I recently had to migrate to a new machine and re-installed Eclipse. At the moment, I need to generate JAXB classes from an xsd. I cannot quite remember what I installed, b
(I'm using IBM's Eclipse-based RAD, so I don't know whether this applies to raw Eclipse.)
Have a look at your project Facets (select project, rightClick->Properties, Project Facets) I have the option of selecting JAX/RS.
later: I've checked my plugins and by default I get Dali installed and it does contain some JAX/B-related stuff. I suspect you do need this.