Unmarshalling and validating xml without a namespace using JAXB

Unmarshalling and validating xml using jaxb where the xml does not have a namespace specified has driven me crazy for years now. I even did text insertion on the xml before unmarshalling as a workaround. Here's a good way of doing it that's great for xml without any namespace attributes (on the child elements too):

This code unmarshals the object into an org.jdom.Document object then recurses through the object setting namespaces. That object is then passed as a Source to the unmarshaller.

Note also that I did not have @XmlRootElement annotation on GCOM3DRequest so I asked the unmarshaller to unmarshal to that class explicitly.

Primary source for this was here.

package au.gov.amsa.er.nwm.scenario;

import java.io.IOException;
import java.io.InputStream;

import javax.xml.XMLConstants;
import javax.xml.bind.JAXBContext;
import javax.xml.bind.JAXBElement;
import javax.xml.bind.JAXBException;
import javax.xml.bind.Marshaller;
import javax.xml.bind.Unmarshaller;
import javax.xml.transform.Source;
import javax.xml.validation.Schema;
import javax.xml.validation.SchemaFactory;

import org.apache.log4j.Logger;
import org.jdom.Element;
import org.jdom.JDOMException;
import org.jdom.Namespace;
import org.jdom.input.SAXBuilder;
import org.jdom.transform.JDOMSource;
import org.xml.sax.SAXException;

import au.gov.amsa.nwm.gcom3drequest.GCOM3DRequest;
import au.gov.amsa.nwm.gcom3drequest.ObjectFactory;

public class RequestMarshaller {

 private static Logger log = Logger.getLogger(RequestMarshaller.class);
 private JAXBContext jc;
 private Schema schema;

 public RequestMarshaller() {
  try {
   jc = JAXBContext.newInstance(ObjectFactory.class.getPackage()
     .getName());
  } catch (JAXBException e) {
   throw new RuntimeException(e);
  }

  loadSchema();

 }

 private void loadSchema() {
  SchemaFactory sf = SchemaFactory
    .newInstance(XMLConstants.W3C_XML_SCHEMA_NS_URI);
  try {
   schema = sf.newSchema(getClass().getResource(
     "request/gcom3dRequest.xsd"));
  } catch (SAXException e) {
   throw new RuntimeException(e);
  }
 }

 private Unmarshaller createUnmarshaller() {
  Unmarshaller u;
  try {
   u = jc.createUnmarshaller();
   // validate against the schema
   u.setSchema(schema);
   return u;
  } catch (JAXBException e) {
   throw new RuntimeException(e);
  }
 }

 private static Namespace DEFAULT_NS = Namespace
   .getNamespace("http://www.amsa.gov.au/nwm/gcom3dRequest");

 public GCOM3DRequest unmarshal(InputStream is) throws JAXBException {

  try {
   SAXBuilder sb = new SAXBuilder(false);
   org.jdom.Document doc = sb.build(is);
   setNamespace(doc.getRootElement(), DEFAULT_NS, true);

   Source src = new JDOMSource(doc);
   Unmarshaller u = createUnmarshaller();
   u.setSchema(schema);
   JAXBElement element = u.unmarshal(src,
     GCOM3DRequest.class);
   GCOM3DRequest gcom3d = element.getValue();
   return gcom3d;
  } catch (IOException e) {
         throw new RuntimeException(e);
        } catch (JDOMException e) {
            throw new RuntimeException(e);
        }
    }

    private static void setNamespace(Element elem, Namespace ns, boolean recurse) {
        elem.setNamespace(ns);
        if (recurse) {
            for (Object o : elem.getChildren()) {
                setNamespace((Element) o, ns, recurse);
            }
        }
    }

    public Marshaller createMarshaller() {
        Marshaller m;
        try {
            m = jc.createMarshaller();
            m.setSchema(schema);
            return m;
        } catch (JAXBException e) {
            throw new RuntimeException(e);
        }
    }

}