Facets

["Nacho G. Mac Dowell" <ig...@informa.es>]

I was wondering if enumerations and patterns and so on should be 
implemented at runtime (on the Impl class) or when 
unmarshalling/marshalling. If Enumerations are used they probably should 
be considered as "virtually different types"  than their base type. This 
would make the Impl classes safe type. I was thinking if it would be 
nice to actually implement an Enumeration pattern class. Is this 
considered in JAXB spec? Is it up to the implementors? What do you 
think? Could EnumerationSG, PatternSG... be considered as types? In xml 
schema the aren't, but since java is supposed to be safe type...

regards,

Nacho G. Mac Dowell

PD: I saw that SimpleTypeSG has a addValidation method. Is it for this 
purpose?

 

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Re: Facets

[Jochen Wiedmann <jo...@freenet.de>]

Nacho G. Mac Dowell wrote:

> I was wondering if enumerations and patterns and so on should be 
> implemented at runtime (on the Impl class) or when 
> unmarshalling/marshalling. If Enumerations are used they probably should 
> be considered as "virtually different types"  than their base type. This 
> would make the Impl classes safe type. I was thinking if it would be 
> nice to actually implement an Enumeration pattern class. Is this 
> considered in JAXB spec? Is it up to the implementors? What do you 
> think? Could EnumerationSG, PatternSG... be considered as types? In xml 
> schema the aren't, but since java is supposed to be safe type...
> 
> regards,
> 
> Nacho G. Mac Dowell
> 
> PD: I saw that SimpleTypeSG has a addValidation method. Is it for this 
> purpose?

The "addValidation" method is, of course, on purpose: It's purpose is 
just what you would expect: To add validation code to the Impl class.

The JAXB specification requires validation only when unmarshalling. Of 
course, if the Impl class validates, then the unmarshaller validates 
automatically as well, so that's absolutely fine with the SPEC.

IMO, the answer to "When should I validate" should not be general: It 
depends on the facet.

For example, facets like "minExcludes" can easily be checked in the
Impl class and so they should be checked there.

Facets like "minOccurs", or "maxOccurs", cannot always be checked by the 
impl class: If (as specified by JAXB) a list property is implemented by 
a list, to which the user has full access, then the impl class doesn't 
have actual control. In that case the unmarshaller must validate. 
However, if the property is implemented with "getFoo" and "setFoo" (or 
"addFoo") methods, then validation in the impl class is fine again.

Enumerations can be validated by the impl class (at least I believe so 
:-) and, if I remember right, they currently are.

Finally, patterns are a completely different story: First of all, 
patterns are a restriction of the *lexical representation* of the data. 
For example, consider an int type and a pattern, which requests, that 
the data contains four digits. This can easily be checked by the 
unmarshaller (because he *has* the lexical representation). However, it 
cannot easily be checked by the impl class: We as humans know, that the 
allowed value set can be expressed with minIncludes and maxIncludes. 
However, that information is almost impossible to derive from the 
specified pattern.


Jochen

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