Java xml parse getElementById returns null

So for some reason when parsing XML in java I can't getElementById("ID_VALUE") however this all works fine within android, but not with regular java. When I attempt to parse the XML I just get null for the element. I've seen a couple thoughts on maybe using a schema, however I have no idea how to do that.

Java

public void getFromID()throws Exception {
File file = new File("/home/nodes.xml");
DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
//factory.setValidating(true);
DocumentBuilder builder = factory.newDocumentBuilder();
Document document = builder.parse(file);
//document.getDocumentElement().normalize();
System.out.println(id);
Element element = document.getElementById(id);
System.out.println(element);
//Element element = (Element) document.getElementsByTagName("node").item(0);
//System.out.println(element.getNodeValue());
this.address = element.getAttribute("address");
this.port = Integer.parseInt(element.getAttribute("port"));
this.base64Key = element.getAttribute("key");
System.out.println(address);
System.out.println(port);
System.out.println(base64Key);
}
public void save()throws Exception {
File file = new File("/home/nodes.xml");
DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
//factory.setValidating(true);
DocumentBuilder builder = factory.newDocumentBuilder();
Document document = builder.newDocument();
Element root = document.createElement("nodes");
Element enode = document.createElement("node");
enode.setAttribute("id", id);
enode.setAttribute("address", address);
enode.setAttribute("port", port+"");
enode.setAttribute("key", base64Key);
//enode.setIdAttributeNS(null, "id", true);
enode.setIdAttribute("id", true);
root.appendChild(enode);
document.appendChild(root);
//document.getDocumentElement().normalize();
document.setXmlStandalone(true);
Transformer tfactory = TransformerFactory.newInstance().newTransformer();
tfactory.setOutputProperty(OutputKeys.METHOD, "xml");
tfactory.setOutputProperty(OutputKeys.ENCODING, "UTF-8");
tfactory.transform(new DOMSource(document), new StreamResult(new FileOutputStream(file)));
}

XML

<?xml version="1.0" encoding="UTF-8"?><nodes><node address="127.0.0.1" id="123123" key="ASDASDASD" port="8000"/></nodes>

Since you know the structure of your XML file, I suggest you to use JAXB (JAva Xml Binding) API in order not to parse raw XML but rather map the XML file to a POJO you have predefined.

Add the dependency to your pom.xml:

<dependency>
<groupId>javax.xml.bind</groupId>
<artifactId>jaxb-api</artifactId>
<version>2.3.0</version>
</dependency>

Then, create your POJO classes (let's say Nodes.java and Node.java) and annotate the fields according to your XML file.

@XmlRootElement(name = "nodes")
public class Nodes {
@XmlElement(name = "node")
private Node node;            
public Node getNode() {
return node; 
}
}

public class Node {
@XmlAttribute(name="address")
private String address;
@XmlAttribute(name="id")
private String id;
@XmlAttribute(name="key")
private String key;
@XmlAttribute(name="port")
private String port;
public String getAddress() {return address;}
public String getId() {return id;}
public String getKey() {return key;}
public String getPort() {return port;}
}

Hence, parse the XML file against your class using the JAXB Unmarshaller (note: here I assume the XML file is loaded into a String xmlString):

jaxbContext = JAXBContext.newInstance(Nodes.class);              
Unmarshaller jaxbUnmarshaller = jaxbContext.createUnmarshaller();
Nodes nodes = (Nodes) jaxbUnmarshaller.unmarshal(new StringReader(xmlString)); 

At this point, your whole XML is loaded into the instance Nodes nodes so you can just do nodes.getNode().getId() to retrieve your value (as well as all the other values).

General note: you should use the general Xml parser just when you really don't know how the XML file is done and you need to explore it. If you know the XML (i.e. you know what object it represents), then it's better to represent it as such.