Re: [xml-dev] Best way to create an XML document

[Michael Glavassevich <mrglavas@ca.ibm.com>]

"Mukul Gandhi" <gandhi.mukul@gmail.com> wrote on 04/13/2008 12:59:56 PM:

> On Sat, Apr 12, 2008 at 2:19 PM, Andrew Welch <andrew.j.welch@gmail.
> com> wrote:
> >  Alternatively use the streaming api in Java 6 - see XMLStreamWriter.
>
> I tried using XMLStreamWriter (I guess this is a StAX interface).
>
> As for the well-formedness requirement, I think this is better than
> the SAX calls (the program I posted earlier in this thread).
>
> Please consider this example:
>
> XMLOutputFactory factory = XMLOutputFactory.newInstance();
> XMLStreamWriter writer = factory.createXMLStreamWriter(System.out);
> writer.writeStartDocument();
> writer.writeStartElement("x");
> writer.writeStartElement("y");
> writer.writeAttribute("attr1", "123");
> writer.writeEndDocument();
> writer.flush();
> writer.close();
>
> This produces the output (as intended by me):
>
> <?xml version="1.0" ?><x><y attr1="123"></y></x>
>
> I think it's hard to create ill-formed XML output with
> XMLStreamWriter. Or, can we?

It keeps the tags nested properly but you can still write all sorts of
garbage.

Extending your example (spot the errors):

writer.writeStartDocument();
writer.writeDTD("<!GARBAGE>");
writer.writeComment("bad -- comment");
writer.writeStartElement("x");
writer.writeCharacters("\u0000");
writer.writeProcessingInstruction("xml", "version=\"1.0\"");
writer.writeStartElement("y");
writer.writeAttribute("attr1", "123");
writer.writeAttribute("attr1", "456");
writer.writeEndElement();
writer.writeEndElement();
writer.writeEmptyElement("3");
writer.writeEndDocument();
writer.flush();
writer.close();

produces:

<?xml version="1.0" ?><!GARBAGE><!--bad -- comment--><x><?xml
version="1.0"?><y attr1="123" attr1="456"></y></x><3/>

with a NUL char after <x>.

> But the Java docs say - "The XMLStreamWriter does not perform well
> formedness checking on its input". What does this mean?

It means what it says. It doesn't check that the document you're writing is
well-formed.

> Can we pretty print the XML output with StaX?

Depends on the implementation. There's no standard property in the StAX
spec for that.

> Can we use StaX with JDK 1.4, in a stable manner? I need to run this
> on a PC where I cannot upgrade to JDK 1.6.x.

Sure if you can find an implementation which will run on JDK 1.4. Woodstox
[1] maybe? Xerces [2] eventually. There's no such limitation in the API.
Last time I checked none of the signatures in javax.xml.stream required
more than JDK 1.2.

> --
> Regards,
> Mukul Gandhi
>
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[1] http://woodstox.codehaus.org/
[2]
http://svn.apache.org/viewvc/xerces/java/branches/stax-dev/src/org/apache/xerces/stax/


Michael Glavassevich
XML Parser Development
IBM Toronto Lab
E-mail: mrglavas@ca.ibm.com
E-mail: mrglavas@apache.org