[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Re: Yet another SAX2 observation
Yet another SAX2 observationActually, my preferred solution to this particular problem is not to offer _two_ representation of the namespace scoping information ... it'd be to use only the "xmlns*" attributes. Those start/end mapping calls haven't been useful to me at all. And on the contrary, the need to deal with two representations of the mapping scopes (which may or may not duplicate the info in the other representation) has been an annoyance. It's worth noting that while versions of stuff like LexicalHandler and DeclHandler have been around for 18 months or so (for anyone who has really been tracking "SAX2" discussions ;-) the namespace support hasn't been as discussed -- or implemented -- as long. The three different modes of namespace support are what I find to be the most problematic part. Particularly when controlled by two separate feature flags, and so there are four states -- one of which has been declared illegal ("false, false"). And keep in mind that those two flags control several other features beyond use of the start/end mapping calls. - Dave ----- Original Message ----- From: Box, Don To: 'xml-dev@x...' ; 'David Megginson (E-mail)' Sent: Sunday, March 12, 2000 6:36 PM Subject: Yet another SAX2 observation In trying to properly implement the in-scope namespaces Infoset property, I found the following inconvenience with SAX2. The ordering of startPrefixMapping and startElement requires the implementation of ContentHandler to either (a) create a new "scoping context" for each namespace declaration or (b) keep a data member around to note that a new element has started. The current docs regarding calling NamespaceSupport.pushContext at every startElement notification doesn't work. Assume the following implementation of ContentHandler: class me implements DefaultHandler void startPrefixMapping(String p, String u) ns.declarePrefix(p, u); } void startElement(...) ns.pushContext(); } void endElement(...) ns.popContext(); } } This implementation chokes, since the pushing needs to happen at the first startPrefixMapping, not at the startElement notification. Rather, to implement this correctly, one must write the code as follows: class me implements DefaultHandler void startPrefixMapping(String p, String u) ns.pushContext(); ns.declarePrefix(p, u); } void startElement(...) // do nothing wrt context mgmt. } void endElement(...) // do nothing wrt context mgmt. } void endPrefixMapping(String p) ns.popContext(); } } I have a feeling this isn't what people had in mind. I actually think the flaw is in ContentHandler, since the current design requires the implementation to retain additional state in order to match up namespace declarations with the elements they correspond to. DB http://www.develop.com/dbox *************************************************************************** This is xml-dev, the mailing list for XML developers. To unsubscribe, mailto:majordomo@x...&BODY=unsubscribe%20xml-dev List archives are available at http://xml.org/archives/xml-dev/ ***************************************************************************
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