[Simple-support] ElementUnion and xs:any

[João M. G. <jm...@gm...>]

Hi Niall, all,
I started using SimpleXML recently in an open source project
(https://github.com/societies/). We started out using JAXB but due to
a number of problems of JAXB on Android are attempting a move to
Simple. Today I came across two problems. The first one is regarding
using Simple in environments with multiple ClassLoaders, such as an
OSGi container. I didn't fully study the problem, will do so in the
next few days since it is not a show stopper for us. I'll keep you
posted.

Regarding the second problem is the use of element union. We were
using JAXB because we wanted to be XML-centric (schema) rather than
Java-centric. Our data model for communication would be designed in
pure XML so that it could (theoretically) be used in any language.
Happens that we have "xs:any" in a few places. From what I've gathered
from Simple documentation, this would map to have an Object field
annotated with @ElementUnion. However, this places a dependency in the
containing types to the contained types:

@ElementUnion({
   @Element(name="circle", type=Circle.class),
   @Element(name="square", type=Square.class)
})

This is not acceptable for us as we want to keep the Java data model
clean, consistent with the schema. If the dependency is not in the
schema it should not be in the Java version either. For the same
reason the explicit indication of the class as an attribute (<any
class="foo.bar.X">) is also not a good solution. One good solution for
us would be supporting the (de)serialization of a non mapped class
to/from a generic XML element, such as org.w3c.dom.Element, as
supported by JAXB.

Any thoughts? I am available to contribute to Simple regarding this
issue if you want our help.
Cheers,
João