[news.eclipse.tools.emf] Re: Add xsi:type hint to element during load

[johntimm@xxxxxxxxxx (John T.E. Timm)]

Ed:

I chose DOM as it is random-access and allows me to "peek" at element 
children to determine how to decorate with xsi:type. I was thinking of 
overriding other load methods (InputSource, InputStream) to use DOM as 
well.

Ed Merks wrote:

> John,

> Comments below.


> John T.E. Timm wrote:
> > I have a situation where I would like to add xsi:type information when 
> > I load an XML document before it gets materialized into an Ecore 
> > object model.
> >
> > <elementA>
> >   <!-- no id element corresponds to instance of ClassA -->
> >   ...
> > </elementA>
> >
> > <elementA>
> >  <!-- id element indicates that elementA corresponds to instance of 
> > ClassA subclass -->
> >  <id value="1.2.3"/>
> >  ...
> > </elementA>
> Something needs to be constructed as soon as <elementA> is seen.  It 
> can't wait until other nested elements are processed.
> > The input format may not contain the xsi:type hints for subclasses as 
> > it may have been produced outside of EMF. However, if elementA 
> > corresponds to an instance of ClassA, then elementA with an id element 
> > directly underneath it corresponds to a subclass of ClassA. What I 
> > need to do is intercept the parsing mechanism and add the xsi:type 
> > attribute depending on the value of the id element. 
> Easier said then done...
> > My initial approach is to create a subclass of XMLLoadImpl that 
> > overrides traverse and traverseElement to inspect children of element 
> > nodes and determine whether I should create type hint before handing 
> > control over to super.traverse/traverseElement. Is there a better way 
> > to accomplish this through a different extension mechanism?
> I would have expected overrides of the XMLHandler, but it sounds like 
> you expect always to create directly from DOM...
> > Additionally, I will have a registry that maps id's to fully qualified 
> > class names. Given a class name, what is the best way to find the 
> > correct EPackage and get the prefix and nsURI?
> EClass.getEPackage().getNsURI().

> Given that you need to process a nested element to decide how to process 
> <elementA> I think it's very tough.  I don't know how to do that...  An 
> xsi:type is always an attribute that can be processed as the opening 
> element bracket is processed...
> > Thanks,
> >
> > JT