JAXB SchemaFactory source order must follow import

Question

Using latest JAXB (Sun) and have a hierarchy of schemas that use import directives between schemas to share type definitions. Schema validation is activated on the setSchema call to Marshaller/Unmarshaller in JAXB which should defer validation to Xerces (using Java 1.5). I don't want to know the order of import directives between schemas when creating the Schema object with SchemaFactory. Unfortunately, I haven't found a Xerces feature/property that allows for this. For example, if a.xsd is pulled into b.xsd with an import then the following code doesn't work:

FileInputStream a = new FileInputStream("a.xsd");
FileInputStream b = new FileInputStream("b.xsd");

Schema schema = SchemaFactory.newInstance(
   XMLConstants.W3C_XML_SCHEMA_NS_URI).newSchema(
      new Source[] { 
          new StreamSource(b),
          new StreamSource(a) 
      }
   );

The order of the Source array has to be a.xsd then b.xsd. Any way around this?

Answer 1

What if you create a schema on the root Source, and then set a ResourceResolver (LSResourceResolver) to resolve the other imported schemas during the schema creation.

Answer 2

Late post of the code.

Generate a validation Schema with:

SchemaFactory factory = SchemaFactory
.newInstance(XMLConstants.W3C_XML_SCHEMA_NS_URI);
factory.setResourceResolver(new SimpleResolver(streams));
....
Schema schemaGrammers = factory.newSchema(streams.toArray(new SchemaSource[0]));

The Schema (schemaGrammers object) gets injected into the Marshaller:

Marshaller m = ...createMarshaller();
m.setSchema(<schemaGrammers>);

And the SimpleResolver implements the LSResourceResolver class:

private class SimpleResolver implements LSResourceResolver {

    private Set<Source> streams;

    public SimpleResolver(Set<Source> streams) {
        this.streams = streams;
    }

    @Override
    public LSInput resolveResource(String type, String namespaceURI,
            String publicId, String systemId, String baseURI) {
        DOMImplementationRegistry registry;
        try {

            registry = DOMImplementationRegistry.newInstance();
            DOMImplementationLS domImplementationLS = (DOMImplementationLS) registry
                    .getDOMImplementation("LS 3.0");

            LSInput ret = domImplementationLS.createLSInput();

            for (Source source : streams) {
                SchemaSource schema = (SchemaSource) source;
                if (schema.getResourceName().equals(
                        schema.getResourceName(systemId))
                        & schema.getTargetNamespace().equals(namespaceURI)) {
                    logger.debug(
                            "Resolved systemid [{}] with namespace [{}]",
                            schema.getResourceName(systemId), namespaceURI);

                    URL url = new URL(schema.getSystemId());
                    URLConnection uc = url.openConnection();

                    ret.setByteStream(uc.getInputStream());
                    ret.setSystemId(systemId);
                    return ret;
                }
            }

        } catch (ClassCastException e) {
            logger.error(e.getMessage());
        } catch (ClassNotFoundException e) {
            logger.error(e.getMessage());
        } catch (InstantiationException e) {
            logger.error(e.getMessage());
        } catch (IllegalAccessException e) {
            logger.error(e.getMessage());
        } catch (FileNotFoundException e) {
            logger.error(e.getMessage());
        } catch (IOException e) {
            logger.error(e.getMessage());
        }

        logger.error("No stream found for system id [{}]", systemId);
        return null;
    }

}

A new input stream has to be created otherwise a conflict occurs. Not sure why (didn't bother to debug the code) but the streams I pass to the constructor [ie. the Set object] have already been read.