@Table(name="InterfaceTraffic_Detail")
@AssociationOverrides
   (
      {
           @AssociationOverride(name = "id.nmsInterface",
                 joinColumns = @JoinColumn(name = "InterfaceID"))
      }
   )
public class InterfaceTraffic_Detail implements Serializable
{
   private static final long serialVersionUID = 1L;
   private InterfaceTraffic_PrimaryKey id;
   private NmsNode nmsNode;

   @EmbeddedId
   @AttributeOverrides
   (
         {
            @AttributeOverride(name="id.dateTime", column=@Column(name="DateTime"))
         }
   )
   public InterfaceTraffic_PrimaryKey getId()
   {
      return id;
   }
   public void setId(InterfaceTraffic_PrimaryKey id)
   {
      this.id = id;
   }
   @ManyToOne
   @JoinColumn(name="NodeID")
   public NmsNode getNmsNode()
   {
      return nmsNode;
   }
   public void setNmsNode(NmsNode nmsNode)
   {
      this.nmsNode = nmsNode;
   }
}

InterfaceTraffic_PrimaryKey.java

@Embeddable
public class InterfaceTraffic_PrimaryKey implements Serializable
{
   private static final long serialVersionUID = 1L;
   private NmsInterface nmsInterface;
   private Date dateTime;

   @ManyToOne
   public NmsInterface getNmsInterface()
   {
      return nmsInterface;
   }
   public void setNmsInterface(NmsInterface nmsInterface)
   {
      this.nmsInterface = nmsInterface;
   }
   public Date getDateTime()
   {
      return dateTime;
   }
   public void setDateTime(Date dateTime)
   {
      this.dateTime = dateTime;
   }

   public int hashCode() {
      return (int) dateTime.hashCode() + nmsInterface.getId();
  }

  public boolean equals(Object obj) {
      if (obj == this) return true;
      if (obj == null) return false;
      if (!(obj instanceof InterfaceTraffic_PrimaryKey)) return false;
      InterfaceTraffic_PrimaryKey pk = (InterfaceTraffic_PrimaryKey) obj;
      return pk.nmsInterface.getId() == nmsInterface.getId() &amp;&amp; pk.dateTime.equals(dateTime);
  }
}

The important part here is the @EmbeddedId and @Embeddable on the InterfaceTraffic_Detail and InterfaceTraffic_PrimaryKey as well as the name "id.nmsInterface" on the @AssociationOverride so that I could reference the variable on the embedded class and define the @JoinColumn

Hopefully this saves someone else some time.

tags: java hibernate

Cody Lerum - January 12, 2010