Java 解析xml以获取根元素，然后在根标记下动态添加标记

我想解析xml文件以获取根元素。然后在根标记下添加名为first name的标记。我该怎么做？这就是我现在正在做的：

        DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
        DocumentBuilder db = dbf.newDocumentBuilder();            
        Document document = db.newDocument();

        Element blobKey_E = document.createElement("first-name");
        blobKey_E.appendChild( document.createTextNode( name ) );
        // NOW APPEND blobKey_E to the root element 
        // After getting the root element from the xml in some directory

        TransformerFactory tf = TransformerFactory.newInstance();
        Transformer transformer = tf.newTransformer();
        DOMSource source = new DOMSource(document);
        StreamResult result = new StreamResult(new File("/home/non-admin/NetBeansProjects/Personal Site_Testers/web/xml/xml_1.xml"));
        transformer.transform(source, result);

将

名字

附加到DOM树的末尾

插入第一个位置有点困难

Element root = document.getDocumentElement();
if (root.hasChildNodes()) {
    Node firstChild = root.getFirstChild();
    root.insertBefore(document.createElement("first-name"), firstChild);
} else {
    // Append to as per previous example
}

更新

Eleement firstName = document.createElement("first-name");
firstName.setTextContent("Henry");

root.appendChild（document.createElement（“名字”）这很好。如何在标签
名字
内插入文本？
Eleement firstName = document.createElement("first-name");
firstName.setTextContent("Henry");