CODEWITHSUNDEEP
javajpa
albifant
albifant

Reputation: 237

JPA Relation between classes, referring to their Interfaces

I have two classes with their respective interfaces between which I want to create a JPA @OneToOne Relation. This fails with [class EmployeeImpl] uses a non-entity [class Adress] as target entity in the relationship attribute [field adress].

First Interface / Class:

public interface Employee {
  public long getId();
  public Adress getAdress();
  public void setAdress(Adress adress);
}

@Entity(name = "EmployeeImpl")
@Table(name = "EmployeeImpl")
public class EmployeeImpl implements Employee {

  @Id
  @Column(name = "employeeId")
  @GeneratedValue(strategy = GenerationType.AUTO)
  private long id;

  @OneToOne(cascade = CascadeType.PERSIST)
  private Adress adress;

  // snip, getters and setters
}

Second Interface / Class:

public interface Adress {
  public long getId();
  public String getStreet();
  public void setStreet(String street);
}

@Entity(name = "AdressImpl")
@Table(name = "AdressImpl")
public class AdressImpl implements Adress {

  @Id
  @Column(name = "AdressId")
  @GeneratedValue(strategy = GenerationType.AUTO)
  private long id;

  @Column(name = "Street")
  private String street;

  // Snip getters and setters
}

The persistence.xml looks like this:

<?xml version="1.0" encoding="UTF-8"?>
<persistence version="2.0"
  xmlns="http://java.sun.com/xml/ns/persistence" 
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://java.sun.com/xml/ns/persistence
    http://java.sun.com/xml/ns/persistence/persistence_2_0.xsd">
    <persistence-unit name="employee"
        transaction-type="RESOURCE_LOCAL">
        <class>EmployeeImpl</class>
        <class>AdressImpl</class>
        <properties>
            <property name="eclipselink.create-ddl-jdbc-file-name"
    value="create-matterhorn-employee.jdbc" />
            <property name="eclipselink.drop-ddl-jdbc-file-name" 
    value="drop-matterhorn-employee.jdbc" />
        </properties>
    </persistence-unit>

</persistence>

I shortened out package names and imports and such. Exception occurs when trying to create the EntityManagerFactory (where you hand over the persistence unit). I am using eclipse link 2.0.2.

Upvotes: 1

Views: 337

Answers (2)

andbi
andbi

Reputation: 4454

Actually JPA does allow such interface relationships, but in this case you have to provide an entity class implementing the interface, in you case this will look as follows:

@OneToOne(targetEntity = AddressImpl.class)
private Adress adress;

Upvotes: 2

DataNucleus
DataNucleus

Reputation: 15577

JPA standard does not allow for interface fields (or Collection of interface fields) being entity relationships. Some JPA implementations do support it (e.g DataNucleus JPA), but its a vendor extension to the spec. Consequently you either use one of those implementations or change your model (or add extra annotations/XML to define what type is actually stored there).

Upvotes: 2

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