Re: [Saxdotnet-devel] StartElement, when URI is not present

[Karl W. <ka...@wa...>]

Elliotte Harold wrote:
> Karl Waclawek wrote:
> 
> 
>> I can understand this, but you would usually check the Uri anyway,
>> since you want to know if the name has a namespace. So you would
>> get used to "if (uri == null)" fairly quickly.
> 
> 
> In fact, I find that I don't do that nearly as often as you'd think. As 
> long as I know the URI is not null there are a lot of cases where I can 
> treat the empty space exactly the same as any other namespace. If I had 
> to worry about it being null, I absolutely couldn't do that and I'd have 
> to litter my code with a lot of null checks or catch 
> (NullPointerException). It just works out cleaner to be able to treat no 
> namespace the same as any other namespace. which I can do most (not all) 
> of the time if it's the empty string and none of the time if it's null.

I had another look at the Java API.
It seems it is quite inconsistent with respect to empty string vs. null.

Examples:

- In EntityResolver, all occurrences of publicId or baseUri
   are supposed to be null, when absent.

- DTDHandler.notationDecl(): publicId, systemId can be null,
   if not provided

- DTDHandler.unparsedEntityDecl: publicId can be null if not provided

- DeclHandler.attributeDecl(): mode and value can be null, where
   in the latter there is actually a semantic difference between
   value = null (meaning: none defined) and value = empty string
   (meaning: a value is specified, and it is the empty string).

- DeclHandler.externalEntityDecl: publicId can be null, if not provided

- LexicalHandler.startDTD(): publicId, systemId can be null,
   if not declared

It actually seems that the prevalent approach is to use null for absence 
of a string parameter, and only in the case of namespaces does the API
stray from this rule.

However, I would strongly suggest that we remain consistent in
SAX for .NET. If we pick String.Empty, then we need to allow one
inconsistency - and that is for the Value parameter passed to the
attributeDecl() call-back.


Karl