Re: Resolving tag location during call to createElement() in a customDocumentImpl

[Maitreyee Pasad <pa...@gst.com>]

John:

Did you consider using the SAX Parser to create the DOM on your own?
In that case you will have a call back when an element goes out of scope.

We have implemented something similar to that approach using a stack like you
mentioned.

Maitreyee

oshea2j@ie.ibm.com wrote:

> Hi,
>   I'm extending the Xerces DocumentImpl class and using the parser property
> http://apache.org/xml/properties/dom/document-class-name to get the XercesJ
> parser to use my implementation class when parsing the XML document.  In
> conjunction, I've written a collection of classes which extend the base
> ElementImpl class and provide application level APIs for manipulating the
> XML document.  On calls to DocumentImpl.createElement() from the parser, my
> DocumentImpl chooses an ElementImpl, instanciates it, and returns it to the
> parser.  The parser then inserts it into the DOM.  Once parsing is
> complete, I have a DOM which is also a set of related objects which
> implement a set of application level interfaces.  These application level
> interfaces allow navigation and manipulation of the underlying data without
> exposing XML or DOM (The reason for doing this is the application API
> framework is generic and is also implemented using other
> technologies/transports.
>
>   This is all well and good but I've hit a snag when overriding
> DocumentImpl.createElement().  The parser just gives me the tag name the
> parser has just encountered and expects an ElementImpl in return.  However,
> the initialization required for my custom ElementImpl instances for each
> tag name depends on *where* in the XML document the tag is located.
>
> Let me give an example:
>
> <person>
>   <name>
>       <first>XXX</first>
>       <last>YYY</last>
> </person>
>
> <car manufacturer="Mercedes">
>   <name>500SEL</name>
> </car>
>
> I have two classes which represent Elements with the tag <name> - one for
> People and one for Cars.  Each provides a set of application APIs for
> accessing the name of that type of object.  However, during parsing, my
> DocumentImpl cannot distinguish between a "person/name" and a "car/name" so
> it can't tell which type of ElementImpl to create.  (You may say this
> example uses bad XML Schema/DTD design but it does illustrate the problem
> I'm confronted with.  I need to be able to cater for cases where such tag
> name collisions occur in the underlying XML data.)
>
> So is there any way for my DocumentImpl to determine, during the parsing
> phase, where in the document the current tag is?  Ideally Xerces would give
> me an XPath string instead of just the tag name - that would solve my
> problem but it doesn't seem to be the case :(   Has anyone got any
> suggestions as to a viable alternative?  I thought about implementing a
> stack inside my DocumentImpl to keep track of the elements the parser is
> creating but there is no callback to indicate when a tag scope is closed,
> allowing me to pop that tag off the stack.
>
> Any suggestions welcome!
>
> j
>
> John O'Shea,
> Phone : + 353 1 8154228       Email : oshea2j@ie.ibm.com
>
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