Jim Beard wrote:
>
> Howdy all,
>
> I work with a company that is trying to use JAX-B generated code in
> a number of projects. The most recent one involves a rather complex set
> of Schemas. In these Schemas there are complexTypes defined using
> extension from other complexTypes. Some of these complexTypes are based
> off of other complexTypes using restriction. XmlSpy validates
> everything, as does a recent SAX parser. However xjc spits out errors
> when I try to use JAX-B to generate code from the Schemas, and no code
> is generated. The errors look like this:
>
> [ERROR] Base complex type is derived by restriction, while this complex
> type is derived by extension
>
> This problem occurs 5 or so times throughout the Schema. We have a
> little bit of control over the Schema we are using ( though another
> company is mainly responsible for it ). However we have no control over
> the base Schemas that this Schema uses in its namespace.
> I tried running with '-extension' and adding in the
> complexTypeSubstitution attributes, but still no luck. Does anyone have
> any experience with this problem or any advice to offer?
>
> NOTE: I found a work around now by swapping the extension and
> restriction elements of the complexTypes, so the that our base type uses
> extensions and the final type is a restriction. This seems to work.
> However, it is not an optimal solution due to the fact that it changes
> the approach of what types of data elements are being defined in which
> Schemas.
>
> I have been reviewing section 3.4.6 of the w3c Schema specifications
> to see if this is a problem with our Schemas, or with JAXB. Anyone have
> an opinion on this matter?
>
Hi Jim,
From what you've described, it does not sound like there is anything illegal
in your schemas. The problem is that this type of schema derivation hierarchy
is very difficult to map to a Java object inheritance hierarchy. Java has
no concept of "derivation by restriction" - roughly speaking, there is no way
for a sub-class to only inherit a portion of it's baseclass. The JAXB spec
(sec 5.3.2) sort of glosses over this issue because there really isn't a good
solution. It covers simple derivation by restriction, but handling a type
that derives by extension from a type that derives by restriction is a whole
other beast. As a result, the RI punts on the issue and flags it as an error.
It sounds like you might have enough wiggle-room in your schemas to work
around the issue though.
Thanks,
--Ryan
> Jim Beard
> counterclaim.com, Inc
> http://www.counterclaim.com
> http://openefm.sourceforge.net
> (800) 264-8145
>
>
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