I have an object graph that contains a cycle. How do I get JAXB to handle this? I tried using the @XmlTransient
annotation in the child class but the JAXB mar
We can use XStream library as well, I tried it one project where JAXB was giving cyclic error but XStream handled it successfully
The good thing about using JAXB is that it is a standard runtime with multiple implementations (just like JPA).
If you use EclipseLink JAXB (MOXy) then you have many extensions available to you for handling JPA entities including bi-directional relationships. This is done using the MOXy @XmlInverseReference annotation. It acts similar to @XmlTransient on the marshal and populates the target-to-source relationship on the unmarshal.
http://wiki.eclipse.org/EclipseLink/Examples/MOXy/JPA/Relationships
@Entity
@XmlRootElement
public class Contact {
@Id
private Long contactId;
@OneToMany(mappedBy = "contact")
private List<ContactAddress> addresses;
...
}
@Entity
@XmlRootElement
public class ContactAddress {
@Id
private Long contactAddressId;
@ManyToOne
@JoinColumn(name = "contact_id")
@XmlInverseReference(mappedBy="addresses")
private Contact contact;
private String address;
...
}
Other extensions are available including support for composite keys & embedded key classes.
To specify the EcliseLink MOXy JAXB implementation you need to include a jaxb.properties file in with your model classes (i.e. Contract) with the following entry:
javax.xml.bind.context.factory=org.eclipse.persistence.jaxb.JAXBContextFactory
XMLTransient almost always works for cycles. It might be a possibility that you have XMLTransient on the field level but you have not specified XMLAccessorType to be XmlAccessType.Field. If you don't specify anything the default is XmlAccessType.Property - or your getters. I have experienced Jaxb picking xml elements from getters from a class that I missed the accessor type annotations on and still work perfectly fine.
This page in the "Unofficial JAXB Guide" offers three strategies for dealing with cycles. They are (in summary):
just look at this tutorial : Mapping cyclic references to XML by jaxb
I use it an it works well :)