Java XML How to - Use xpath to find and add/replace more children to a Nodelist in an XML file

I have an xml file (ToThis.xml) that i am updating with array variables. Am using Xpath to update to this xml file but i can only update the first array element. see below .

xml file (ToThis.xml) what i get

<?xml version="1.0" encoding="UTF-8"?><map xmlns="http://www.w3.org/2005/xpath-functions">
<string key="ankomstDato">2020-08-20</string>
<array key="planlagtAntallPerUndergruppe">
<map>
<number key="antall">67</number>
<string key="kode">SLAKTEGRIS</string>
</map> 
</array>   
</map>

xml file that i would like to get should be like this below

<?xml version="1.0" encoding="UTF-8"?><map xmlns="http://www.w3.org/2005/xpath-functions">
<string key="ankomstDato">2020-08-20</string>
<array key="planlagtAntallPerUndergruppe">
<map>
<number key="antall">67</number>
<string key="kode">SLAKTEGRIS</string>
</map> 
<map>
<number key="antall">4</number>
<string key="kode">UNGSAU</string>
</map>
</array>   
</map>

Below is portion of the code where it get me the first result. NOTE( The two array variable in real scenario are not hard coded they are assigned dynamically)

public void Write2XMLfile(){
XPathFactory xpathFact = XPathFactory.newInstance();
XPath xpath = xpathFact.newXPath();
try {
//
String filepath = "E:/utils/Tothis.xml";
//
DocumentBuilderFactory docFactory = DocumentBuilderFactory.newInstance();
DocumentBuilder docBuilder = docFactory.newDocumentBuilder();
Document doc = docBuilder.parse(filepath);
planlagtAntallPerUndergruppe_antall_value[0] = "67";                
planlagtAntallPerUndergruppe_kode_value[0] = "SLAKTEGRIS";
planlagtAntallPerUndergruppe_antall_value[1] = "4";                
planlagtAntallPerUndergruppe_kode_value[1] = "UNGSAU";        
//2.  planlagtAntallPerUndergruppe **************************
System.out.println("\n This is second" );
Node planlagtAntallPerUndergruppe = (Node) xpath.evaluate("/map/array[@key='planlagtAntallPerUndergruppe']/*", doc, XPathConstants.NODE);
if(null != planlagtAntallPerUndergruppe) {
NodeList nodeList = planlagtAntallPerUndergruppe.getChildNodes();
for (int i = 0;null!=nodeList && i < nodeList.getLength(); i++) {
Node nod = nodeList.item(i);
if(nod.getNodeType() == Node.ELEMENT_NODE){
NodeList arrayElements_18 = (NodeList) xpath.evaluate("/map/array[@key='planlagtAntallPerUndergruppe']/*", doc, XPathConstants.NODESET);
//System.out.println("\n number of elements" + arrayElements_18.getLength());
for (int j = 0; j < arrayElements_18.getLength(); j++) {
//.  antall
Node antall = (Node) xpath.evaluate("(/map/array/map/number[@key='antall'])[1]", doc, XPathConstants.NODE);
antall.setTextContent(planlagtAntallPerUndergruppe_antall_value[j]);
// end antall
//.  kode
Node kode = (Node) xpath.evaluate("(/map/array/map/string[@key='kode'])[1]", doc, XPathConstants.NODE);
kode.setTextContent(planlagtAntallPerUndergruppe_kode_value[j]);
//System.out.println("\n\n antall: " + planlagtAntallPerUndergruppe_antall_value[j]);
// end kode                       
}                    
}
}
}
// end array planlagtAntallPerUndergruppe
// write the content into xml file
TransformerFactory transformerFactory = TransformerFactory.newInstance();
Transformer transformer = transformerFactory.newTransformer();
DOMSource source = new DOMSource(doc);
StreamResult result = new StreamResult(new File(filepath));
transformer.transform(source, result);
System.out.println("Done Updating The Api_XML_Format.xml");
} catch (ParserConfigurationException pce) {
pce.printStackTrace();
} catch (TransformerException tfe) {
tfe.printStackTrace();
} catch (IOException ioe) {
ioe.printStackTrace();
} catch (SAXException sae) {
sae.printStackTrace();
} catch (XPathExpressionException xee) {
xee.printStackTrace();
}
}

Xpath is purposely used to trace/read through an xml but cannot be used to modify an xml.

So, I changed my code from using XPath to using DOM Parser.

try
{
DocumentBuilderFactory docFactory = DocumentBuilderFactory.newInstance();
DocumentBuilder docBuilder = docFactory.newDocumentBuilder();
Document doc = docBuilder.newDocument();
// Map root element
Element rootElement = doc.createElement("map");
doc.appendChild(rootElement);
//ROOT map
//1. ankomstDato
Element ankomstDato = doc.createElement("string");
Attr attrType_ankomstDato = doc.createAttribute("key");
attrType_ankomstDato.setValue("ankomstDato");
ankomstDato.setAttributeNode(attrType_ankomstDato);
ankomstDato.appendChild(doc.createTextNode(ankomstDato_value));
rootElement.appendChild(ankomstDato);
//. planlagtAntallPerUndergruppe
// planlagtAntallPerUndergruppe element
if (planlagtAntallPerUndergruppe_Count !=0){
Element planlagtAntallPerUndergruppe = doc.createElement("array");
rootElement.appendChild(planlagtAntallPerUndergruppe);
Attr attr = doc.createAttribute("key");
attr.setValue("planlagtAntallPerUndergruppe");
planlagtAntallPerUndergruppe.setAttributeNode(attr);
for (int i = 0; i < planlagtAntallPerUndergruppe_Count; i ++){
//to add "map" element
Element map1 = doc.createElement("map");
planlagtAntallPerUndergruppe.appendChild(map1);
// antall element
Element antall = doc.createElement("number");
Attr attrType = doc.createAttribute("key");
attrType.setValue("antall");
antall.setAttributeNode(attrType);
antall.appendChild(doc.createTextNode(planlagtAntallPerUndergruppe_antall_value[i]));
map1.appendChild(antall);
//kode element
Element kode = doc.createElement("string");
Attr attrType1 = doc.createAttribute("key");
attrType1.setValue("kode");
kode.setAttributeNode(attrType1);
kode.appendChild(doc.createTextNode(planlagtAntallPerUndergruppe_kode_value[i]));
map1.appendChild(kode);
}
}
//end planlagtAntallPerUndergruppe
// Write the content into XML file
DOMSource source = new DOMSource(doc);
StreamResult result = new StreamResult(new File("E:/utils/students-new.xml"));
TransformerFactory transformerFactory = TransformerFactory.newInstance();
Transformer transformer = transformerFactory.newTransformer();
// Beautify the format of the resulted XML
transformer.setOutputProperty(OutputKeys.INDENT, "yes");
transformer.setOutputProperty("{http://xml.apache.org/xslt}indent-amount", "4");
transformer.transform(source, result);
}
catch(Exception ex)
{
ex.printStackTrace();
}
}

pass collected arrays into Write2XMLfile method as parameters

public void Write2XMLfile(String[] planlagtAntallPerUndergruppe_antall_value, String[] planlagtAntallPerUndergruppe_kode_value) {
try {
DocumentBuilderFactory dbFactory = DocumentBuilderFactory.newInstance();
DocumentBuilder dBuilder = dbFactory.newDocumentBuilder();
Document doc = dBuilder.newDocument();
Element rootElement = doc.createElement("map");
doc.appendChild(rootElement);
Element mainString = doc.createElement("string");
mainString.setAttribute("key", "ankomstDato");
rootElement.appendChild(mainString).setTextContent("2020-08-20");
Element array = doc.createElement("array");
array.setAttribute("key", "planlagtAntallPerUndergruppe");
rootElement.appendChild(array);
if(planlagtAntallPerUndergruppe_antall_value.length>0){
for (int i = 0; i < planlagtAntallPerUndergruppe_antall_value.length; i++) {
Element map = doc.createElement("map");
array.appendChild(map);
Element number =  doc.createElement("number");
number.setAttribute("key", "antall");
map.appendChild(number).setTextContent(planlagtAntallPerUndergruppe_antall_value[i]);
Element string =  doc.createElement("string");
string.setAttribute("key", "kode");
map.appendChild(string).setTextContent(planlagtAntallPerUndergruppe_kode_value[i]);
}
}
TransformerFactory transformerFactory = TransformerFactory.newInstance();
Transformer transformer = transformerFactory.newTransformer();
transformer.setOutputProperty(OutputKeys.INDENT, "yes");
transformer.setOutputProperty("{http://xml.apache.org/xslt}indent-amount", "2");
DOMSource source = new DOMSource(doc);
StreamResult output = new StreamResult(new File("output.xml"));
transformer.transform(source, output);
} catch (Exception e) {
e.printStackTrace();
}
}

output.xml

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<map>
<string key="ankomstDato">2020-08-20</string>
<array key="planlagtAntallPerUndergruppe">
<map>
<number key="antall">67</number>
<string key="kode">SLAKTEGRIS</string>
</map>
<map>
<number key="antall">4</number>
<string key="kode">UNGSAU</string>
</map>
</array>
</map>