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From Erik Hatcher <e...@ehatchersolutions.com>
Subject Re: "Advanced" query language
Date Fri, 16 Dec 2005 09:01:40 GMT
Why wouldn't simply using DOM be sufficient?   Is it envisioned that  
a query XML would be large enough to prohibit RAM DOM loading of the  
entire document?

	Erik


On Dec 16, 2005, at 2:51 AM, mark harwood wrote:

>> While SAX is fast, I've found callback interfaces
>> more difficult to
>> deal with while generating nested object graphs...
>> it normally
>> requires one to maintain state in stack(s).
>
> I've gone to some trouble to avoid the effects of this
> on the programming model.
> Stack management is handled by the parser and the
> builder at each level in the stack can delegate
> control and consume output of delegate builders
> without maintaining complex state.
> For example, the builder for FilteredQuerys has to
> handle this:
> <FilteredQuery>
>  <Filter>
>   <RangeFilter fieldName="price" lowerTerm="10"
> pperTerm="20"/>
>   </Filter>
>  <Query><TermQuery field="contents"
> value="car"/></Query>
> </FilteredQuery>
>
> To delegate control to any choice of filter or query
> parser builder and consume its output it simply does
> this:
>
> if (localName.equals("Filter")) {
>  parser.delegateChildElements(new
> ObjectBuilderFinder(),
>    new ObjectConsumer() {
> 	public void setObject(Object objectValue) {
>           filter = (Filter) objectValue;
> 	}
> });
>
> It looks like procedural code calling, then setting
> instance data ("filter") but is actually still all
> event based SAX under the covers.
>
> Cheers
> Mark
>
>
> 		
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