SAX RFD: ModSAX Predefined Features

David Megginson david at
Mon Mar 8 19:52:05 GMT 1999

John Cowan writes:
 > David Megginson wrote:
 > >   public abstract void setFeature (String featureID, boolean state)
 > >     throws SAXNotSupportedException;
 > I want to propose a restriction and an extension:
 > 1) This method cannot be called after any other parser method
 > has been invoked.

Wouldn't it be better to allow the parser/filter make that decision?
If the user attempts to change something during a parse that should
*not* be changed during a parse, the parser/filter can throw a

 > 2) This method is allowed to throw a SAXNewParserException, which
 > encapsulates a replacement parser.  The application should use
 > the parser inside the exception in place of the original parser.
 > This allows parsers to push filters on top of themselves, which
 > complements the ability of applications to push them.

I think that this could be layered on top of SAX, simply by
subclassing SAXNotSupportedException.

All the best,


David Megginson                 david at

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