How to force JAXB marshaller to use xlink references?

Question

I use JAXB marshaller to store some java objects as XML files. Some of these objects reference each other, so I unsurprisingly obtain this error:

[com.sun.istack.internal.SAXException2: A cycle is detected in the object graph. This will cause infinitely deep XML

The solution which consists in removing the cycles and use only tree structure is not feasible - I need both navigability directions.

To solve this issue, I would rather use xlink to reference the xml objects instead of copying them in cascade. Is this solution pertinent? Is it possible to do that with JAXB marshaller? How?

Answer 1

You can implement an XLink approach in JAXB using an XmlAdapter. Below are links to various similar answers.

• Serialize a JAXB object via its ID?
• Using JAXB to cross reference XmlIDs from two XML files
• Can JAXB marshal by containment at first then marshal by @XmlIDREF for subsequent references?

I lead the EclipseLink JAXB (MOXy) implementation, and we have the @XmlInverseReference extension for mapping bidirectional relationship that you may be interested in:

• http://blog.bdoughan.com/2010/07/jpa-entities-to-xml-bidirectional.html

Answer 2

Dude, you can note in one of the entity the annotation @XmlTransient, so when unmarch, it will not complain about the cycle problem.

But with thius workaround after unmarch the xml you will have to populate the atribute with the @XmlTransient.

I was reading some paper and find this. You can set @XmlTransient and use the callback method to do something after the unmarch. So you can set the parent to you child.

public void afterUnmarshal(Unmarshaller u, Object parent) {
    this.pessoa = (Pessoa) parent; }