Possible drawbacks of Jettison Provider
19.7.2. Possible Problems with Jettison Provider If you have the resteasy-jackson-provider-xxx.jar in your classpath, the Jackson JSON provider will be triggered. This will screw up code that is dependent on the Jettison JAXB/JSon provider. If you had been using the Jettison JAXB/Json providers, you must either remove Jackson from your WEB-INF/lib or classpath, or use the @NoJackson annotation on your JAXB classes.