Is it possible to set ETags using JAX-RS without resorting to Response objects?

Question

In one of the few questions (with answers) I have found on SO regarding JAX-RS and caching, the answer to generating ETags (for caching) is by setting some values on the Respons

Answer 1

or it can be as simple as sending back an "error" code... depending on what you want to do.

@Path("/{id}")
@GET
@Produces({MediaType.APPLICATION_JSON, MediaType.APPLICATION_XML})
public ProductSearchResultBean getProductById(@PathParam("id") Integer productId, @QueryParam("expand") List expand, @Context HttpServletRequest request, @Context HttpServletResponse response) throws IOException {

    ProductSearchResultBean productDetail = loadProductDetail(productId, expand);

    EntityTag etag = new EntityTag(((Integer)(productDetail.toString().hashCode())).toString());
    String otherEtag = request.getHeader("ETag");
    if(etag.getValue().equals(otherEtag)){
        response.sendError(304, "not Modified");
    }

    response.addHeader("ETag", etag.getValue());

    return productDetail;
}

That's how I tackled the issure anyway. Good luck! (Use Spring MVC instead.... there's an out of the box filter that does EVERYTHING for you... even making a good ETag :) )