Hibernate Inheritance - Referencing an entity annotated with @MappedSuperclass

Question

@MappedSuperclass
public abstract class AbstractBaseModel{ }

@MappedSuperclass
public class Person extends AbstractBaseModel { }

@Entity
public class APerson extends Person { }

@Entity
public class BPerson extends Person { }

@Entity
public class Course extends AbstractBaseModel { 
  @ManyToOne
  @JoinColumn(name ="person")
  private Person person;
}

Above structure will give an exception:

Caused by: org.hibernate.AnnotationException: @OneToOne or @ManyToOne on    
Course references an unknown entity: Person

It says you cannot use Person in mappings because it is not a concrete Entity. How do I achieve such an inheritance scenario?

kostja · Accepted Answer · 2013-03-19 15:47:50Z

4

Simple, you change the @MappedSuperclass annotation on Person to @Entity

Use @MappedSuperclass only where you explicitly do not want the class to be queryable, or part of a relation. @Entity everywhere else.

A good heuristic to decide is to see whether your superclass is abstract - if it is - use @MappedSuperclass, like you did on the AbstractBaseModel

edited Mar 19, 2013 at 15:47

answered Mar 19, 2013 at 15:42

kostja

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5 Comments

user706071 Over a year ago

In that case, hibernate creates only Person class. It didn't create APerson or BPerson. Person entity merged APerson and BPerson.

kostja Over a year ago

@user706071 - I am not sure what you mean. Hibernate does not generate classes. How are APerson and BPerson different from Person? Can it be that they have no additional attributes and the differences are only behavioral?

user706071 Over a year ago

APerson and BPerson classes have their own attributes other than the common ones (Person). Anyway, thanks for reply. I will use the approach you suggest. Hibernate created a table named Person merging all attributes of APerson and BPerson, and added a DTYPE attribute to distinguish subclass type. Since my APerson and BPerson are not very different, this kind of inheritance is applicable to me.

kostja Over a year ago

If they have, hibernate should be able to map them. Perhaps it is an issue with your Inheritance settings - all entities deriving from AbstractBseModel would go into a single table if you do not annotate it with a different inheritance strategy (SINGLE_TABLE is default). You could try JOINED to be sure that the additional tables are actually generated.

CodeMed Over a year ago

I have a similar question. Are you willing to help me with it? Here is the link: stackoverflow.com/questions/25252541/…

Dariusz Dudziński · Accepted Answer · 2016-06-15 05:12:38Z

0

@Entity
@Table(name="PERSON")
@Inheritance(strategy=InheritanceType.SINGLE_TABLE)
@DiscriminatorColumn(name="discriminator",discriminatorType=DiscriminatorType.STRING)
public absract class Person extends AbstractBaseModel { }

@Entity
public class APerson extends Person { }

@Entity
public class BPerson extends Person { }

@Entity
public class Course extends AbstractBaseModel { 
  @ManyToOne
  @JoinColumn(name ="person", **insertable = false, updatable = false** )
  private Person person;
}

answered Jun 15, 2016 at 5:12

Dariusz Dudziński

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