java - Loop through all elements in XML using NodeList

Question

I want to loop through all elements in a piece of XML printing each one. My problem is that I keep getting a null pointer exception after the staff1 tag, i.e. john 465456433 gmail1 area1 city1

This my Java code to print all elements in an xml file:

File fXmlFile = new File("file.xml");
DocumentBuilderFactory dbFactory = DocumentBuilderFactory.newInstance();
DocumentBuilder dBuilder = dbFactory.newDocumentBuilder();
Document doc = dBuilder.parse(fXmlFile);

doc.getDocumentElement().normalize();

System.out.println("Root element :" + doc.getDocumentElement().getNodeName());

NodeList nList = doc.getElementsByTagName("*");

System.out.println("----------------------------");

Node n=null;
Element eElement=null;

for (int i = 0; i < nList.getLength(); i++) {           
  System.out.println(nList.getLength());     
  n= nList.item(i);                            
  System.out.println("
Current Element :" + n.getNodeName());


  if (n.getNodeType() == Node.ELEMENT_NODE) {
    eElement = (Element) n.getChildNodes();
    System.out.println("
Current Element :" + n.getNodeName());
    name = eElement.getElementsByTagName("name").item(i).getTextContent(); //here throws null pointer exception after printing staff1 tag
    phone = eElement.getElementsByTagName("phone").item(i).getTextContent();
    email = eElement.getElementsByTagName("email").item(i).getTextContent();
    area = eElement.getElementsByTagName("area").item(i).getTextContent();
    city = eElement.getElementsByTagName("city").item(i).getTextContent();
  }
  n.getNextSibling();
}

XML File:

<?xml version="1.0"?>
<company>
  <staff1>
    <name>john</name>
    <phone>465456433</phone>
    <email>gmail1</email>
    <area>area1</area>
    <city>city1</city>
  </staff1>
  <staff2>
    <name>mary</name>
    <phone>4655556433</phone>
    <email>gmail2</email>
    <area>area2</area>
    <city>city2</city>
  </staff2>
  <staff3>
    <name>furvi</name>
    <phone>4655433</phone>
    <email>gmail3</email>
    <area>area3</area>
    <city>city3</city>
  </staff3>
</company>

Expected Output:

john
465456433
gmail1
area1
city1
mary
4655556433
gmail2
area2
city2
furvi
4655433
gmail3
area3
city3

Answer 1

    DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
    DocumentBuilder db = dbf.newDocumentBuilder();
    Document dom = db.parse("file.xml");
    Element docEle = dom.getDocumentElement();
    NodeList nl = docEle.getChildNodes();
    int length = nl.getLength();
    for (int i = 0; i < length; i++) {
        if (nl.item(i).getNodeType() == Node.ELEMENT_NODE) {
            Element el = (Element) nl.item(i);
            if (el.getNodeName().contains("staff")) {
                String name = el.getElementsByTagName("name").item(0).getTextContent();
                String phone = el.getElementsByTagName("phone").item(0).getTextContent();
                String email = el.getElementsByTagName("email").item(0).getTextContent();
                String area = el.getElementsByTagName("area").item(0).getTextContent();
                String city = el.getElementsByTagName("city").item(0).getTextContent();
            }
        }
    }

Iterate over all children and nl.item(i).getNodeType() == Node.ELEMENT_NODE is used to filter text nodes out. If there is nothing else in XML what remains are staff nodes.

For each node under stuff (name, phone, email, area, city)

 el.getElementsByTagName("name").item(0).getTextContent(); 

el.getElementsByTagName("name") will extract the "name" nodes under stuff, .item(0) will get you the first node and .getTextContent() will get the text content inside.

Edit: Since we have jackson I would do this in a different way. Define a pojo for the object:

public class Staff {
    private String name;
    private String phone;
    private String email;
    private String area;
    private String city;
...getters setters
}

Then using jackson:

    JsonNode root = new XmlMapper().readTree(xml.getBytes());
    ObjectMapper mapper = new ObjectMapper();
    root.forEach(node -> consume(node, mapper));



private void consume(JsonNode node, ObjectMapper mapper) {
    try {
        Staff staff = mapper.treeToValue(node, Staff.class);
        //TODO your job with staff
    } catch (JsonProcessingException e) {
        e.printStackTrace();
    }
}