Java Dom parser reports wrong number of child nodes

Question

I have the following xml file:

<?xml version="1.0" encoding="UTF-8"?>
<users>
<user id="0" firstname="John"/>
</users>

Then I'm trying to parse it with java, but getchildnodes reports wrong number of child nodes.

Java code:

DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
DocumentBuilder builder = factory.newDocumentBuilder();
Document document = builder.parse(this.file);
document.getDocumentElement().normalize();
Element root = document.getDocumentElement();
NodeList nodes = root.getChildNodes();
System.out.println(nodes.getLength());

Result: 3

Also I'm getting NPEs for accessing the nodes attributes, so I'm guessing something's going horribly wrong.

Answer 1

The child nodes consist of elements and text nodes for whitespace. You will want to check the node type before processing the attributes. You may also want to consider using the javax.xml.xpath APIs available in the JDK/JRE starting with Java SE 5.

Example 1

This example demonstrates how to issue an XPath statement against a DOM.

package forum11649396;

import java.io.StringReader;
import javax.xml.parsers.*;
import javax.xml.xpath.*;
import org.w3c.dom.*;
import org.xml.sax.InputSource;

public class Demo {

    public static void main(String[] args) throws Exception {
        String xml = "<?xml version='1.0' encoding='UTF-8'?><users><user id='0' firstname='John'/></users>";

        DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
        DocumentBuilder db = dbf.newDocumentBuilder();
        Document document = db.parse(new InputSource(new StringReader(xml)));

        XPathFactory xpf = XPathFactory.newInstance();
        XPath xpath = xpf.newXPath();
        Element userElement = (Element) xpath.evaluate("/users/user", document, XPathConstants.NODE);
        System.out.println(userElement.getAttribute("id"));
        System.out.println(userElement.getAttribute("firstname"));
    }

}

Example 2

The following example demonstrates how to issue an XPath statement against an InputSource to get a DOM node. This saves you from having to parse the XML into a DOM yourself.

package forum11649396;

import java.io.StringReader;
import javax.xml.xpath.*;
import org.w3c.dom.*;
import org.xml.sax.InputSource;

public class Demo {

    public static void main(String[] args) throws Exception {
        String xml = "<?xml version='1.0' encoding='UTF-8'?><users><user id='0' firstname='John'/></users>";

        XPathFactory xpf = XPathFactory.newInstance();
        XPath xpath = xpf.newXPath();
        InputSource inputSource = new InputSource(new StringReader(xml));
        Element userElement = (Element) xpath.evaluate("/users/user", inputSource, XPathConstants.NODE);
        System.out.println(userElement.getAttribute("id"));
        System.out.println(userElement.getAttribute("firstname"));
    }

}