SAX2 RFD: Inheritance vs. Modification vs. Amalgamation
(I'd like to hear from as many people as possible on this issue.) For SAX2, we need to add at least four methods to the SAX 1.0 Parser interface: public void setFeature (String featureId, boolean state) throws SAXException; public boolean getFeature (String featureId) throws SAXException; public void setProperty (String propertyId, Object value) throws SAXException; public Object getProperty (String propertyId) throws SAXException; There are three ways of doing this: 1. Create a new interface, org.xml.sax.Parser2, that extends org.xml.sax.Parser. PRO: - provides nice, two-way compatibility - easy to write adapters for existing SAX 1.0 drivers. CON: - subclassing always leads to crime (see the GOF book for copious warnings). 2. Add the methods to org.xml.sax.Parser, and require applications to catch NoSuchMethodException when using the new methods, in case they're concerned about what version they're dealing with. PRO: - doesn't limit options for subclassing in the future CON: - very difficult to write adapters for existing SAX 1.0 drivers (slower acceptance and implementation of SAX2) - can cause unexpected behaviour at deployment time, unless the application designer knows to catch NoSuchMethodException 3. Create a separate interface org.xml.sax.ParserProps (or something like that), and require SAX2 drivers to implement both interfaces. PRO: - easy to writer adapters for existing SAX 1.0 drivers - fewer nasty deployment surprises CON: - will require lots of casting - conceptually ugly Please, comment, comment, comment! I'm not smart enough to figure this out myself. All the best, David -- David Megginson david@m... http://www.megginson.com/ xml-dev: A list for W3C XML Developers. To post, mailto:xml-dev@i... Archived as: http://www.lists.ic.ac.uk/hypermail/xml-dev/ and on CD-ROM/ISBN 981-02-3594-1 To (un)subscribe, mailto:majordomo@i... the following message; (un)subscribe xml-dev To subscribe to the digests, mailto:majordomo@i... the following message; subscribe xml-dev-digest List coordinator, Henry Rzepa (mailto:rzepa@i...)
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