Building DTD-compliant DOM

[John Robert Gardner <Jo...@east.sun.com>]

Again a question re. Xerces, and as I don't work with it enough to be on that 
list, please forward it as need be if that's a better forum.  I'm sure someone 
has looked at this before.  My colleague and I have looked for something like 
this in archives and Faq's, but to no avail.

<snip>
Okay, the crux of the question is:

In Java, using Xerces, how do you build, from scratch, a DOM tree that is
compliant with a specified DTD?

What I am doing is this: I'm creating my DOM tree, appending the elements,
and writing it out to a file. I thought the DOM tree is supposed to be
compliant with the DTD I specified in my DocumentType object, because I
constructed it with a reference to my DocumentTypeImpl object:

outDoc = new DocumentImpl(dti); // dti is my DocumentTypeImpl

Further, when I spit out the document, it does NOT contain a reference to my
DTD -- shouldn't it be doing that?

Do I have to manually order the elements to be compliant with my DTD? If so,
how can I get access to the DTD itself to find out the order of the
elements? In the older (1.1) IBM4J parser, there was a DTD class that you
could use to find out the specification of the element order. In the Xerces
parser, I see no access to the DTD whatsoever.

I have attempted to use SAX, but abandoned the effort because I need
non-linear access to an original document (this effort is following
references that could be referenced in any order, I need to have
random-access to the document).

So -- any thoughts?

</snip>

another tyvmia,

jr

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John Robert Gardner
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Re: Building DTD-compliant DOM

[Sean Kelly <ke...@mail2a.jpl.nasa.gov>]

John:

Try this:

Document toss = new DocumentImpl();
DocumentType docType =
toss.getImplementation().createDocumentType("rootElem",
    "-//XYZ//DTD My Special DTD//EN", "http:...");
Document doc = toss.getImplementation().createDocument(null, "rootElem",
docType);

If you serialize doc at this point, you'll get:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE rootElem PUBLIC "-//XYZ//DTD My Special DTD//EN"
    "http://my.host/whatever.dtd">
<rootElem/>

That "null" argument to createDocument is the namespace URI.  Set it if
you're using namespaces.

In my own projects, I hide calls to the *Impl classes in a general XML
service wrapper, so that the XML implementation can change withouth
affecting clients, so that first line goes away and becomes

Document toss = XML.createDocument();

(And in fact, there's an XML.createDTDDoc(...) method, too.)

Now, as for creating the doc nodes so they're compliant with the DTD ...
write careful code!  :-)  Well, seriously, I've never done that part before.
I also recall querying the DTD with XML4J, but I don't know how to do that
with Xerces either.

Good luck.
--Sean