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From "Eran Chinthaka" <chinth...@opensource.lk>
Subject RE: [Axis2] Proposal - DOM Implementation for Axis2
Date Tue, 17 May 2005 05:10:42 GMT


> 
> hi,
> 
> doesn't it mean that XML will be parsed twice or events replayed
> (PullParser pp = messageContext.getSOAPEnvelope().getPullParser())  and
> original OM tree that was first built is then discarded (first built by
> StAXSOAPModelBuilder but without DOM then again by StAXSOAPModelBuilder
> but with DOM)?
> 
> i think there is a better solution: if it is detected that that one of
> modules/handlers requires DOM (described in its metadtaa) then why not
> to use builder/factory that will produce OM classes that implement DOM
> interfaces from beginning?

Yeah, this is the nice picture we like to see, which may not be the actual
picture.

We create the builder within the transport. So do u want to expect the
transport to find the correct builder and assign ?  

And take this example. We know that there is a service in our Axis Server,
which security is optional. Meaning messages may come with or without
encrypted. So when a message comes to the service how can the transport
know, whether the message is encrypted or not. If he knows that, yes we have
the nice cute picture u mentioned ;).

So that's the reason behind us treating the message as a usual one
initially, and if the domain specific handler, like wsse handler, detects
what to do he can follow the proposal put forward by Ruchith.

Regards,
Chinthaka


> 
> alek
> 
> 
> Ruchith Fernando wrote:
> 
> >Hi All,
> >
> >In implementing WS-Security capabilities on Axis 2.0 we will have to
> >convert the OM to DOM and provide the complete SOAPEnvelope as a DOM
> >implementation.
> >The following changes and additions are proposed to the OM
> >implementation to support this.
> >
> >1.) The org.w3c.dom.* interfaces will be implemented extending the OM
> >Impls. (org.apache.axis.dom.*)
> >Also there will be an implementation of org.apache.axis.soap.*
> >interfaces extending from the DOMImpls. (org.apache.axis.dom.soap.*)
> >In this situation we will have to change some of the method names in
> >the OM interfaces. E.g.: getNextSibling, getPreviousSibling in OMNode
> >
> >2.) A DOMSOAPFactory implementing the SOAPFactory will be introduced
> >to provide the DOM_SOAP impls. to the StAXSOAPModelBuilder
> >
> >3.) How to switch the builder when the security related handlers takes
> over:
> >
> >Since the security handlers depend on the DOM interfaces, they  cannot
> >work with pure OM instances. They expect DOM impls. So now there's a
> >need to switch from normal OM factory to DOM factory. Therefore
> >following method is proposed to to handle this.
> >
> >There will be some processing of the SOAPEnvelope before it reaches
> >the security handlers.
> >And there will be a reference to this partially built SOAPEnvelope in
> >the MessageContext object. This SOAPEnvelope consists only of pure OM
> >based elements (org.apache.axis.soap.*). Now we get the pull parser
> >from the SOAPEvelope we have through the OMStAXWrapper (This is used
> >to get the pull events from OMElements, irrespectiveof their build
> >state)
> >
> >PullParser pp = messageContext.getSOAPEnvelope().getPullParser()
> >//Returns a pp pointing to the start of the document
> >
> >Then we create a new StAXSOAPModelBuilder passing the DOMSOAPFactory
> >together with the pull parser returned from the SOAPEnvelope.
> >
> >StAXSOAPModelBuilder builder = new StAXSOAPModelBuilder(pp, new
> DOMFactory())
> >
> >At this point the SOAPEnvelope reference in the message context is
> >pointing to the older pure OM based SOAPEnvelope.
> >This will have to reassigned to the new OM+DOM based SOAPEnvelope, as
> >shown below:
> >
> >messageContext.setEnvelope(builder.getDocumentElement()); // This will
> >set the reference to the new DOMSOAPEnvelopeImpl
> >
> >Therefore to achieve this we need to have remember the following point
> >as a best practise : DON'T POINT TO THE SOAP ENVELOPE OF A MESSAGE,
> >JUST POINT TO THE MESSAGE_CONTEXT ONLY.
> >
> >I think this is one of the best use cases which shows the beauty of
> >the Factory and Builder concept used in Axis2 - OM design :)
> >
> >Thanks,
> >Ruchith
> >
> >
> >
> 
> 
> --
> The best way to predict the future is to invent it - Alan Kay
> 




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