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I would like to start the disucssion on AXIS2 integration for Tuscany. 
 
I started to prototype the AXIS2 support for Tuscany web service binding. 
Following the similar approach as we do for Axis 1.x, the key enabling factor 
is the serialization/deserialization from SDO to AXIOM and vice versa. 
Generally speaking, it's all about the transformations between different XML 
bindings for the same data. Please see the attached the diagram for some 
examples. attachment:XMLDataBinding
 
As the default data model for Tuscany, SDO DataObject is used to represent the 
input/output/fault message for web services. (Later on, it could be pluggable.)
 
In Axis 1.x, the SOAP envelope is a DOM-based model. 
 
Serialization: SDO --> DOM (SOAP) 
Deserialization: DOM --> SDO
 
Due to some issues of the DOM support in the SDO 1.0 implementation, we made 
some workarounds in the current code base. So the real path may look like this:
 
Serialization: SDO --> String --> SOAP
Deserialization: SOAP --> String --> SAX --> SDO
 
In Axis 2, SOAP messages are modeled using AXIOM (AXis Object Model) which is 
an XML object model working on StAX (Streaming API for XML) parsing optimized 
for SOAP 1.1/1.2 Messages. The ideal path should be:
 
Serialization: SDO --> StAX --> SOAP (AXIOM)
Deserialization: SOAP (AXIOM) --> StAX --> SDO
 
The StAX support is not there yet in the current SDO implementation. So I took 
a hacky way and managed to make this path work with the Axis2 0.93 driver for 
the outbound Web Service call.
 
Serialization: SDO --> AXIOM (by the special XMLSaveImpl which creates AXIOM 
attributes/elements/text in a similar way as DOM)
Deserialization: AXIOM --> StAX --> StAX2SAXAdapter --> SAX --> SDO
 
Now it becomes desirable to have a set of flexible SDO2 
serializer/deserializers (or XMLResource in the SDO/EMF term) as follows:
 
SAX: Generate SAX events from DataObject and load DataObject from SAX events
Stax: Implement StAX XMLStreamReader for a given DataObject and load DataObject 
from XMLStreamReader (potentially can support lazy-loading of DataObject?)
DOM: Create DOM tree from DataObject and load DataObject from DOM
 
IMHO, these utilities will not only benifit the SDO/Axis integration, but also 
the transformation between SDO and other models like JAXB and XMLBeans.
 
Ideas? Opinions?
 
Thanks,
Raymond
 

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