Is it possible to set ETags using JAX-RS without resorting to Response objects?
caching, cxf, etag, java, jax-rs
Solution
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<Message> {
public MyInterceptor () {
super(Phase.MARSHAL);
}
public final void handleMessage(Message message) {
MultivaluedMap<String, Object> headers = (MetadataMap<String, Object>) message.get(Message.PROTOCOL_HEADERS);
if (headers == null) {
headers = new MetadataMap<String, Object>();
}
//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();
Problem
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 Response object. As in the following: ``` @GET @Path("/person/{id}") public Response getPerson(@PathParam("id") String name, @Context Request request){ Person person = _dao.getPerson(name); if (person == null) { return Response.noContent().build(); } EntityTag eTag = new EntityTag(person.getUUID() + "-" + person.getVersion()); CacheControl cc = new CacheControl(); cc.setMaxAge(600); ResponseBuilder builder = request.evaluatePreconditions(person.getUpdated(), eTag); if (builder == null) { builder = Response.ok(person); } return builder.cacheControl(cc).lastModified(person.getUpdated()).build(); } ``` The problem is that will not work for us, since we use the same methods for both SOAP and REST services, by annotating the methods with @WebMethod (SOAP), @GET (and whatever else we might need to expose the service). The previous service would look like this to us (excluding the creation of headers): ``` @WebMethod @GET @Path("/person/{id}") public Person getPerson(@WebParam(name="id") @PathParam("id") String name){ return _dao.getPerson(name); } ``` Is there any way - through some extra configuration - of setting those headers? This is the first time I have found that using Response objects actually has some benefit over just auto-conversion ... We are using Apache CXF.