Java DOM XML is skipping xmlns properties

问题

I need to generate an xml file in Java, so I chose to use DOM (until there everything is ok), here is the root tag of what i need to create

<?xml version="1.0" encoding="utf-8"?>
<KeyContainer Version="1.0" xmlns="urn:ietf:params:xml:ns:keyprov:pskc:1.0" xmlns:ds="http://www.w3.org/2000/09/xmldsig#" xmlns:xenc="http://www.w3.org/2001/04/xmlenc#" xmlns:xml="http://www.w3.org/XML/1998/namespace">

Here is my source code

PrintWriter out = new PrintWriter(path);
Document xmldoc = null;
DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
        DocumentBuilder builder = factory.newDocumentBuilder();
        DOMImplementation impl = builder.getDOMImplementation();
        Element e = null;
        Node n = null;
        xmldoc = impl.createDocument(null, "KeyContainer", null);
        /* Noeuds non bouclés */
        Element keycontainer = xmldoc.getDocumentElement();
            keycontainer.setAttributeNS(null, "Version", "1.0");
            keycontainer.setAttributeNS("http://www.w3.org/2000/xmlns/", "xmlns:ds","http://www.w3.org/2000/09/xmldsig#");
            keycontainer.setAttributeNS("http://www.w3.org/2000/xmlns/", "xmlns:xenc", "http://www.w3.org/2001/04/xmlenc#");
            keycontainer.setAttributeNS("http://www.w3.org/2000/xmlns/", "xmlns:xml", "http://www.w3.org/XML/1998/namespace");
            keycontainer.setAttributeNS("http://www.w3.org/2000/xmlns/", "xmlns", "urn:ietf:params:xml:ns:keyprov:pskc:1.0");
/* Non relevant Info*/
DOMSource domSource = new DOMSource(xmldoc);
        StreamResult streamResult = new StreamResult(out);
        TransformerFactory tf = TransformerFactory.newInstance();
        Transformer serializer = tf.newTransformer();
        serializer.setOutputProperty(OutputKeys.ENCODING,"utf-8");
        serializer.setOutputProperty(OutputKeys.VERSION,"1.0");
        serializer.setOutputProperty(OutputKeys.INDENT,"yes");
        serializer.setOutputProperty(OutputKeys.STANDALONE,"yes");
        serializer.transform(domSource, streamResult); 

And here is what I get

<?xml version="1.0" encoding="utf-8" standalone="no"?>
<KeyContainer xmlns="" xmlns:ds="http://www.w3.org/2000/09/xmldsig#" xmlns:xenc="http://www.w3.org/2001/04/xmlenc#" Version="1.0">

Problem is the xmlns property is empty, and xmlns:xml is missing, what can I do to get all information ?

Thanks a lot stackoverflow

(PS : Got NAMESPACE_ERR if anything else than "http://www.w3.org/2000/xmlns/" in NamespaceURI field)

回答1:

Two things are required to get rid of xmlns=""

Create the Document with the desired namespace URI as such:

xmldoc = impl.createDocument("urn:ietf:params:xml:ns:keyprov:pskc:1.0", "KeyContainer", null);

Remove the following line as it is now unnecessary:

keycontainer.setAttributeNS("http://www.w3.org/2000/xmlns/", "xmlns", "urn:ietf:params:xml:ns:keyprov:pskc:1.0");

Regarding the xmlns:xml attribute, the API is silently dropping it. See line 173 of NamespaceMappings. A bit of research turns up that the behavior of declaring that particular namespace is undefined and is not recommended.

回答2:

To make DOM namespace aware, do not forget to enable it in the documentbuilderfactory using the setNamespaceAware method.

来源：https://stackoverflow.com/questions/1294981/java-dom-xml-is-skipping-xmlns-properties