Castor should infer types when unmarshalling

Werner as discussed previously, I'll make an attempt at a patch for this when I have time.

Castor should be smart enough, when unmarshalling, to distinguish which Class to instantiate when more than one <map-to> element in a mapping for two or more Classes have the same "xml" attribute value. Essentially, the unmarshaller should infer teh class to set into: unmarshal.setClass(<most appropriate>.class)

See below for an instance of the problem:

<class name="com.some.domain.Wallet">
   <map-to xml="Wallet" />
   <!-- Bunch of properties -->
</class>

<!--
    Wallet that has special properties used to facilitate marshalling
    which is not easily achieved using just the plain Domain objects
-->
<class name="com.some.domain.WalletFlexFacade"
   extends="com.some.domain.Wallet">
   <map-to xml="Wallet" />
   <field name="expenseRequests" collection="collection"
       type="com.some.domain.flex.ExpenseRequestFlexFacade">
       <bind-xml name="ErLine" />
   </field>
</class>

I then unmarshal some XML that has the <ErLine> elements in them like so:

String _MAPPING = XMLMapper.class.getResource("/resources/mapping/DomainObjectsMapping.xml").toExternalForm();
Mapping _MAP = new Mapping();
_MAP.loadMapping(_MAPPING);

InputSource xmlSource = new InputSource(new StringReader(xml));
Unmarshaller unmarshal = new Unmarshaller(_MAP);
unmarshal.setValidation(false);
Object object = unmarshal.unmarshal(xmlSource);

In the log I get this:

DEBUG - Get descriptor for: com.some.domain.ErLine found: null
DEBUG - Now in method: org.exolab.castor.xml.util.resolvers.ByIntrospection resolving: com.some.domain.ErLine
DEBUG - Ignored problem at loading class: com.some.domain.ErLine through class loader: sun.misc.Launcher$AppClassLoader@601bb1, exception: java.lang.ClassNotFoundException: com.some.domain.ErLine
DEBUG - Called addAllDescriptors with null or empty descriptor map
DEBUG - Get descriptor for: com.some.domain.ErLine found: null
DEBUG - Adding class name to missing classes: com.some.domain.ErLine
DEBUG - unable to find FieldDescriptor for 'ErLine' in ClassDescriptor of Wallet - ignoring extra element.
DEBUG - unable to find FieldDescriptor for 'ErLine' in ClassDescriptor of Wallet - ignoring extra element.
DEBUG - unable to find FieldDescriptor for 'ErLine' in ClassDescriptor of Wallet - ignoring extra element.

Ok, I think to myself, for some reason Castor can't work backwards from the <bind-xml> statement for the ErLine element to realize that <ErLine> really maps to ExpenseRequestFlexFacade (and the get/setExpenseRequestFacade) when unmarshalling... Also, the "object" being returned from unmarshal.unmarshal(..) ends up being is a Wallet, not a WalletFlexFacade!!!! So what I do is add "setErLine/getErLine" methods to WalletFlexFacade and change the <field> name attribute in the mapping from "expenseRequests" to "erLines" in hopes that Castor will notice that WalletFlexFacade is the right class to instantiate, not Wallet. Nope, that didn't work. It's just hell bent on using "Wallet" because I think it's just the first mapping it found with the proper <map-to> element.

Instead what should happen is when Castor finds two mappings with the same <map-to> xml attribute, it should inventory the differences between the two mappings and determine which mapping is more appropriate for the XML being unmarshalled (i.e. if the XML has a <ErLines> element, and the WalletFlexFacade has a mapping for that but the Wallet doesn't, it should choose the WalletFlexFacade)