JAXB marshalling XMPP stanzas

Solution 1:

How about the following?:

Create a custom XMLStreamWriter that will treat all namespace declarations as default namespaces, and then marshal to that:

ByteArrayOutputStream baos = new ByteArrayOutputStream();
XMLOutputFactory xof = XMLOutputFactory.newFactory();
XMLStreamWriter xsw = xof.createXMLStreamWriter(System.out);
xsw = new MyXMLStreamWriter(xsw);
m.marshal(iq, xsw);
xsw.close();

MyXMLStreamWriter

import java.util.Iterator;

import javax.xml.namespace.NamespaceContext;
import javax.xml.stream.XMLStreamException;
import javax.xml.stream.XMLStreamWriter;

public class MyXMLStreamWriter implements XMLStreamWriter {

    private XMLStreamWriter xsw;
    private MyNamespaceContext nc = new MyNamespaceContext();

    public MyXMLStreamWriter(XMLStreamWriter xsw) throws Exception {
        this.xsw = xsw;
        xsw.setNamespaceContext(nc);
    }

    public void close() throws XMLStreamException {
        xsw.close();
    }

    public void flush() throws XMLStreamException {
        xsw.flush();
    }

    public NamespaceContext getNamespaceContext() {
        return xsw.getNamespaceContext();
    }

    public String getPrefix(String arg0) throws XMLStreamException {
        return xsw.getPrefix(arg0);
    }

    public Object getProperty(String arg0) throws IllegalArgumentException {
        return xsw.getProperty(arg0);
    }

    public void setDefaultNamespace(String arg0) throws XMLStreamException {
        xsw.setDefaultNamespace(arg0);
    }

    public void setNamespaceContext(NamespaceContext arg0) throws XMLStreamException {
    }

    public void setPrefix(String arg0, String arg1) throws XMLStreamException {
        xsw.setPrefix(arg0, arg1);
    }

    public void writeAttribute(String arg0, String arg1) throws XMLStreamException {
        xsw.writeAttribute(arg0, arg1);
    }

    public void writeAttribute(String arg0, String arg1, String arg2) throws XMLStreamException {
        xsw.writeAttribute(arg0, arg1, arg2);
    }

    public void writeAttribute(String arg0, String arg1, String arg2, String arg3) throws XMLStreamException {
        xsw.writeAttribute(arg0, arg1, arg2, arg3);
    }

    public void writeCData(String arg0) throws XMLStreamException {
        xsw.writeCData(arg0);
    }

    public void writeCharacters(String arg0) throws XMLStreamException {
        xsw.writeCharacters(arg0);
    }

    public void writeCharacters(char[] arg0, int arg1, int arg2) throws XMLStreamException {
        xsw.writeCharacters(arg0, arg1, arg2);
    }

    public void writeComment(String arg0) throws XMLStreamException {
        xsw.writeComment(arg0);
    }

    public void writeDTD(String arg0) throws XMLStreamException {
        xsw.writeDTD(arg0);
    }

    public void writeDefaultNamespace(String arg0) throws XMLStreamException {
        xsw.writeDefaultNamespace(arg0);
    }

    public void writeEmptyElement(String arg0) throws XMLStreamException {
        xsw.writeEmptyElement(arg0);
    }

    public void writeEmptyElement(String arg0, String arg1) throws XMLStreamException {
        xsw.writeEmptyElement(arg0, arg1);
    }

    public void writeEmptyElement(String arg0, String arg1, String arg2) throws XMLStreamException {
        xsw.writeEmptyElement(arg0, arg1, arg2);
    }

    public void writeEndDocument() throws XMLStreamException {
        xsw.writeEndDocument();
    }

    public void writeEndElement() throws XMLStreamException {
        xsw.writeEndElement();
    }

    public void writeEntityRef(String arg0) throws XMLStreamException {
        xsw.writeEntityRef(arg0);
    }

    public void writeNamespace(String arg0, String arg1) throws XMLStreamException {
    }

    public void writeProcessingInstruction(String arg0) throws XMLStreamException {
        xsw.writeProcessingInstruction(arg0);
    }

    public void writeProcessingInstruction(String arg0, String arg1) throws XMLStreamException {
        xsw.writeProcessingInstruction(arg0, arg1);
    }

    public void writeStartDocument() throws XMLStreamException {
        xsw.writeStartDocument();
    }

    public void writeStartDocument(String arg0) throws XMLStreamException {
        xsw.writeStartDocument(arg0);
    }

    public void writeStartDocument(String arg0, String arg1) throws XMLStreamException {
        xsw.writeStartDocument(arg0, arg1);
    }

    public void writeStartElement(String arg0) throws XMLStreamException {
        xsw.writeStartElement(arg0);
    }

    public void writeStartElement(String arg0, String arg1) throws XMLStreamException {
        xsw.writeStartElement(arg0, arg1);
    }

    public void writeStartElement(String arg0, String arg1, String arg2) throws XMLStreamException {
        xsw.writeStartElement("", arg1, arg2);
        if(null != arg2 || arg2.length() > 0) {
            String currentDefaultNS = nc.getNamespaceURI("");
            if(!arg2.equals(currentDefaultNS)) {
                writeDefaultNamespace(arg2);
                nc.setDefaultNS(arg2);
            }
        }
     }

    private static class MyNamespaceContext implements NamespaceContext {

        private String defaultNS = "";

        public void setDefaultNS(String ns) {
            defaultNS = ns;
        }

        public String getNamespaceURI(String arg0) {
            if("".equals(arg0)) {
                return defaultNS;
            }
            return null;
        }

        public String getPrefix(String arg0) {
            return "";
        }

        public Iterator getPrefixes(String arg0) {
            return null;
        }

    }
}

Solution 2:

You can nowadays control prefixes also using a custom mapper.

    NamespacePrefixMapper namespacePrefixMapper = new com.sun.xml.bind.marshaller.NamespacePrefixMapper() {

        private Map<String, String> prefixes;

        {
            prefixes = new HashMap<>(3);
            prefixes.put(XMLConstants.XML_NS_URI, XMLConstants.XML_NS_PREFIX);
            prefixes.put(XMLConstants.W3C_XML_SCHEMA_INSTANCE_NS_URI, "xsi");
            prefixes.put(XMLConstants.W3C_XML_SCHEMA_NS_URI, "xs");
            prefixes.put(WellKnownNamespace.XML_MIME_URI, "xmime");
        }

        @Override
        public String getPreferredPrefix(String namespaceUri, String suggestion,
            boolean requirePrefix) {
            String prefix = suggestion == null ? prefixes.get(namespaceUri)
                : suggestion;
            return prefix == null ? XMLConstants.DEFAULT_NS_PREFIX : prefix;
        }

    };
    marshaller.setProperty("com.sun.xml.bind.namespacePrefixMapper",
        namespacePrefixMapper);