On Nov 2, 2007, at 9:55 AM, Ryan J. McDonough wrote:
> As I read through some the spec and some of the Jersey code, I am
> not clear on how the proper syntax on how to create a custom
> EntityProvider. To help clarify my understanding, I have some code
> below for a theoretical ImageEntityProvider which would be able to
> render an Image representation. Based on what I have read so far,
> this is my understanding so far on how to implement it:
>
> @Provider
> public class ImageEntityProvider implements EntityProvider<IIOImage> {
> @ConsumeMime("application/xml,image/jpg,image/png,image/gif")
> public IIOImage readFrom(Class<IIOImage> type,
> MediaType mediaType,
> MultivaluedMap<String, String> httpHeaders,
> InputStream entityStream)
> throws IOException {...}
> @ProduceMime("image/jpg,image/png,image/gif")
> public void writeTo(IIOImage image,
> MediaType mediaTypes,
> MultivaluedMap<String, Object> httpHeaders,
> OutputStream entityStream)
> throws IOException {...}
>
Move the ConsumeMime and ProduceMime to the class as you show below,
you also need to add the supports method. The supports method allows
an entity provider to support entities based on criteria other than
the class of the entity. E.g. the JAXB provider is declared as
"implements EntityProvider<Object>" but only supports classes
annotated with @XmlRootElement.
> The spec also mentions the use of the @Contract annotation, but I'm
> not clear on the proper usage or the specific functionality it
> provides. In regards to the @ProduceMime and @ConsumeMime
> annotations, is it also possible to be able to annotate the
> provider this way?
>
> @Provider
> @ProduceMime("image/jpg,image/png,image/gif")
> @ConsumeMime("application/xml,image/jpg,image/png,image/gif")
> public class ImageEntityProvider implements EntityProvider<IIOImage> {
>
> public IIOImage readFrom(Class<IIOImage> type,
> MediaType mediaType,
> MultivaluedMap<String, String> httpHeaders,
> InputStream entityStream)
> throws IOException {...}
>
> public void writeTo(IIOImage image,
> MediaType mediaTypes,
> MultivaluedMap<String, Object> httpHeaders,
> OutputStream entityStream)
> throws IOException {...}
>
>
> I'm just trying to clarify how this all should work in practice as
> it seems a bit vague at the moment. Is this syntax correct?
>
Exactly. Support for @Provider isn't yet implemented in Jersey which
instead uses files in jersey/src/impl/META-INF/services to discover
providers. The plan is that the JSR 311 runtime will scan for classes
annotated with @Contract and @Provider to remove the need for such
static configuration files. @Contract identifies an interface/
abstract class for which providers are expected (e.g.
EntityProvider), this corresponds to the name of the files currently
in jersey/src/impl/META-INF/services. @Provider identifies classes
that implement one or more interfaces/abstract classes annotated with
@Contract and this corresponds to an entry in one of the files in
jersey/src/impl/META-INF/services.
Hope that makes it a little clearer.
Marc.
---
Marc Hadley <marc.hadley at sun.com>
CTO Office, Sun Microsystems.