On 11/3/06, Frank Budinsky <[EMAIL PROTECTED]> wrote:
Simon,
The Sequence entry returns a special property:
if (sequence.getProperty(i) == specialCDataProperty) {
String cDataValue = sequence.getValue(i);
}
The problem is that this special property is currently inherited from the
underlying EMF, so it's really not something we want clients to use. RIght
now, this works fine in terms of reading in CDATA and not losing it when
you reserialize, but there's really no proper way for an SDO client to
actually access it. Without using EMF apis, the only way a client can
decide that an entry is CDATA is by looking at the property name (and hope
there's no real property with that name). Longer term, I'm not sure that
even handling it this way is right. Maybe CDATA and other special XML
things should look like mixed text in the sequence (property == null), and
some XMLHelper method (or some Tuscany specific API for now) could be used
to check if it's actually something special like CDATA. Maybe you should
try to do something like that in the C++ impl, and if it looks promissing,
we'll switch the Java impl to do the same.
Frank
"Simon Laws" <[EMAIL PROTECTED]> wrote on 11/03/2006 10:18:04 AM:
> On 11/3/06, Frank Budinsky <[EMAIL PROTECTED]> wrote:
> >
> > In the Tuscany Java implementation we expose CDATA as sequence entries
> > (like mixed text) with a special "CDATA" property (we handle comments
in a
> > similar way). SDO doesn't define a special property for CDATA, so this
is
> > an implementation-specific feature. I'm not sure, long term, what
should
> > be the best (proper) way to do this.
> >
> > Frank.
> >
> > "Simon Laws" <[EMAIL PROTECTED]> wrote on 11/03/2006 09:41:25
AM:
> >
> > > On 10/26/06, Simon Laws <[EMAIL PROTECTED]> wrote:
> > > >
> > > > This is primarily a C++ question but I guess could apply to Java
also.
> > I'm
> > > > trying to read a document into C++ SDO that contains a CDATA
section.
> > The
> > > > corresponding CDATA doesn't make its way into the resulting SDO. I
put
> > the
> > > > C++ SDO implementation in the debugger and found the reason why:
> > > >
> > > > sax2parser.cpp
> > > >
> > > > void sdo_cdataBlock(void *ctx, const xmlChar *value, int len)
> > > > {
> > > > }
> > > >
> > > > So the callback exists, gets called with the correct data during
the
> > > > parse, i.e. LibXML2 is doing the right thing, but the callback is
> > ignored.
> > > > Is there a good reason for this? I did a quick search of the C++
and
> > Java
> > > > specs and they don't appear to discuss CDATA specifically. Can
someone
> > > > comment on whether the Java implementation handles CDATA
successfully?
> > > >
> > > > Logically, from an SDO point of view, there is probably no need to
> > treat
> > > > CDATA specially as the SDO model dictates precisely the difference
> > between
> > > > data and structure. We may find that to make the XML DAS function
work
> > we
> > > > have to know that a property potentially contains markup but I'd
have
> > to
> > > > look closely at how the C++ SDO implementation of the XML DAS
function
> > > > streams out SDOs to XML when requested to do so.
> > > >
> > > > If CDATA hasn't been omitted for a good reason I'll come up with a
> > > > proposal for C++ SDO.
> > > >
> > > > Regards
> > > >
> > > > Simon
> > >
> > >
> > >
> > > I didn't get any response to this. Here are my further thoughts..
> > >
> > > There are a number of options for representing CDATA in SDO, for
example
> > >
> > > 1) Duplicate the CDATA string as is, including the "<![CDATA[" and
"]]>"
> > > markers, to the appropriate property in the data object hiearchy
> > > 2) Duplicate the CDATA string excluding the "<![CDATA[" and "]]>"
> > markers
> > > and instigate a special flag to indicate that CDATA is present.
> > >
> > > CDATA is the specific concern of XML, i.e. the chracter entities
that
> > CDATA
> > > protects an XML parser from are of no
> > > concern to SDO because SDO is not intended to be tied directly to
XML.
> > So
> > > given the example options above we
> > > either expose the specifics of XML to the SDO core 2) or to the SDO
user
> > 1).
> > >
> > > Neither are particularly attractive.
> > >
> > > 1) appears to be the simplest approach to implement because it
provides
> > a
> > > mechanism for the user to read, and
> > > create CDATA without having to provide much special support in SDO.
2)
> > is
> > > more involved particularly because
> > > CDATA can appear mixed in with other text strings and so a sequence
may
> > need
> > > to be used to represent properties
> > > that have a mixture of text and CDATA marking those sequences
entries
> > that
> > > are CDATA.
> > >
> > > 1) does require changes (at least in C++ SDO) because XML parsers
tend
> > to be
> > > too helpful in this case for
> > > processing CDATA. XML parsers, libxml2 in particular, recognize the
> > > "<![CDATA[" and "]]>" sequence as a special
> > > indicator and throw it away returning just the text it includes. We
> > would
> > > have to reintroduce it and store it in
> > > the parameter value in question. The C++ SDO implementation uses a
lot
> > of
> > > XML string handling before the parameter
> > > value is actually stored which URL encodes parts of the CDATA
markers so
> > > this would have to be fixed. When writing out the CDATA strings any
> > string
> > > typed properties would have to be scanned for the markers so that
the
> > > appropriate libxml2 functions can be called to get the CDATA
sections in
> > the
> > > right place.
> > >
> > > I have a test implementation of 1). If this is the way we want to go
I
> > would
> > > have to do more work to thread CDATA handling through the xml
strings
> > that
> > > are used to set parameters. Happy to do this but would like to
discuss
> > > first.
> > >
> > > Thoughts (particularly on what Java SDO does with CDATA)?
> > >
> > > Simon
> >
> >
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> >
> > Ok, thanks for that Frank. It would be nice for us to do it in the
same
> way so even though it is not in the SDO spec the implementations are
> similar. A question, how do you set a sequence entry to indicate that it
> holds CDATA. Is this a flag that is exposed on the sequence API. I'm not
> really familiar with the Java SDO code base. Can you give me a class
name to
> go look at?
>
> Simon
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Ok, thanks Frank. That explains why I couldn't really track it down in the
Java code. I'll have a bash at extending the C++ implementation I have now
and I'll report back.
Regards
Simon
