Loading of Properties from database in Hibernate?

Question

I have three classes having class hierarchy as

• ParentClass.java

  having commons properties used for both ChildClass1 and ChildClass2.
  

• ChildClass1 extends ParentClass

  having properties used for this ChildClass1 + it also use some of the common properties from parent class

• ChildClass2 extends ParentClass

  having properties used for this ChildClass2 + it also use some of the common properties from parent class

This all properties are available into table with two columns

**Key               value**     Type
---------------------------------------
propertyKey1    propertyValue1   Child1
propertyKey2    propertyValue2   Child1
propertyKey3    propertyValue3   Child2
propertyKey4    propertyValue4   Child2
propertyKey5    propertyValue5   CommonPorperty
..              ..               ..
propertyKeyn    propertyValuen   ..

Now I am not sure that how to load them from hibernate inheritance ?

Apology for silly question...

Thanks in advance

Answer 1

You need to put an additional column 'Discriminator' to inform Hibernate which instance should be loaded when you're working on same table with multiple types. See example:

@Entity
@org.hibernate.annotations.Entity(dynamicInsert = true, dynamicUpdate = true)
@Table(name = "PARENT_TABLE")
@DiscriminatorColumn(name = "TYPE", discriminatorType = DiscriminatorType.INTEGER)
public abstract class ParentEntity implements java.io.Serializable {

    private long id;
    private String commonValue1;

    @Id      
    @Column(name = "ID", nullable = false)
    public long getId() {
        return id;
    }

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

    @Column(name = "Common_Value1")
    public String getCommonValue1(){
        return commonValue1;
    }

    public void setCommonValue1(String commonValue1){
        this.commonValue1 = commonValue1;
    }
}


@Entity
@DiscriminatorValue("1")
public class ChildEntity1 extends ParentEntity {

    private String child1Value;

    @Column(name = "Child1_Value")
    public String getChild1Value(){
        return child1Value;
    }

    public void setChild1Value(String child1Value){
        this.child1Value = child1Value;
    }
}

@Entity
@DiscriminatorValue("2")
public class ChildEntity2 extends ParentEntity {

    private String child2Value;

    @Column(name = "Child2_Value")
    public String getChild2Value(){
        return child2Value;
    }

    public void setChild2Value(String child2Value){
        this.child2Value = child2Value;
    }
}