Re: [xml-dev] SAXException, checked, buy why?

[Alan Gutierrez <alan-xml-dev@engrm.com>]

* Karl Waclawek <karl@waclawek.net> [2005-01-03 11:14]:
> Alan Gutierrez wrote:
> 
> 
> >>Maybe in that case event handlers should avoid throwing
> >>exceptions at all, and rather notify an error handler.
> >
> >
> >    Agreed.
> >    
> >    Please consider my idea again.
> >
> >    Assume at the SAX content handler author, and the SAX
> >    application author are two different entities. That the SAX
> >    content handler cannot anticipate how exceptions should be
> >    handled.
> >
> >    What is the design of an API for exception handling within the
> >    content handler? Within the observer of an observer pattern?
> >
> >    I proposed on in an earlier message:
> >
> >    public interface SAXCassandra {
> >        public void error (SAXError saxError);
> >    }
> 
> What makes this different from the ErrorHandler interface
> already specified in SAX?

    public interface ErrorHandler {
        public void error(SAXParseException exception)
            throws SAXException;
        public void fatalError(SAXParseException exception)
            throws SAXException;
        public void warning(SAXParseException exception)
            throws SAXException;
    }

    It is meant to respond to errors in parse, not errors in content
    handling. If content handler authors were to adopt it for use as
    a means to intercept genral errors, they'd be going against the
    documented use.

    http://www.saxproject.org/apidoc/org/xml/sax/ErrorHandler.html

> >    By implementing this observer, and handing it off to a content
> >    handler, the application developer can inspect errors before they
> >    are thrown.
> >
> >    The sax filter author writes:
> >
> >    public void startElement(
> >        String ns, String ln, String qn, Attributes as
> >    ) {
> >      if (ln.equals("foo")) {
> >        FileInputStream in = null;
> >        String fileName = as.getValue("file-name");
> >        do {
> >          try {
> >            in = new FileInputStream(new File(fileName));
> >          } catch (FileNotFoundException e) {
> >            this.cassandra.error(new SAXError(e));
> >          }
> >        } while (in == null);
> >      }
> >    }
> >
> >    The above probably wouldn't give the application author enough
> >    information to recover from the error, but we can fix that by
> >    creating a special SAXError, or wrapping a Foo specific
> >    exception that includes the file name.

> All agreed, but see my question above.
> (Maybe I am still slow on the uptake because I celebrated too
> much on New Year's eve ;-) )

    No. You're asking the questions I asked myself.
    
--
Alan Gutierrez - alan@engrm.com