Question

I have the following XML:

     <ConfigGroup Name="Replication">
        <ValueInteger Name="ResponseTimeout">10</ValueInteger>
        <ValueInteger Name="PingTimeout">2</ValueInteger>
        <ValueInteger Name="ConnectionTimeout">10</ValueInteger>
        <ConfigGroup Name="Pool">
            <ConfigGroup Name="1">
                <ValueString Encrypted="false" Name="Host">10.20.30.40</ValueString>
                <ValueInteger Name="CacheReplicationPort">8899</ValueInteger>
                <ValueInteger Name="RadiusPort">12050</ValueInteger>
                <ValueInteger Name="OtherPort">4868</ValueInteger>
            </ConfigGroup>
            <ConfigGroup Name="2">
                <ValueString Encrypted="false" Name="Host">10.20.30.50</ValueString>
                <ValueInteger Name="CacheReplicationPort">8899</ValueInteger>
                <ValueInteger Name="RadiusPort">12050</ValueInteger>
                <ValueInteger Name="OtherPort">4868</ValueInteger>
            </ConfigGroup>
        </ConfigGroup>
     </ConfigGroup>

I just wondering what is the simplest way to parse this XML in Java – I want the value from the two host elements (e.g. 10.20.30.40 and 10.20.30.50). Note there may be more than two pool entries (or none at all).

I’m having trouble finding a simple example of how to use the various XML parsers for Java.

Any help is much appreciated.

Thanks!

Answer 1

The simplest way to search for what you are looking for, would be XPath.

try {

    //Load the XML File
    DocumentBuilderFactory domFactory = DocumentBuilderFactory.newInstance();
    domFactory.setNamespaceAware(true);
    DocumentBuilder builder = domFactory.newDocumentBuilder();
    Document configuration = builder.parse("configs.xml");

    //Create an XPath expression
    XPathFactory xpathFactory = XPathFactory.newInstance();
    XPath xpath = xpathFactory.newXPath();
    XPathExpression expr = xpath.compile("//ConfigGroup/ValueString[@Name='Host']/text()");

    //Execute the XPath query
    Object result = expr.evaluate(configuration, XPathConstants.NODESET);
    NodeList nodes = (NodeList) result;

    //Parse the results
    for (int i = 0; i < nodes.getLength(); i++) {
        System.out.println(nodes.item(i).getNodeValue()); 
    }
} catch (ParserConfigurationException e) {
    System.out.println("Bad parser configuration");
    e.printStackTrace();
} catch (SAXException e) {
    System.out.println("SAX error loading the file.");
    e.printStackTrace();
} catch (XPathExpressionException e) {
    System.out.println("Bad XPath Expression");
    e.printStackTrace();
} catch (IOException e) {
    System.out.println("IO Error reading the file.");
    e.printStackTrace();
}

The XPath expression

"//ConfigGroup/ValueString[@Name='Host']/text()"

looks for ConfigGroup elements anywhere in your XML, then finds ValueString elements within the ConfigGroup elements, that have a Name attribute with the value “Host”. @Name=Host is like a filter for elements with the name ValueString. And text() at the end, returns the text node of the selected elements.