Access inner XML data with Java and Xerces

Question

I am trying to parse a XML document using Xerces, but I cant seem to access the data within the elements, below is a sample XML document;

<sample>
<block>
    <name>tom</name>
    <age>44</age>
    <car>BMW</car>
</block>
<block>
    <name>Jenny</name>
    <age>23</age>
    <car>Ford</car>
</block>
</sample>

SO far the only output I can produce is;

Sample
    block
      name
        age
          car
    block
      name
        age
          car

Which is just a list of the node names. I have tried node.getValue(), but this just returns null, so im guessing thats wrong!

How can I access the data inside? Here is what is the basics so far;

public static void display(String file) {
    try{
        DOMParser parser = new DOMParser();
        parser.parse(file);
        Document doc = parser.getDocument();
        read(doc);
    }
        catch(Exception e){e.printStackTrace(System.err);}
}


public static void read(Node node) {
    if(node == null) {return;}
        int type = node.getNodeType();
        //System.out.print((node));
        switch (type) {
        case Node.DOCUMENT_NODE: {
            display_all(((Document)node).getDocumentElement());
            break;
        }

         case Node.TEXT_NODE:

          break;
        case Node.ELEMENT_NODE: {

            System.out.println(node.getNodeName());

            NodeList child = node.getChildNodes();
            if(child != null) {
                int length = child.getLength();
                for (int i = 0; i < length ; i++) {
                        display_all(child.item(i));
                }
        }

        break;


        }
        }
}

getTextContent()? (mis-typed) But why are you skipping text nodes? — Dave Newton
– Dave Newton, Commented Nov 16, 2011 at 15:20
Gives; Exception in thread "main" java.lang.AbstractMethodError: org.apache.xerces.dom.DeferredTextImpl.getTextContent()Ljava/lang/String; TEXT_NODE is blank because everything i try returns null — Lunar
– Lunar, Commented Nov 16, 2011 at 15:22

Dave Newton · Accepted Answer · 2011-11-16 15:52:07Z

1

getNodeValue() returns the value of a text node, which you currently skip over.

 public static void read(Node node) {
    if (node == null) {
        return;
    }

    int type = node.getNodeType();
    switch (type) {
    case Node.DOCUMENT_NODE: {
        System.out.println("Doc node; name: " + node.getNodeName());
        read(((Document) node).getDocumentElement());
        break;
    }

    case Node.TEXT_NODE:
        System.out.println("Text node; value: " + node.getNodeValue().replaceAll("\\s", ""));
        break;

    case Node.ELEMENT_NODE: {
        System.out.println("Element node; name: " + node.getNodeName());
        NodeList children = node.getChildNodes();
        int length = children.getLength();
        for (int i = 0; i < length; i++) {
            read(children.item(i));
        }
        break;
    }
    }
}

I think where you might be getting confused is how XML is actually structured, and what the children of something like this is:

<element>
  <child_element>foo</child_element>
</element>

The above code snippet may help explain.

It's also why things like dom4j, JAXB, XPath, etc. make things much easier.

answered Nov 16, 2011 at 15:52

Dave Newton

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3 Comments

Lunar Over a year ago

How would i go about missing out the car element and its text value? i think this is where i went wrong!

Dave Newton Over a year ago

@Lunar I'm not sure what you mean; are you trying specifically to get just the car element and its value?

Dave Newton Over a year ago

@Lunar Awesome, glad you worked it out! XML can be a pain; I use XPath-ish stuff almost exclusively now.

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