Factory methods in JAXB accessing the element?

Question

I am trying to use a factory method instead of a no-args constructor for JAXB.

I have multiple classes that inherit from a base class, and the only indication as to which would be instantiated is an attribute type in the xml element.

<tag-name type="boolean"/>

would instantiate a BooleanType, whereas

<tag-name type="integer"/>

would instantiate an IntegerType.

Is there any way I can access the element name / attribute values of the element being unmarshalled from within the factory method?

(Is this, perhaps, a benefit of using a factory method over a no-args constructor? Are there others?)

(I am not using MOXy)

Answer 1

I have multiple classes that inherit from a base class, and the only indication as to which would be instantiated is an attribute type in the xml element.

Using any JAXB (JSR-222) implementation you could use an XmlAdapter to map an inheritance relationship where an arbitrary XML attribute is the inheritance indicator.

• http://blog.bdoughan.com/2012/01/jaxb-and-inhertiance-using-xmladapter.html

However instead of using an arbitrary XML attribute I would use the xsi:type attribute so that the contents could be properly validated by an XML schema.

• http://blog.bdoughan.com/2010/11/jaxb-and-inheritance-using-xsitype.html

If you still wanted to use an arbitrary XML attribute and you were using EclipseLink MOXy are your JAXB provider then you could leverage the @XmlDescriminatorNode / @XmlDescriminatorValue extension:

• http://blog.bdoughan.com/2010/11/jaxb-and-inheritance-moxy-extension.html

---

Is there any way I can access the element name / attribute values of the element being unmarshalled from within the factory method?

JAXB implementations do allow you to specify factory classes and methods via the @XmlType annotation, but I do not believe this is what you are looking for in this use case.

• http://blog.bdoughan.com/2011/06/jaxb-and-factory-methods.html

To leverage the XML contents to determine the appropriate subclass to instantiate you would need to use the XmlAdapter approach.