Link XML and XSD using java

i'm trying to write the header for an xml file so it would be something like this:

<file xmlns="http://my_namespace"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://my_namespace file.xsd">

however, I can't seem to find how to do it using the Document class in java. This is what I have:

public void exportToXML() {
        DocumentBuilderFactory dbFactory = DocumentBuilderFactory.newInstance();
        DocumentBuilder dBuilder;

        try {

            dBuilder = dbFactory.newDocumentBuilder();
            Document doc = dBuilder.newDocument();
            doc.setXmlStandalone(true);
            doc.createTextNode("<file xmlns=\"http://my_namespace"\n" +
                    "xmlns:xsi=\"http://www.w3.org/2001/XMLSchema-instance\"\n" +
                    "xsi:schemaLocation=\"http://my_namespace file.xsd\">");
            Element mainRootElement = doc.createElement("MainRootElement");
            doc.appendChild(mainRootElement);

            for(int i = 0; i < tipoDadosParaExportar.length; i++) {
                mainRootElement.appendChild(criarFilhos(doc, tipoDadosParaExportar[i]));
            }
            Transformer tr = TransformerFactory.newInstance().newTransformer();
            tr.transform(new DOMSource(doc),
                    new StreamResult(new FileOutputStream(filename)));

        } catch (Exception e) {
            e.printStackTrace();
        }
    }

I tried writing it on the file using the createTextNode but it didn't work either, it only writes the version before showing the elements.

PrintStartXMLFile

Would appreciate if you could help me. Have a nice day

Your createTextNode() method is only suitable for creating text nodes, it's not suitable for creating elements. You need to use createElement() for this. If you're doing this by building a tree, then you need to build nodes, you can't write lexical markup.

I'm not sure what MainRootElement is supposed to be; you've only given a fragment of your desired output so it's hard to tell.

Creating a DOM tree and then serializing it is a pretty laborious way of constructing an XML file. Using something like an XMLEventWriter is easier. But to be honest, I got frustrated by all the existing approaches and wrote a new library for the purpose as part of Saxon 10. It's called simply "Push", and looks something like this:

Processor proc = new Processor();
Serializer serializer = proc.newSerializer(new File(fileName));
Push push = proc.newPush(serializer);
Document doc = push.document(true);
doc.setDefaultNamespace("http://my_namespace");
Element root = doc.element("root")
  .attribute(new QName("xsi", "http://www.w3.org/2001/XMLSchema-instance", "schemaLocation"), 
             "http://my_namespace file.xsd");
doc.close();