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RE: Maybe a newbie question: Awful OO software structure with

• To: <gbernd@g...>,<xml-dev@l...>
• Subject: RE: Maybe a newbie question: Awful OO software structure with SAX!?
• From: "Michael Kay" <mike@s...>
• Date: Mon, 30 Jan 2006 00:51:29 -0000
• In-reply-to: <9723.1138535249@w...>
• Thread-index: AcYkytHj/Dh2c/sKT3ysj5RjMsrrwwAa/+uQ

There are two architectures you can use that solve this problem, I've used
them both satisfactorily. One is to write a ContentHandler that multicasts
events to recipients who have registered themselves: typically a recipient
registers itself as interested in element X, and when an X arrives you mark
that recipient as active and send it all events until the matching
end-element. The other approach is more of a pipeline: each event is
processed by the first filter in the pipeline, which then (if appropriate)
passes it on to further filters.

Michael Kay
http://www.saxonica.com/ 

> -----Original Message-----
> From: gbernd@g... [mailto:gbernd@g...] 
> Sent: 29 January 2006 11:47
> To: xml-dev@l...
> Subject:  Maybe a newbie question: Awful OO software 
> structure with SAX!?
> 
> Hi,
> 
> I have a software project holding its configuration data in an XML
> structured file. Currently I'm using DOM to load this 
> configuration data and
> then kick off (instantiate) the relevant Java objects by providing the
> relevant DOM subtree to their constructor. Within each 
> management object,
> this hierarchical evaluation of the configuration data is 
> repeated as deep
> as necessary. For the example (see below), the "Evaluation" management
> receives the subtree below the <Evaluation>-node and provides 
> DOM subtrees
> to the "Plot_2D" and "Plot_3D" management objects when 
> instantiating them.
> 
> <Main>
> 	<General>
> 		...
> 	</General>
> 	<Evaluation>
> 		<Plot_2D>
> 			...
> 		</Plot_2D>
> 		<Plot_2D>
> 			...
> 		</Plot_2D>
> 		<Plot_3D>
> 			...
> 		</Plot_3D>
> 	</Evaluation>
> </Main>
> 
> When using the DOM concept, I like that each management 
> object (General,
> Evaluation, Plot_2D, Plot_3D...) is responsible for parsing 
> its own section
> of the configuration file. This reflects the OO software 
> approach of putting
> the code to the data and simplifies code maintenance.
> 
> Now, due the problem of determining line numbers in DOM, I'm 
> considering
> using a SAX parser. But when reading the SAX tutorials, I'm 
> horrified. All
> examples show one centralized event handler, which knows 
> about all keywords
> and dispatches the values to the JAVA objects.
> 
> This is against all OO approaches and requires changes in a 
> central module
> each time a subsection of the configuration data is made. Now 
> my question:
> Is this the intended way of using SAX? Or is there a way of 
> forwarding the
> SAX-events to sub-eventhandlers located in the management 
> objects, which I
> didn't find yet?
> 
> With kind regards
> Bernd
> 
> -- 
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