I want my REST service's GET requests to be cached by a forward caching service.
By default, my Restlet responses are not getting cached. The service we use
says:
"Our system does not support Vary headers with any value other than
Accept-Encoding. This is because this setting would imply that the
content could be different although the URL itself remains constant."
I'm not familiar with the details of content negotiation (I'd love to be
enlightened if anyone can post a summary), but I gather (a) it's a common
RESTful practice, and (b) I don't have much use for it since my Resources are
only represented as XML with the same language and character set.
By default my Restlet response headers have "Vary:
Accept-Charset,Accept-Encoding,Accept-Language,Accept". To be cachable by our
service, I have to remove most of those. It looks like those 'Dimensions' are
being added by Resource.handleGet(), and there's no way to override what gets
added. I have custom Resource implementations that all extend the same parent
class, so in that parent I've overridden handleGet() as follows:
public void handleGet() {
super.handleGet();
Set<Dimension> dims = getResponse().getDimensions();
dims.remove(Dimension.CHARACTER_SET);
dims.remove(Dimension.LANGUAGE);
dims.remove(Dimension.MEDIA_TYPE);
}
Is this okay? It seems to work fine, but I wasn't sure if there was ever a
point-of-no-return regarding Responses, e.g. if bytes have already been streamed
back and headers can no longer be changed.
I'm posting all this:
(1) To start a discussion that may benefit others who may run into this
problem with HTTP caching services,
(2) To find out what features I'm missing by removing these Dimensions,
(3) In case my plight influences Jerome and Thierry (who are great at
responding to user feedback, btw) to add something like "protected void
setGetResponseDimentions()", if it's warranted... or in some way to override the
Resources behavior without doing my
call-the-super-method-and-then-undo-part-of-what-it-did override.
Stokes.
