Check XML for well-formedness using SAX

[Urs Muntwyler]

Hi there

I have to check if the content of a file is a well-formed XML document. Since the XML documents can be large, I'm using SAX to perform this task.

Using Java, my code looks (somehow) like this:

public void checkForWellFormedness(File file)
{
SAXParser saxParser;
DefaultHandler dh;
// init parser
try {
SAXParserFactory spfactory = SAXParserFactory.newInstance; saxParser = spfactory.newSAXParser; dh = new DefaultHandler; } catch(Exception e) { System.out.println("Cannot initialize SAX parser."); e.printStackTrace; } // parse the XML document using SAX parser try { saxParser.parse(file,dh); // SAXException, IOException } catch(SAXException se) { // (*) // only invoked in case of fatalError // what if error occur? Is the XML document well-formed? System.out.println("Document is not well-formed."); se.printStackTrace; } catch(IOException ioe) { System.out.println("Cannot read file."); ioe.printStackTrace; } }

In the above code, you can see that I'm using the DefaultHandler class, which implements the ErrorHandler interface. In this class, the default implementation of fatalError throws a SAXParseException, which I'm catching in the above catch block (*). The default implementation of error does nothing, i.e. it does not throw a SAXParseException. (I know what to do if I want that behaviour:
subclass DefaultHandler and overwrite the method).

My question is simple: what does it mean to have a well-formed XML document? Does it mean to have no fatalError occurring during parsing (which means that the above code is ok), or is an XML document well-formed if no fatalError AND no error occur? (which means that I have to subclass DefaultHandler and overwrite method error to throw a SAXParseException so it is catched in the catch-block (*)).

Thanks for your help!

 

[Johannes Koch]

My question is simple: what does it mean to have a well-formed XML document? Does it mean to have no fatalError occurring during parsing (which means that the above code is ok),

AFAIK well-formedness errors are fatal errors.

 

[Martin SChukrazy]

A quick way to check for well-formedness of an xml document is to use internet explorer.