https://jsr311.dev.java.net/nonav/javadoc/javax/ws/rs/ext/MessageBodyWriter.html#writeTo(T,%20java.lang.Class,%20java.lang.reflect.Type,%20java.lang.annotation.Annotation[],%20javax.ws.rs.core.MediaType,%20javax.ws.rs.core.MultivaluedMap,%20java.io.OutputStream)
type - the class of object that is to be written.
So I don't think we should pass Object.class for MessageBodyWriter<Object>. If one would like to avoud doing casts during testing
then it should be just MessageBodyWriter<Book> and I'm pretty sure the runtime will pass Book.class.
Cheers, Sergey
On Sat, Sep 5, 2009 at 1:57 PM, Benson Margulies <bimargul...@gmail.com>wrote:
JAX-RS defines two fundamental interfaces: MessageBodyReader<T> and
MessageBodyWriter<T>, and providers implement.
I claim that GENERIC providers that work for any object (like those
corresponding to data bindings) should, themselves, be GENERIC, and
implement MessageBodyX<T>, not MessageBodyX<Object>.
Allow me to modulate this claim. I thought about it some more.
If you want to define a class as 'implements MessageBodyX<Object>', fine.
However, the right thing to pass to the Class<T> argument will ALWAYS be
Object.class. If you want to cue in the code to the sort of object in
flight, use the Type argument further down the parameter list.
I claim this because the whole API structure of MessageBodyX assumed this.
It uses Class<T> in a way that requires constant
@SupressWarnings("unchecked") if the base is MessageBodyX<Object>.
To put my money where my mouth is, as it were, I implemented this for the
Aegis providers. When I did this, I discovered that the JAX-RS runtime code
couldn't handle generic type providers. When the provider type is, say,
AegisElementProvider<Book>
then implemented interface comes up as MessageBodyReader<T>, not
MessageBodyReader<Book>. So it is a TypeVariable, not a class or a
ParameterizedType.
I fixed the provider selection code to cope, but I didn't write the
additionally complex code to look at bounds and insist that if there is a
bound the type at hand be within it.
