Java parse XML parent and child elements with the same name

Question

I'm trying to parse some server settings.

  <server>
    <name>HTTP server</name>
    <ssl>
      <name>HTTPS server</name>
      <listen-port>8051</listen-port>
    </ssl>
    <listen-port>8050</listen-port>
  </server>

I'm trying to parse both listen ports to variables in my Java program, but I only seem to get the SSL port when I also want to parse the other port.

            File inputFile = new File(String.valueOf(Paths.get(serverPath, "config", "config.xml")));
            DocumentBuilderFactory dbFactory = DocumentBuilderFactory.newInstance();
            DocumentBuilder dBuilder = dbFactory.newDocumentBuilder();
            Document doc = dBuilder.parse(inputFile);
            doc.getDocumentElement().normalize();

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

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

                if (node.getNodeType() == Node.ELEMENT_NODE) {
                    Element eElement = (Element) node;

                    try {
                        HttpPort = eElement.getElementsByTagName("listen-port").item(0).getTextContent();
                        System.out.println("Http: " + HttpPort);
                        Node sslSettings = eElement.getElementsByTagName("ssl").item(0);

                        if (nList.getLength() == 1) {
                            Element sslElement = (Element) sslSettings;
                            System.out.println(sslElement);
                            HttpsPort = sslElement.getElementsByTagName("listen-port").item(0).getTextContent();
                            System.out.println("Https: " + HttpsPort);
                        }

When I try to display the HTTP port in above example (the second listen-port XML tag, but in the parent), it shows the SSL port. System.out.println("Https: " + HttpsPort); Seems to work as it should.

Anyone an idea?

Answer 1

You should use XPath to extract the right node like so:

import org.w3c.dom.Document;
import org.xml.sax.InputSource;
import org.xml.sax.SAXException;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.xpath.XPath;
import javax.xml.xpath.XPathConstants;
import javax.xml.xpath.XPathExpressionException;
import javax.xml.xpath.XPathFactory;
import java.io.IOException;
import java.io.StringReader;

public class FindViaXpath {

  private static final String XML =
    " <server>\n" +
      "    <name>HTTP server</name>\n" +
      "    <ssl>\n" +
      "      <name>HTTPS server</name>\n" +
      "      <listen-port>8051</listen-port>\n" +
      "    </ssl>\n" +
      "    <listen-port>8050</listen-port>\n" +
      "  </server>";

  public static void main(String[] args) {
    System.out.println(XML);

    DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
    DocumentBuilder builder = null;
    try {
      builder = factory.newDocumentBuilder();
      StringReader reader = new StringReader(XML);
      InputSource source = new InputSource(reader);
      Document document = builder.parse(source);
      XPath xpath = XPathFactory.newInstance().newXPath();
      String port = (String) xpath.evaluate("//server/listen-port", document, XPathConstants.STRING);
      System.out.println(String.format("Port: %s", port));
    } catch (ParserConfigurationException | SAXException | IOException | XPathExpressionException e) {
      e.printStackTrace();
    }
  }
}