Revision as of 13:13, 19 April 2011

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Key API

• XmlInverseReference

Bidirectional Relationships

In order to map bidirectional relationships in EclipseLink MOXy, one of the properties must be annotated as an @XmlInverseReference, to avoid infinite loops during marshalling due to the cyclic relationship.

When binding JPA entities to XML, there are MOXy extensions will help you map a bidirectional relationship.

In this sample model, notice that Customer has a relationship to Address, and Address has a relationship back to Customer. In JPA, one direction of the relationship is mapped (the customer property on Address); the other direction specifies a mapping to leverage.

Sample Model

 
import javax.persistence.*;
 
@Entity
public class Customer {
 
    @Id
    private long id;
 
    @OneToOne(mappedBy="customer", cascade={CascadeType.ALL})
    private Address address;
 
}
 
 
import javax.persistence.*;
 
@Entity
public class Address implements Serializable {
 
    @Id
    private long id;
 
    @MapsId
    @OneToOne
    @JoinColumn(name="ID")
    private Customer customer;
 
}

To marshal these objects to XML, mark one direction @XmlTransient' to prevent a JAXB infinite loop during marshalling. Normally, during unmarshalling (from XML-to-object), you are responsible for populating the back pointer

 
import javax.persistence.*;
import javax.xml.bind.annotation.*;
 
@Entity
public class Address implements Serializable {
 
    @Id
    private long id;
 
    @OneToOne
    @JoinColumn(name="ID")
    @MapsId
    @XmlTransient
    private Customer customer;
 
}

@XMLInverseReference

With the @XmlInverseReference annotation, MOXy will populate the back pointer automatically. In this sample, notice that the @XmlInverseReference annotation leverages the same "mappedBy" concept.

 
import javax.persistence.*;
import org.eclipse.persistence.oxm.annotations.*;
 
@Entity
public class Address implements Serializable {
 
    @Id
    private long id;
 
    @OneToOne
    @JoinColumn(name="ID")
    @MapsId
    @XmlInverseReference(mappedBy="address")
    private Customer customer;
 
}

Collections and Maps	Relationships	Advanced XML Schema Concepts
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