JAXB: example of remapping of unqualified elements

Example.java

/*
 * Add this annotation to the package:
 * @XmlSchema(xmlns = {
 * @XmlNs(prefix = "", namespaceURI = Example.NS1),
 * @XmlNs(prefix = "name2", namespaceURI = Example.NS2)}, elementFormDefault =
 * XmlNsForm.QUALIFIED)
 */
public class Example {

   @XmlType(namespace = XMLConstants.NULL_NS_URI)
   public static class Attribute {

      private String key;
      private String value;
      public Attribute(String key, String value) {
         this.key = key;
         this.value = value;
      }

      public String getKey() {
         return key;
      }

      public void setKey(String key) {
         this.key = key;
      }

      public String getValue() {
         return value;
      }

      public void setValue(String value) {
         this.value = value;
      }
   }

   @XmlRootElement(namespace = NS1)
   public static class Namespace1 {

      private List<Attribute> attributes = new ArrayList<>();

      public List<Attribute> getAttributes() {
         return attributes;
      }

      public void setAttributes(List<Attribute> attributes) {
         this.attributes = attributes;
      }

      public Namespace1 addAttribute(Attribute attribute) {
         attributes.add(attribute);
         return this;
      }
   }

   @XmlRootElement(namespace = NS2)
   public static class Namespace2 {

      private List<Attribute> attributes = new ArrayList<>();

      public List<Attribute> getAttributes() {
         return attributes;
      }

      public void setAttributes(List<Attribute> attributes) {
         this.attributes = attributes;
      }

      public Namespace2 addAttribute(Attribute attribute) {
         attributes.add(attribute);
         return this;
      }
   }

   public static final String NS1 = "namespace1";
   public static final String NS2 = "namespace2";

   public static void main(String[] arguments) throws JAXBException {
      final Namespace1 ns1 = new Namespace1().addAttribute(new Attribute("key1", "value1"));
      final Namespace2 ns2 = new Namespace2().addAttribute(new Attribute("key2", "value2"));
      serialize(ns1, true);
      serialize(ns2, true);
      serialize(ns1, false);
      serialize(ns2, false);
   }

   private static void serialize(Object obj, boolean remap) throws JAXBException {
      final XmlRootElement rootElement = obj.getClass().getAnnotation(XmlRootElement.class);
      Map<String, String> properties = null;
      if (remap && rootElement != null) {
         properties = Collections.singletonMap(JAXBRIContext.DEFAULT_NAMESPACE_REMAP, rootElement.namespace());
      }
      final JAXBContext ctx = JAXBContext.newInstance(new Class[]{obj.getClass()}, properties);
      final Marshaller marshaller = ctx.createMarshaller();
      marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
      marshaller.marshal(obj, System.out);
   }
}