Question

So I have an XML file in the format:

<projectlist>
   <project>
      <name>test</name>
      <type>deploy</type>
      <environment>dev</environment>
      <server>test01</server>
      <server>test02</server>
      <server>test03</server>
   </project>
</projectlist>

I’m trying to parse this file and build an object that I can populate a JListBox with the names and a radiobutton group with the different servers, however each project consists of a different amount of servers. How do I iterate the nodes/childnodes to build the object with multiple servers. Here is snippets of the code I’m using borrowed from a website and some from me and I’m not very good at coding yet so bear with me please. When I debug it starts to parse & build the object but once it gets to the server names it prints a null pointer exception so I’m doing something totally wrong.

public class XMLParser {
    public Project currentProject = new Project();

    public void parseXML() throws Exception {

        try {
            File file = new File("c:\\projectlist.xml");
            DocumentBuilderFactory dbFactory = DocumentBuilderFactory.newInstance();
            DocumentBuilder dBuilder = dbFactory.newDocumentBuilder();
            Document doc = dBuilder.parse(file);
            doc.getDocumentElement().normalize();

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

            for (int temp = 0; temp < nList.getLength(); temp++) {

                Node nNode = nList.item(temp);
                if (nNode.getNodeType() == Node.ELEMENT_NODE) {
                    Element eElement = (Element) nNode;

                    currentProject.SetAppName(getTagValue("name", eElement));
                    currentProject.SetType(getTagValue("type", eElement));
                    currentProject.SetEnvironment(getTagValue("environment", eElement));
                    currentProject.SetServerName(getTagValue("server", eElement));



                }
            }




        } catch (Exception e) {
            e.printStackTrace();
        }

    }
     private static String getTagValue(String sTag, Element eElement) {
            NodeList nlList = eElement.getElementsByTagName(sTag).item(0).getChildNodes();

                Node nValue = (Node) nlList.item(0);

            return nValue.getNodeValue();
          }


public final class Project {
    protected String AppName = null;
    protected String Type = null;
    protected List<String> ServerNames = null;
    protected String Environment = null;

    public void SetAppName(String AppName) {
        this.AppName = AppName;
    }

    public void SetType(String DeployType) {
        this.Type = DeployType;
    }

    public void SetServerName(String ServerName) {
        this.ServerNames.add(ServerName);
    }

    public void SetEnvironment(String Environment) {
        this.Environment = Environment;
    }

    public String getAppName() {
        return AppName;
    }

    public String getType() {
        return Type;
    }

    public List<String> getServerName() {
        return ServerNames;
    }

    public String getEnvironment() {
        return Environment;
    }


}

Answer 1

Your exception is being caused because you didn’t initialize ServerNames in your Project class. Try to initialize it as follows and rerun:

final protected List<String> ServerNames = new ArrayList<String>();