How to dynamically add xml element to a java JAXRS representation?

Question

Say I have a java class that is a representation of a "Dog" with attrbutes "Color" and "Type" marked up with @XmlElement and @XmlRootElement tags. How do I add a "Age" xml element to this JAXRS based class programmatically without modifying my Dog class with @XmlAttribute(name="Age") ?

Assume I have the representation:

DogRepClass adog = new DogRepClass();

Answer 1

You'd have to create your own MessageBodyWriter but rather than make your own from scratch, you can extend it to process some custom annotations that your message body writer can recognize via the .entity(Object, Annotation[]) method. That way you just add on something specific for your needs

Answer 2

You can define your own MessageBodyWriter (http://jsr311.java.net/nonav/javadoc/javax/ws/rs/ext/MessageBodyWriter.html) only for this particular type. It can marshall your instance into DOM, modify it and serialize afterwards. Not nice nor elegant, but it will work.