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. 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.