Schema Imports

[adrian.brock]

Here's another test, this time imports. :-)

See: org.jboss.test.xml.ExtendedByImportUnitTestCase

I want to extend a type from another schema.
I understand that I need to rebind the type in my schema
that I want to extend, but do I really need to rebind all the other
artifacts from the schema I imported?

<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"
 targetNamespace="urn:jboss:test-extended:1.0"
 xmlns="urn:jboss:test-extended:1.0"
 xmlns:mc="urn:jboss:bean-deployer:2.0"
 elementFormDefault="qualified"
 attributeFormDefault="unqualified"
 version="1.0"
>

 <xsd:import namespace="urn:jboss:bean-deployer:2.0"/>

 <xsd:element name="extended" type="extendedType"/>

 <xsd:complexType name="extendedType">
 <xsd:complexContent>
 <xsd:extension base="mc:beanType"/>
 </xsd:complexContent>
 </xsd:complexType>

</xsd:schema>

<extended xmlns="urn:jboss:test-extended:1.0"
 xmlns:mc="urn:jboss:bean-deployer:2.0"
 name="TestAspect" class="TestClass">
 <mc:property name="testProperty">testString</mc:property>
</extended>

If I add the binding for the property to my schema
(the commented code) it works,
but shouldn't it be using the schema bindings from the imported
schema? Rather than forcing me to rebind everything in mine?

public class ExtendedSchemaInitializer implements SchemaBindingInitializer
{
 /** The namespace */
 public static final String EXTENDED_NS = "urn:jboss:test-extended:1.0";

 /** The extended binding */
 private static final QName extendedTypeQName = new QName(EXTENDED_NS, "extendedType");

 public SchemaBinding init(SchemaBinding schema)
 {
 // extended binding
 TypeBinding extendedType = schema.getType(extendedTypeQName);
 BeanSchemaBindingHelper.initBeanHandlers(extendedType);
 extendedType.setHandler(new BeanHandler()
 {
 public Object startElement(Object parent, QName name, ElementBinding element)
 {
 return new Extended();
 }
 });

 /*
 TypeBinding propertyType = schema.getType(BeanSchemaBinding20.propertyTypeQName);
 BeanSchemaBindingHelper.initPropertyHandlers(propertyType);
 */

 return schema;
 }
}

[adrian.brock]

Actually, even the commented out code doesn't work properly.
It is invoking the endElement() of the interceptor rather than the add()

[adrian.brock]

Ignore that last comment. It was my test that was broken :-)

[aloubyansky]

The way it currently works, schema import/include are handled by Xerces. When Xerces parses an XSD it creates an instance of XSModel (Xerces' schema API) and imports/includes other XSDs into the XSModel instance. JBossXB/XsdBinder works with the resulting XSModel instance. So, it's not like we import/include one JBossXB SchemaBinding into another one as you would expect.

But I agree with your expection. There is an initializer registered for the imported schema that should be run before the initializer of the importing schema.

[aloubyansky]

But actually it still would not be the same as importing one SchemaBinding into another one since imported schemas are re-parsed/re-bound.

[adrian.brock]

Why doesn't it just resolve the schema binding based on the namespace?

In this case, when it hits mc:property it delegates to the schema binding
for "urn:jboss:bean-deployer:2.0"

This is the way I had it working in my prototype:

 public ElementBinding AbstractSchemaBinding::resolveElement(QName name)
 {
 if (name == null)
 throw new IllegalArgumentException("Null name");

 ParticleBinding binding = (ParticleBinding) elementsByName.get(name);
 // Not a local name
 if (binding == null)
 {
...
 // Use the resolver to get the element if it is not the current namespace
 String uri = name.getNamespaceURI();
 if (uri.equals(targetNamespace) == false)
 {
 String schemaLocation = null; // @todo schemaLocation 4
 SchemaBinding schema = AbstractSchemaBindingResolver.resolveSchemaBinding(true, null, schemaBindingResolver, uri, null, schemaLocation);
 return schema.resolveElement(name);
 }
 // @todo exception element not installed
 throw new IllegalStateException("Element not installed " + name);
 }
 return (ElementBinding) binding.getTerm();
 }

[aloubyansky]

It does so when it has to resolve a wildcard content element. But import/include are not done by JBossXB.

[adrian.brock]

Yes, but couldn't JBossXB weed out the foreign namespace
then do a similar thing as the wildcard process for it?

[aloubyansky]

It's an alternative.

What if SchemaBindingResolver is not provided?
I guess, one could be created internally.

What if schema initializer associated with the importing schema wants to customize bindings for the imported schema?
Probably, it would have to clone the component to be customized with all its children and copy into the importing schema. This doesn't look nice.

[adrian.brock]

Wouldn't customising the bindings locally
be the exception rather than the rule?

Normally, you would do like I did.
i.e. extend the base type and initialize it locally
but it is still likely to reference particles from the other binding
which you don't want to redo yourself.

[aloubyansky]

I don't know what would be an exception at this moment.

I am not saying you should redo referenced bindings yourself. To fix this we have at least two alternatives to choose from.

An advantage I can see in your suggestion is that if we look at SchemaBindingResolver as a library of SchemaBindings then it probably should not contain multiple versions of the same schemas (in different SchemaBinding instances). Or maybe it's ok... :)

[aloubyansky]

The issue for this

xsd:import and schema binding initializer
http://jira.jboss.com/jira/browse/JBXB-60