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   RE: [xml-dev] SAX and Pull options: was: Penance for misspent attributes

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Bill de hOra wrote,
> If XMLPULL was a bespoke framework instead of a proposed public API, 
> replace typecode with polymorphism is one the first refactorings 
> that would come to mind. you could have something like
> this: 
>   XmlPullParser xpp = factory.newPullParser();
>   xpp.setInput (reader);
>   xpp.accept(new XMLPullVisitorImpl());
> where:
>   class XMLPullVisitorImpl() implements XMLPullVisitor
>   {
>     public void visit(Start s); 
>     {System.out.println("START_TAG:"+s.getName());}
>     public void visit(StartTag s) 
>     {System.out.println("END_TAG:"+s.getName()}
>     public void visit(Text s) 
>     {System.out.println("TEXT:"+s.getText()}
>   }


  void visit(Start s)

isn't much more than a respelling of,

  void startElement(String ns, String ln, String qn, Attributes a)

so isn't this just a recapitulation of the SAX API, but with an
unnecessary detour through XPP? FWIW it's, IMO, good practice _not_ to 
overload visitor methods, but instead differentiate on names, eg.,

  public void visitStart(Start s)
  public void visitStartTag(StartTag s) 
  public void visitText(Text s) 

in which case the equivalence is even more obvious.

As you said earlier SAX is, in effect, a Visitor based API. The
converse is also true: Visitor based APIs are, in effect, event 
driven. That being so, if you're comfortable with the Visitor pattern 
then you might as well simply use SAX directly.




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