DocumentBuilder doc (with root element) outputs null even though root element is appended

Question

I'm attempting to have it return my empty root element with attributes but am getting [#document: null] output. Am I absolutely required to have a child element for the root?

String docDate = "1";
String docNumber = "1";
String orderType = "1";
String transactionType = "1";

try {
    DocumentBuilderFactory docFactory = DocumentBuilderFactory.newInstance();
    DocumentBuilder docBuilder = docFactory.newDocumentBuilder();

    Document doc = docBuilder.newDocument();

    Element rootElement = doc.createElement("InvoiceRequest");

    Attr attr = doc.createAttribute("documentDate");
    attr.setValue(docDate);
    rootElement.setAttributeNode(attr);

    Attr attr2 = doc.createAttribute("documentNumber");
    attr2.setValue(docNumber);
    rootElement.setAttributeNode(attr2);

    Attr attr3 = doc.createAttribute("orderType");
    attr3.setValue(orderType);
    rootElement.setAttributeNode(attr3);

    Attr attr4 = doc.createAttribute("transactionType");
    attr4.setValue(transactionType);
    rootElement.setAttributeNode(attr4);

    doc.appendChild(rootElement);
    System.out.println("doc: " + doc.toString());
} catch (Exception e) { 
    e.printStackTrace();
}

Answer 1

DocumentImpl is a subclass of NodeImpl , whose toString() implementation reads:

public String toString() {
    return "["+getNodeName()+": "+getNodeValue()+"]";
}

getNodeName() returns #document (which makes sense) - this is defined in CoreDocumentImpl . getNodeValue() returns null because it is not overridden. This behaviour is even mentioned in the Node documentation:

In cases where there is no obvious mapping of these attributes for a specific nodeType (eg, nodeValue for an Element or attributes for a Comment ), this returns null.

Because your root element is not included in either getNodeName() or getNodeValue() , it might look empty. But there's nothing to worry about. You need other methods to render the document as an XML string.

Answer 2

The toString() method which you are using here is doing nothing but just returning:-

"["+getNodeName()+": "+getNodeValue()+"]"

so correspondingly you are getting :-

[#document: null] //nodeName as document and null nodevalue

Don't worry about it & keep on doing your further processing, you will get your intended result and not an NPE .