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

Yes you might be able to use interceptors to achieve this if you could generate the E-tag AFTER you create your response object.

public class MyInterceptor extends AbstractPhaseInterceptor {

    public MyInterceptor () {
        super(Phase.MARSHAL);
    }

    public final void handleMessage(Message message) {
        MultivaluedMap headers = (MetadataMap) message.get(Message.PROTOCOL_HEADERS);

        if (headers == null) {
            headers = new MetadataMap();
        }             

        //generate E-tag here
        String etag = getEtag();
        // 
        String cc = 600;

        headers.add("E-Tag", etag);
        headers.add("Cache-Control", cc);
        message.put(Message.PROTOCOL_HEADERS, headers);
    }
}

If that way isn't viable, I would use the original solution that you posted, and just add your Person entity to the builder:

Person p = _dao.getPerson(name);
return builder.entity(p).cacheControl(cc).lastModified(person.getUpdated()).build();