如何正确读取XML文件中的节点值？

Question

I have a problem when I try to retrieve an XML Node Value. It will be hard to ask this question without a bit of explanation. I have a Server - Client Chatroom I have created, and the Server Handles all of the XML Data which contains the User's usernames. For example the user sends a message that will be broadcasted to everyone on the server. When the message arrives at the server the server will check an array based on the users current IP address. If the IP is in the array another array with a corresponding number will return the username which is then broadcasted to all of the chatroom users. My problem surfaces when a new user or an offline user joins the server. If the IP is not in the array the server checks an XML file that has all of the online or old users last known IP (This part is getting resolved for the old users who have new IPs) and the server will then add it to the array. This works out in theory however in code it doesn't produce the same results. I am able to add the Current IP to the array but I can not get the username. And I believe it is due to the fact that the user's old IP is the node name and the username is the node value. For Example: Usernames.xml File

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<Server>
    <i0000>User</i0000>
    <i1921681114>Chappy</i1921681114>
</Server>

The function that should add it to the array:

public static void addInArray(String IPtoCheck) throws Exception{
        File fXmlFile = new File("Usernames.xml");
        DocumentBuilderFactory dbFactory = DocumentBuilderFactory.newInstance();
        DocumentBuilder dBuilder = dbFactory.newDocumentBuilder();
        Document doc = dBuilder.parse(fXmlFile);

        doc.getDocumentElement().normalize();
        NodeList nList = doc.getElementsByTagName(IPtoCheck);
        for(int i=0; nList.getLength()>i; i++){
            Node nNode = nList.item(i);
            if (nNode.getNodeType() == Node.ELEMENT_NODE) {
                Element eElement = (Element) nNode;
                if(eElement.getNodeName().equals(IPtoCheck)){
                    int used = 0;
                    while (used < 63){
                        if(IPs[used].equals("no")){
                            IPs[used] = IPtoCheck;
                            usernames[used] = eElement.getNodeValue();
                            AppendArea.Apen(3, usernames[used]);
                            break;
                        }
                        used++;
                    }
                }
            }
        }
    }

Also I should add that i did use

Arrays.fill(IPs, "no");
Arrays.fill(usernames, "no");

no represents an open array spot

Also the IPtoCheck String is a modified IP value. For example in the XML file the ip node is:

i1921681114

this is actually 192.168.1.114

After all this lengthy explanation my question is as follows:

How do I properly read a Node Value in an XML file with Java?

because the eElement.getNodeValue(); isn't returning the correct value it only returns 'null'

Answer 1

The org.w3c.dom.Element object never has a node value, so it will always return null.

You need to get its children. If you use:

eElement.getFirstChild().getNodeValue();

You will retrieve the first child node of your element, which is the text node you want.

You can also use:

eElement.getFirstChild().getTextContent();

which returns the text content of the element, which, in this case, has the same result.

If you find the DOM API in Java counterintuitive, you can use other APIs, such as JDOM or DOM4J, or use other J2SE standard methods such as XPath.