JSON Support via Java EE 7 JSON-P API
No, this is not the JSONP you are thinking of! JSON-P is a new Java EE 7 JSON parsing API. Horrible name for a new JSON parsing API! What were they thinking? Anyways, Resteasy has a provider for it. If you are using Wildfly, it is required by Java EE 7 so you will have it automatically bundled. Otherwise, use this maven dependency.
<dependency>
<groupId>org.jboss.resteasy</groupId>
<artifactId>resteasy-json-p-provider</artifactId>
<version>3.1.0-SNAPSHOT</version>
</dependency>
It has built in support for JsonObject, JsonArray, and JsonStructure as request or response entities. It should not conflict with Jackson or Jettison if you have that in your path too.