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From Daniel Kulp <dk...@apache.org>
Subject Re: CXF JAX-RS Provider for Aegis (Was: JAX-RS custom provider spring config)
Date Fri, 08 Feb 2008 15:23:33 GMT

One of the issues you may run into with Aegis is that it doesn't really 
create root elements at all as part of it's schema generation.   It 
really just generates types.   The frontend has to handle the global 
element creation stuff.     That's partially why there isn't a 
@AegisXMLRootElement thing.

Dan

On Friday 08 February 2008, Sergey Beryozkin wrote:
> Hi Jervis
>
> Great, it's good that you agree as well...
>
> I've started a new thread about what CXF JAX-RS can do to support
> alternative data binding providers, like Aegis.
>
> Can we just introduce some annotation which would serve purely as a
> marker and which our JAX-RS Aegis provider would recognize ? Something
> like @AegisXMLRootElement ?
>
> Cheers, Sergey
>
>
> ----- Original Message -----
> From: "Jervis Liu" <jervisliu@gmail.com>
> To: <cxf-dev@incubator.apache.org>
> Sent: Friday, February 08, 2008 12:06 PM
> Subject: Re: JAX-RS custom provider spring config
>
> > On Feb 8, 2008 7:46 PM, Sergey Beryozkin <sergey.beryozkin@iona.com> 
wrote:
> >> Hi Jervis
> >>
> >> This seems to be a bit complicated.
> >> I think that Barry's proposal is simple and effective.
> >>
> >> I doubt that we need to put some information or jars for all the
> >> default providers be picked up from some directory. That would be
> >> similar to the earlier proposal to provide them all in a spring
> >> configuration. Lets have defaut providers created as usual, on
> >> startup (or dynamically later on, based on a given consume/produce
> >> type) and be kept in one map.
> >>
> >> Lets have custom providers be picked up from either a spring
> >> configuration (Barry's patch) or from the classpath using a usual
> >> jar's ServiceProvider mechanism (same way as Jersey, this is
> >> something we can add later on) and kept them in a second map.
> >>
> >> Second map is checked first, first map with defaults is checked
> >> afterwards. It just works.
> >
> > Agreed. Yes, this should work and it is simpler.
> >
> >> About Aegis : it shoud have some sort of Aegis-specifoic
> >> annotations, shouldn't it ? This annotation can server as a hint to
> >> an Aegis provider, same was as @XMLRootElement serves as a hint to
> >> a JAXBProvider
> >
> > Aegis binding does not need any annotations on its type class.
> >
> >> Cheers, Sergey
> >>
> >>
> >>
> >>
> >>
> >> ----- Original Message -----
> >> From: "Jervis Liu" <jervisliu@gmail.com>
> >> To: <cxf-dev@incubator.apache.org>
> >>  Sent: Friday, February 08, 2008 11:34 AM
> >> Subject: Re: JAX-RS custom provider spring config
> >>
> >> > So based on what we have discussed so far, shall we agree on the
> >>
> >> followings?
> >>
> >> > 1. We do not need a programmatic API or Spring configuration to
> >>
> >> configure
> >>
> >> > Providers. Instead, we need to do three enhancements:
> >> >
> >> > a). Rather than hand-coded default (or pre-installed) providers
> >> > that
> >>
> >> need to
> >>
> >> > initialized when CXF JAX-RS starts up, we need to enhance CXF so
> >> > that
> >>
> >> CXF
> >>
> >> > can pick up all pre-installed providers from a dedicated
> >> > directory.
> >> >
> >> > b). CXF JAX-RS should scan a dedicated directory so that if a new
> >> > custom provider is installed or an old one is replaced in this
> >> > directory, it
> >>
> >> should
> >>
> >> > be able to load the provider without rebooting the runtime.
> >> >
> >> > c). The algorithm that decides which provider to use may need
> >> > some
> >>
> >> updates
> >>
> >> > as well.
> >> >
> >> >
> >> >
> >> > 2. We need the ability to specify an explicit provider to use
> >> > (probably using annotations on the resource class or on the
> >> > resource methods).
> >>
> >> This
> >>
> >> > feature is needed once we have more than one data binding
> >> > providers, i.e
> >>
> >> .,
> >>
> >> > JAXBProvider and  AegisProvider etc.
> >> >
> >> >
> >> >
> >> > Cheers,
> >> >
> >> > Jervis
> >> >
> >> > 2008/2/8 Liu, Jervis <jliu@iona.com>:
> >> >> There are a couple of issues that are covered or not covered yet
> >> >> by the spec. As Barry mentioned, the use case 1&2 are actually
> >> >> already covered
> >>
> >> by
> >>
> >> >> the spec. I.e, the JAX-RS runtime should maintain a list of
> >> >> default or pre-installed providers, for any custom providers
> >> >> installed by the
> >>
> >> users,
> >>
> >> >> they should be ordered before pre-installed providers. Please
> >> >> refer to
> >>
> >> the
> >>
> >> >> spec on the algorithm of how a provider is selected.
> >> >>
> >> >> One case which is not covered by the spec I believe, is the
> >> >> ability to explicitly specify a provider to use on the resource
> >> >> class or resource method. For example, lets say we have two data
> >> >> binding Providers, one
> >>
> >> is
> >>
> >> >> JAXBProvider, one is AegisProvider. In some cases, I may need to
> >> >> say explicitly that I want to use Aegis binding to
> >> >> marshal/unmarshal all my
> >>
> >> data
> >>
> >> >> types other than letting the jax-rs runtime to find the most
> >>
> >> appropriate
> >>
> >> >> provider for me.
> >> >>
> >> >> Cheers,
> >> >> Jervis
> >> >>
> >> >> > -----Original Message-----
> >> >> > From: Barry Fitzgerald [mailto:barfitzgerald@gmail.com]
> >> >> > Sent: 2008年2月8日 18:50
> >> >> > To: cxf-dev@incubator.apache.org
> >> >> >
> >> >>  > Subject: Re: JAX-RS custom provider spring config
> >> >> >
> >> >> > Hey Sergey,
> >> >> >
> >> >> > implementations when either could
> >> >> > handle the same request."
> >> >> >
> >> >> > I therefore think the best way to handle this is for the
> >>
> >> providerfactory
> >>
> >> >> to
> >> >>
> >> >> > maintain two lists of providers - user defined and default.
> >> >> >
> >> >> > When deciding how to handle a request it first checks the user
> >>
> >> defined
> >>
> >> >> to
> >> >>
> >> >> > see if any of these match. If no user defined providers match
> >> >> > it the
> >> >>
> >> >> falls
> >> >>
> >> >> > back to default list. I think this would handle both 1 & 2,
> >> >> > implement
> >> >>
> >> >> the
> >> >>
> >> >> > Spec correctly and would leave the spring syntax the same as
> >> >> > I've
> >> >>
> >> >> discussed.
> >> >>
> >> >> > Whatcha think?
> >> >> >
> >> >> > Barry
> >> >> >
> >> >> > On Feb 8, 2008 10:30 AM, Sergey Beryozkin
> >> >> > <sergey.beryozkin@iona.com>
> >> >> >
> >> >> > wrote:
> >> >> > > Hi there
> >> >> > >
> >> >> > > Few more comments.
> >> >> > >
> >> >> > > Jersey allows for external providers be picked up from a
> >> >> > > classpath
> >> >>
> >> >> using a
> >> >>
> >> >> > > ServiceProvider mechanism.
> >> >> > > If we compare that approach with using the spring
> >> >> > > configuration to
> >> >>
> >> >> inject
> >> >>
> >> >> > > entity providers, then we can see these are
> >> >> > > just two different paths for external providers to get into
> >> >> > > the
> >> >>
> >> >> runtime.
> >> >>
> >> >> > > In both cases there's really no need to specify all the
> >> >> > > entity
> >> >>
> >> >> providers
> >> >>
> >> >> > > (message body readers/writers as per the new api) which may
> >> >> > > be
> >>
> >> needed
> >>
> >> >> > for a
> >> >> >
> >> >> > > given application to function properly.
> >> >> > > As I said earlier, JAX-RS requires for a bunch of types like
> >>
> >> Response,
> >>
> >> >> > > JAXB-annotated ones, primitives, InputStream, Source, etc
be
> >>
> >> supported
> >>
> >> >> > out
> >> >> >
> >> >> > > of the box and after it gets finalized we'll have a TCK
> >> >> > > which will
> >> >>
> >> >> enforce
> >> >>
> >> >> > > that a given implementation does provide it all out of the
> >> >> > > box. Thus, a given user should only worry about external
> >> >> > > providers when
> >> >>
> >> >> none
> >> >>
> >> >> > of
> >> >> >
> >> >> > > the shipped providers can go the job. In this case,
> >> >> > > requiring a
> >>
> >> user
> >>
> >> >> to
> >> >>
> >> >> > > specify upfront a list of all the providers, including
> >> >> > > default ones
> >> >>
> >> >> (which
> >> >>
> >> >> > > can be nested or indeed private classes not intended for
the
> >> >>
> >> >> publication),
> >> >>
> >> >> > > would be problematic IMHO. Among other things, it would
> >> >> > > limit the
> >> >> >
> >> >> > dynamism
> >> >> >
> >> >> > > of a given application which can have new types/formats
> >> >> > > introduced
> >> >>
> >> >> after
> >> >>
> >> >> > it
> >> >> >
> >> >> > > has been started. I can also see users failing to specify
> >> >> > > the right
> >> >>
> >> >> list for
> >> >>
> >> >> > > a given application for the first few times and getting
> >> >> > > frustrated.
> >> >> > >
> >> >> > > As far as adding external entity providers is concerned,
I
> >> >> > > believe there're primarily two cases :
> >> >> > > 1. Runtime does not support the marshalling/unmarshalling
of
> >> >> > > a
> >>
> >> given
> >>
> >> >> > > custom type. In this case just specifying a custom
> >> >> > > provider's name
> >> >>
> >> >> would
> >> >>
> >> >> > do
> >> >> >
> >> >> > > (as in the Barry's proposed patch) and the instance would
be
> >> >> > > just
> >> >>
> >> >> added to
> >> >>
> >> >> > > the list of existing providers, the runtime will take care
> >> >> > > of
> >> >>
> >> >> utilizing it,
> >> >>
> >> >> > > based on its ProduceMime/ConsumeMime annotations and its
> >> >> > > support
> >>
> >> for
> >>
> >> >> > a given
> >> >> >
> >> >> > > class type.
> >> >> > > 2. Customer is not happy how, say, a given default provider
> >> >> > > works
> >> >>
> >> >> (that
> >> >>
> >> >> > > is, how, say, it's converted into/from text/plain
> >> >> > > representations)
> >>
> >> and
> >>
> >> >> would
> >> >>
> >> >> > > like to replace it with its own highly optimized
> >> >> > > implementation.
> >> >>
> >> >> JAX-RS
> >> >>
> >> >> > > requires such custom providers be supported. IMHO, this is
> >> >> > > not the
> >> >>
> >> >> highest
> >> >>
> >> >> > > priority issue for the CXF JAX-RS at this moment of time,
> >> >> > > but it's
> >> >>
> >> >> something
> >> >>
> >> >> > > which need to be supported. How we do it I'm not sure yet,
> >> >> > > we could introspect providers properly at the start.
> >> >> > >
> >> >> > > For example, lets say we have a default File provider (for
> >> >> > > all
> >>
> >> media
> >>
> >> >> types
> >> >>
> >> >> > > */*), as mandated by the spec, this provider just uses older
> >> >> > > plain
> >> >>
> >> >> File
> >> >>
> >> >> > > input/output streams wrapped into readers/writers. Customer
> >> >> > > wants
> >>
> >> to
> >>
> >> >> > replace
> >> >> >
> >> >> > > it with a nio-based implementation. At the start-up we can
> >> >> > > check
> >>
> >> the
> >>
> >> >> > > annotations for a given custom provider class and check if
> >> >> > > its
> >> >>
> >> >> instance
> >> >>
> >> >> > > supports any of the types already supported by the runtime
> >> >> > > and if
> >>
> >> yes
> >>
> >> >> then,
> >> >>
> >> >> > > for a given JAX-RS server endpoint, assume that a custom
> >> >> > > provider
> >> >>
> >> >> needs
> >> >>
> >> >> > to
> >> >> >
> >> >> > > take charge... or perhaps just replace the default instance
> >> >> > > which
> >>
> >> will
> >>
> >> >> have
> >> >>
> >> >> > > a global effect for al lthe endpoints. Something like that.
> >> >> > >
> >> >> > > Barry, have I convinced you :-) ? Would you be happy for
> >> >> > > your patch
> >>
> >> to
> >>
> >> >> > > address an issue 1 above for a start but such that no
> >> >> > > replacement
> >> >> >
> >> >> > happens ?
> >> >> >
> >> >> > > Thanks, Sergey
> >> >> > >
> >> >> > >
> >> >> > >
> >> >> > >
> >> >> > >
> >> >> > > Hi Barry
> >> >> > >
> >> >> > > Lets move a discussion on CXF-1425 to this list.
> >> >> > >
> >> >> > > In summary,
> >> >> > > we're discussing with Barry whether a list of JAX-RS Entity
> >>
> >> Providers
> >>
> >> >> > > (which know how to marshal/unmarshal given types) as
> >> >> > > configured in a given spring xml, should override a default
> >> >> > > list or
> >> >>
> >> >> not.
> >> >>
> >> >> > > IMHO it should not be the case. It would put a strain on
> >> >> > > users.
> >>
> >> Users
> >>
> >> >> do
> >> >>
> >> >> > > not need to know about the fact that a given Book class
> >> >> > > will only be marshalled if a JAXB-aware provider is
> >> >> > > installed. If a
> >> >>
> >> >> given
> >> >>
> >> >> > > set of returned types is large then it will get
> >> >> > > complicated. User just need to know about the content type,
> >> >> >
> >> >> > XMLRootElement
> >> >> >
> >> >> > > and similar things. Users do not need to know about class
> >> >> > > names for individual default providers, this will form some
> >> >> > > sort of
> >>
> >> a
> >>
> >> >> > > contract between a runtime and a user thus making it more
> >> >> > > difficult for us to change the things under the hood.
> >> >> > >
> >> >> > > For example, we can configure a Jetty handler, say we can
> >> >> > > add a
> >>
> >> Jetty
> >>
> >> >> > > handler. When doing it we do not need to specify all other
> >> >> > > types of handlers jetty may've set up under the hood. I
> >> >> > > believe we
> >> >>
> >> >> should
> >> >>
> >> >> > > follow the same practise in this case.
> >> >> > >
> >> >> > > As far as duplicates is conncerned : this is easy, lets just
> >> >> > > have a
> >> >>
> >> >> Set of
> >> >>
> >> >> > > full class names for individual providers. That would do
> >> >> > > for a start.
> >> >> > >
> >> >> > > Thoughts ?
> >> >> > >
> >> >> > > Cheers, Sergey
> >> >> > >
> >> >> > > ----------------------------
> >> >> > > IONA Technologies PLC (registered in Ireland)
> >> >> > > Registered Number: 171387
> >> >> > > Registered Address: The IONA Building, Shelbourne Road,
> >> >> > > Dublin 4,
> >> >>
> >> >> Ireland
> >> >>
> >> >> > > ----------------------------
> >> >> > > IONA Technologies PLC (registered in Ireland)
> >> >> > > Registered Number: 171387
> >> >> > > Registered Address: The IONA Building, Shelbourne Road,
> >> >> > > Dublin 4,
> >> >>
> >> >> Ireland
> >> >>
> >> >>
> >> >> ----------------------------
> >> >> IONA Technologies PLC (registered in Ireland)
> >> >> Registered Number: 171387
> >> >> Registered Address: The IONA Building, Shelbourne Road, Dublin
> >> >> 4,
> >>
> >> Ireland
> >>
> >>
> >>
> >> ----------------------------
> >> IONA Technologies PLC (registered in Ireland)
> >> Registered Number: 171387
> >> Registered Address: The IONA Building, Shelbourne Road, Dublin 4,
> >> Ireland
>
> ----------------------------
> IONA Technologies PLC (registered in Ireland)
> Registered Number: 171387
> Registered Address: The IONA Building, Shelbourne Road, Dublin 4,
> Ireland



-- 
J. Daniel Kulp
Principal Engineer, IONA
dkulp@apache.org
http://www.dankulp.com/blog

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