Table per subclass inheritance relationship: How to query against the Parent class without loading any subclass ??? (Hibernate)

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感动是毒
感动是毒 2020-12-05 08:57

Suppose a Table per subclass inheritance relationship which can be described bellow (From wikibooks.org - see here)

Notice Parent class is n

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  •  没有蜡笔的小新
    2020-12-05 09:43

    A workaround is described below:

    Define your Parent class as MappedSuperClass. Let's suppose the parent class is mapped To PARENT_TABLE

    @MappedSuperClass
    public abstract class AbstractParent implements Serializable {
    
        @Id
        @GeneratedValue
        private long id;
    
        @Column(table="PARENT_TABLE")        
        private String someProperty;
    
        // getter's and setter's
    
    }
    

    For each subclass, extend the AbstractParent class and define its SecondaryTable. Any persistent field defined in the parent class will be mapped to the table defined by SecondaryTable. And finally, use AttributeOverrides if needed

    @Entity
    @SecondaryTable("PARENT_TABLE")
    public class Child extends AbstractParent {
    
        private String childField;
    
        public String getChildProperty() {
            return childField;
        }
    
    }
    

    And define another Entity with the purpose of retrieving just the parent class

    @Entity
    @Table(name="PARENT_TABLE")
    @AttributeOverrides({
        @AttributeOverride(name="someProperty", column=@Column(name="someProperty"))
    })
    public class Parent extends AbstractParent {}
    

    Nothing else. See as shown above i have used just JPA specific annotations

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