[castor-user] Use Castor or Xerces to validate arbitrary XML??

[Lauren Bish]

There is a particular XML blob in our SOAP messages - the structure of 
which is defined at runtime. I have to write logic to validate the 
structure and values of this blob - currently it is just mapped into a 
name/string value pair in a list. I have a class that has a list of 
elements which define what the structure and values should be, including 
min/max occurances and so on.

So, I was thinking of generating an XSD on the fly from the class which 
defines the structure and other contraints, then using that XSD to 
validate the XML of the blob. We use Castor (XML) and Xerces, and I was 
wondering which would be better to use to perform this validation.

I don't necessarily want to generate classes usingthe Schema compiler of 
Castor just to validate the XML as the name/string value list is working 
well for us with regards to using the arbitrary info from that XML (I 
use it in combination with the class which defines the structure to 
generate a GUI on the fly which lets the user enter/edit the values).

For now, I just want to validate on the server backend that the XML the 
client sends us matches the Schema as defined in the class which has the 
list of elements (and their types and contraints).

I found this online:
http://www.javaworld.com/javaworld/jw-12-2001/jw-1228-jaxb-p2.html
but it assumes that I would want to compile the Schema using Castor 
Schema compiler. And this:

http://www.onjava.com/pub/a/onjava/2004/09/15/schema-validation.html
which also makes assumptions about Xerces (external static XSD file)
What I am thinking I need is something that I can create/set, that holds 
a Schema definition (optionally writing it out to a file would be okay) 
that can be fed into a class (supposedly a parser), that will give me 
meaningful feedback on whether the XML is valid according to the Schema.

Any ideas/suggestions? Examples?
TIA