Hi Benson
----- Original Message -----
From: "Benson Margulies" <bimargul...@gmail.com>
To: "CXF Dev" <dev@cxf.apache.org>
Sent: Monday, August 31, 2009 6:33 PM
Subject: generics and type mapping in Aegis
Sergey's issues with JAX-RS have started me looking at how Aegis maps types.
The following temptation now occurs: allow the fundamental aegis type
mechanism to map generics. Somene could thus add a mapping from any X<y,x,q>
-> XML via a custom type. Of course, with type erasure, this only will pay
attention to the declared type, not the dynamic type.
Somehow, I feel as if this is a slippery slope we don't want to start down.
However, the defined APIs for JAX-RS have started us there, with their extra
arguments for generic type specs. Apparently, someone thinks that it's so
important to be able to write a Collection<X> to the top of JAX-RS to
justify adding an asymmetry.
Have a look at this JAXRS resource class :
http://svn.apache.org/repos/asf/cxf/trunk/rt/frontend/jaxrs/src/test/java/org/apache/cxf/jaxrs/fortest/BookEntity.java
and this one :
http://svn.apache.org/repos/asf/cxf/trunk/rt/frontend/jaxrs/src/test/java/org/apache/cxf/jaxrs/fortest/AbstractEntity.java
At runtime the parameter type of BookEntity.postEntity(new Book()) is Object
but its Type is TypeVariable that leads to Book.class.
CXF takes care of hiding these details from JAXRS providers but I'm not sure it is the case with all other JAXRS impls so one can
imagine custom writers actually needing to deal with Type params...And if it were the case then it would make life more complicated
for users - thus having seperate parameters lets some implemetations to avoid it.
Perhaps there've been some other or just completely different motivations behind introducing Class and Type - for ex,
MessageBodyWriter/Reader interfaces are parameterized so say
CustomBodyWriter implements MessageBodyWriter<Foo>
would lead to Class<Foo> being generated in some method signatures, thus allowing the runtimes to do some additional checks, with
Types alone it would not be possible
cheers, Sergey
Anybody else got a thought here?
