JPA Composite Primary Key

Here is an example of a composite primary key object for Hibernate/ JPA. It makes things more complicated by creating a relation from one of the pk fields to another entity. If we didn’t have this extra relation then the inner class would have another simple @Column instead.

@Entity
@Table(name="MY_TABLE" )
public class Test implements Serializable, Validatable
{
	public Test(){}

	@Id
	PK id;

        //other fields
	
	@Embeddable
	public static class PK implements Serializable{
		public PK (){}
		
		@Column (name="PK_1")
		private Long pk1;
		
		@ManyToOne(fetch=FetchType.EAGER,optional=false)
	    @JoinColumn(name="PK_2")
		private AnotherEntity ent;

		public boolean equals(Object obj) {
	        if (obj == this) return true;
	        if (obj == null) return false;
	        if (!(obj instanceof PK )) return false;
	        PK pk = (PK) obj;
	        if (pk.ent == null && pk.pk1 == null) return false;
	        return new EqualsBuilder().append(pk1, pk.pk1).append( ent, pk.ent).isEquals();
	    }

	    public int hashCode() {
	    	return new HashCodeBuilder().append(pk1).append(ent).toHashCode(); 
	    }	

		//getter/setter
	}

	//getter/setter

}

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