Re: [sca-j] ISSUE-179: Need type support for @Property when used with SDO

[Raymond Feng <rfeng@us.ibm.com>]

Hi,

Thanks for the clarification. 

To determine the XML type behind a Java
property, the following cases seem to be a natural order.

1) The property's Java type itself is
self-described to the underlying databinding technology, for example, a
generated static JAXB class or SDO class. 
2) The property is annotated in a databinding-specific
mechanism, for example, using JAXB annotations such as XmlSchemaType or
XmlJavaTypeAdapter. This can happen if the Java type is not a generated
JAXB class, such as Object or an interface.   
3) The property is annotated using SCA-defined
annotations. The proposal will provide a solution if both 1 and 2 are not
possible. (Some of the JAXB annotations are designed for similar purposes,
but I'm not sure we should force SCA developers to use JAXB annotations
for other databindings).
4) No XML type is provided, the java
type is mapped to xsd:anyType or not supported

Does this proposal only apply to properties
or do we want to generalize it for operation signatures (parameters and
return types)? If it is for properties only, I would prefer to enhance
@Property. Otherwise it makes sense to introduce something like @XMLType.

Thanks,
Raymond

---

Raymond Feng
Senior Software Engineer, Apache Tuscany PMC Member & Committer 
IBM Bay Area Lab, 1001 E Hillsdale Blvd, Suite 400,
Foster City, CA 94404, USA
E-mail: rfeng@us.ibm.com,
Notes: Raymond Feng/Burlingame/IBM, Tel: 650-645-8117,
T/L: 367-8117
Apache Tuscany: http://tuscany.apache.org

---

David Booz/Poughkeepsie/IBM@IBMUS wrote on 09/14/2009
11:56:23 AM:

> From:
> 
> David Booz/Poughkeepsie/IBM@IBMUS
> 
> To:
> 
> sca-j@lists.oasis-open.org
> 
> Date:
> 
> 09/14/2009 11:57 AM
> 
> Subject:
> 
> Re: [sca-j] ISSUE-179: Need type support for @Property when used with
SDO
> 
> Raymond, since you missed the telecon today, I thought I'd update
> you on potential compromise proposal that we discussed. Simon N will
> correct me if I get anything wrong as we invented this on the fly.
> 
> The current compromise proposal is to introduce a new SCA annotation
> (I'm proposing @XMLType below, but I don't really care about the 
> name) to capture the schema (or element) typing info instead of 
> capturing it on the property annotation itself.
> 
> So, an example might look like this:
> 
> package example;
> 
> import org.oasis.annotation.Property;
> import org.osoa.sca.annotations.Service;
> import commonj.sdo.DataObject;
> 
> @Service
> public class TypedComponentImpl {
> 
> private static final String TYPE_PREFIX = "{http://example}";
> private static final String ELEMENT_NAME = TYPE_PREFIX + "thing";
> private static final String TYPE_NAME = TYPE_PREFIX + "AThingType";
> 
> @Property
> @XMLType(type=TYPE_NAME)
> public DataObject dataObj1;
> 
> ...
> }
> 
> There are some advantages:
> 1) We could use it on parameters and return values. I need to 
> explore this further. It's not something we discussed today on the
call.
> 2) It is easy to say: "The @XMLType annotation MUST NOT be present
> when the @XmlJavaTypeAdapter annotation (or any other JAXB 
> annotation that assert a schema type) is present.". The @Property
> approach I had earlier suffers from the problem that we will have
to
> construct some complex rules in the spec to ensure that the 
> @Property annotation with the new attributes specified doesn't 
> collide with the presence of JAXB annotations. This new approach 
> (@XMLType) doesn't have that problem because we can simply disallow
both.
> 3) It's more modular - ok, this is a weak argument, because now an
> SDO programmer has to use two annotations and a JAXB guy probably
> only has to use one.
> 
> Thoughts? 
> 
> FWIW, I still prefer my original proposal, but I'm trying to keep
anopen mind.
> 
> 
> Dave Booz
> STSM, BPM and SCA Architecture
> Co-Chair OASIS SCA-Policy TC and SCA-J TC
> "Distributed objects first, then world hunger"
> Poughkeepsie, NY (845)-435-6093 or 8-295-6093
> e-mail:booz@us.ibm.com
> 
> [image removed] Raymond Feng---09/14/2009 01:21:13 PM---Hi, I have
a
> few comments/questions here.

> 
> [image removed] 
> From:
> 
> [image removed] 
> Raymond Feng/Burlingame/IBM
> 
> [image removed] 
> To:
> 
> [image removed] 
> Simon Nash <oasis@cjnash.com>
> 
> [image removed] 
> Cc:
> 
> [image removed] 
> David Booz/Poughkeepsie/IBM@IBMUS, sca-j@lists.oasis-open.org
> 
> [image removed] 
> Date:
> 
> [image removed] 
> 09/14/2009 01:21 PM
> 
> [image removed] 
> Subject:
> 
> [image removed] 
> Re: [sca-j] ISSUE-179: Need type support for @Property when used with
SDO
> 
> 
> 
> Hi,
> 
> I have a few comments/questions here.
> 
> 1) JAXB is part of JDK since version 1.6. Does sca-j spec mandate
JDK 6?
> 
> 2) It seems to me that you propose to use JAXB as the canonical 
> databinding. If SDO or other databindings (such as DOM) is used, 
> then the application developer is responsible for mapping it to 
> JAXB. If an application developer is required to generate JAXB 
> classes, why SDO is chosen in the first place? 
> 
> 3) I like Dave's original proposal better as it allows us to 
> configure/customize the Java types with XML information in a 
> databinding-agnostic way, when such metadata cannot be acquired by
> introspection. The SCA runtime can then use that in the databinding-
> specific typing system (such as JAXBContext or SDO HelperContext).
> 
> Initially I also thought of adopting JAXB annotations such as 
> XmlSchemaType, XmlAttribute, XmlElement, XmlAnyElement, 
> XmlAnyAttribute to supply the XSD type/element/attribute for java
> types. But it seemed to be a bit strange that we use one databinding
> (JAXB) to describe another databinding.
> 
> Thanks,
> Raymond
> Raymond Feng
> Senior Software Engineer, Apache Tuscany PMC Member & Committer
> IBM Bay Area Lab, 1001 E Hillsdale Blvd, Suite 400, Foster City, CA
94404, USA
> E-mail: rfeng@us.ibm.com, Notes: Raymond Feng/Burlingame/IBM, Tel:
> 650-645-8117, T/L: 367-8117
> Apache Tuscany: http://tuscany.apache.org
> 
> 
> Simon Nash <oasis@cjnash.com> wrote on 09/14/2009 07:30:34 AM:
> 
> > From:
> > 
> > Simon Nash <oasis@cjnash.com>
> > 
> > To:
> > 
> > David Booz/Poughkeepsie/IBM@IBMUS
> > 
> > Cc:
> > 
> > sca-j@lists.oasis-open.org
> > 
> > Date:
> > 
> > 09/14/2009 07:31 AM
> > 
> > Subject:
> > 
> > Re: [sca-j] ISSUE-179: Need type support for @Property when used
with SDO
> > 
> > Dave,
> > Responses inline below.
> > 
> >    Simon
> > 
> > David Booz wrote:
> > > Hi Simon,
> > > 
> > > Thanks for the research. Don't you think it would be quite
odd if the 
> > > spec required the use of JAXB emitters (this is what I find
the most 
> > > troubling) in order to use SDO with a specific schema type?
> >  >
> > JAXB is built built into the JDK, so I'm not sure why it is burdensone
> > to run the JAXB emitters.  The emitted class could be placed
in a
> > separate Java package that clearly identifies it as an emitted
> > JAXB artifact and doesn't interfere with any classes in Java
packages
> > used by the implementation.
> > 
> > >                
                     
                     
My argument 
> > > remains the same. We need a way to simplify the use of SDO
as a 
> > > databinding technology, enabling the developers to work
with the minimal 
> > > number of building blocks. While I agree that the @XmlJavaTypeAdapter
> > > seems to "work", it doesn't meet the requirement
as something that would 
> > > be intuitive to use because it introduces extra concepts
that the 
> > > developer doesn't really need. The simple extension that
I've proposed 
> > > provides an easily understandable integration point because
the 
> > > developer only has to deal with the SDO API and XML schema.
> > > 
> > Support for @XmlJavaTypeAdapter is already mandated in SCA-J,
and JAXB
> > is a standard part of the JDK.  It seems very strange to
me to invent
> > a new facility that duplicates existing capabilities that are
included
> > in SCA-J and the JDK.  IMO this is more confusing for developers
than
> > explaining how they can use existing capabilities to do what
they need.
> > 
> > > The @XmlAnyElement seems like a reasonable approach for
the mapping of 
> > > SDO to <any/>, so I can probably live with it for
those use cases that 
> > > require <any/>. Are there any other JAXB annotations
that would have to 
> > > appear in the Java class in order to make this work?
> > > 
> > No other annotations are needed.
> > 
> >    Simon
> > 
> > > Dave Booz
> > > STSM, BPM and SCA Architecture
> > > Co-Chair OASIS SCA-Policy TC and SCA-J TC
> > > "Distributed objects first, then world hunger"
> > > Poughkeepsie, NY (845)-435-6093 or 8-295-6093
> > > e-mail:booz@us.ibm.com
> > > 
> > > Inactive hide details for Simon Nash ---09/05/2009 07:46:03
AM---On 
> > > Friday's call I took an action to see whether JAXB annotatiSimon
Nash 
> > > ---09/05/2009 07:46:03 AM---On Friday's call I took an action
to see 
> > > whether JAXB annotations can be used to override the defaul
> > > 
> > > 
> > > From:   
> > > Simon Nash <oasis@cjnash.com>
> > > 
> > > To:   
> > > sca-j@lists.oasis-open.org
> > > 
> > > Date:   
> > > 09/05/2009 07:46 AM
> > > 
> > > Subject:   
> > > Re: [sca-j] ISSUE-179: Need type support for @Property when
used with SDO
> > > 
> > > ------------------------------------------------------------------------
> > > 
> > > 
> > > 
> > > On Friday's call I took an action to see whether JAXB annotations
can be
> > > used to override the default JAXB mapping from a Java property
type
> > > to a schema type.
> > > 
> > > The answer is that this can be done with the @XmlJavaTypeAdapter
> annotation.
> > > If there is a property whose Java type is the interface
DataObject and it
> > > needs to be mapped to a specific schema type such as "address",
the 
> > > following
> > > steps are needed:
> > >  1. Create an xsd file for the "address"
schema type.
> > >  2. Generate a Java class Address from this xsd file
using JAXB.
> > >  3. Create a JAXB adapter class to specify the property
mapping, for 
> > > example:
> > >      public class AddressAdapter extends
XmlAdapter<Address, DataObject> {
> > >        public DataObject unmarshal(Address
value) {
> > >          // If the SCA runtime
will use the JAXB unmarshaller to convert
> > >          // the property value
to a Java object, this method needs to
> > >          // contain code to create
an instance of DataObject 
> from an Address
> > >          // object passed in by
the JAXB unmarshaller. If the property
> > >          // conversion will be
done in some other way (e.g., by SDO), this
> > >          // method can just return
null.
> > >        }
> > >        public Address marshal(DataObject
value) {
> > >          return null; // SCA properties
are never converted from
> Java to XML
> > >        }
> > >      }
> > >  4. Annotate the property whose Java type is DataObject
with the
> > >     annotation @XmlJavaTypeAdapter(AddressAdapter.class)
> > > A separate adapter class is required for every schema type
that is a 
> > > possible
> > > mapping target for the property.
> > > 
> > > If the property needs to be mapped to a specific schema
element instead of
> > > a schema type, the steps are the same except that an "address"
schema 
> > > element
> > > is used in step 1, and an additional annotation @XmlElement
> (name="address")
> > > is used on the property in step 4.
> > > 
> > > If the property needs to be mapped to a schema <any>
element, 
> steps 1, 2 and
> > > 3 are not needed.  In step 4, the annotation @XmlAnyElement
is used on the
> > > property instead of @XmlJavaTypeAdapter.
> > > 
> > > I have verified all of the above with some simple test code.
> > > 
> > >   Simon
> > > 
> > > David Booz wrote:
> > >  > http://www.osoa.org/jira/browse/JAVA-179
> > >  >
> > >  > Dave Booz
> > >  > STSM, BPM and SCA Architecture
> > >  > Co-Chair OASIS SCA-Policy TC and SCA-J TC
> > >  > "Distributed objects first, then world hunger"
> > >  > Poughkeepsie, NY (845)-435-6093 or 8-295-6093
> > >  > e-mail:booz@us.ibm.com
> > >  >
> > >  > Inactive hide details for David Booz---08/24/2009
04:16:58 PM---TARGET:
> > >  > Java CAA CD03 and Java POJO CD01 DESCRIPTION:David
Booz---08/24/2009
> > >  > 04:16:58 PM---TARGET: Java CAA CD03 and Java
POJO CD01 DESCRIPTION:
> > >  >
> > >  >
> > >  > From:
> > >  > David Booz/Poughkeepsie/IBM@IBMUS
> > >  >
> > >  > To:
> > >  > sca-j@lists.oasis-open.org
> > >  >
> > >  > Date:
> > >  > 08/24/2009 04:16 PM
> > >  >
> > >  > Subject:
> > >  > [sca-j] NEW ISSUE: Need type support for @Property
when used with SDO
> > >  >
> > >  > 
> ------------------------------------------------------------------------
> > >  >
> > >  >
> > >  >
> > >  > TARGET: Java CAA CD03 and Java POJO CD01
> > >  >
> > >  > DESCRIPTION:
> > >  > SDO DataObject can be mapped to any XML schema
type, and therefore
> > >  > literally <any> as well. There is no way
to specify the concrete XML
> > >  > type of a Java property who's Java type is SDO
DataObject.
> > >  >
> > >  > PROPOSAL:
> > >  > Will be attached to JIRA once the issue is logged.
> > >  > Basically, the proposal will introduce two new
attributes on @Property,
> > >  > xmlType (for specifying the XML schema type)
and xmlElement (for
> > >  > specifying an XML global element that denotes
the type). The new
> > >  > attributes are mutually exclusive.
> > >  >
> > >  >
> > >  > Dave Booz
> > >  > STSM, BPM and SCA Architecture
> > >  > Co-Chair OASIS SCA-Policy TC and SCA-J TC
> > >  > "Distributed objects first, then world hunger"
> > >  > Poughkeepsie, NY (845)-435-6093 or 8-295-6093
> > >  > e-mail:booz@us.ibm.com
> > >  >
> > > 
> > > 
> > > ---------------------------------------------------------------------
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> > > 
> > > 
> > > 
> > 
> > 
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