Jakarta Commons Cookbook

7.7. Configuring Applications with XML

Problem

You need to configure an application with an XML document.

Solution

Use an implementation of XMLConfiguration to load configuration parameters from an XML document. The following XML document contains configuration information that is loaded with a DOMConfiguration object:

<?xml version="1.0" encoding="ISO-8859-1" ?>

<engine-config>
    <start-criteria>
        <criteria type="critical">
            Temperature Above -10 Celsius
        </criteria>
        <criteria>
            Fuel tank is not empty
        </criteria>
    </start-criteria>
    <name>
        <first>Tom</first>
        <last>Payne</last>
    </name>
    <horsepower>42</horsepower>
</engine-config>

A DOMConfiguration object uses the Xerces XML parser to parse an entire XML document into a DOM Document object. Subsequent calls to methods on the Configuration interface cause the DOMConfiguration object to traverse nodes in the Document. The code to read in this XML configuration with DOMConfiguration follows:

import org.apache.commons.configuration.Configuration; import org.apache.commons.configuration.DOMConfiguration; String resource = "com/discursive/jccook/configuration/global.xml"; Configuration config = new DOMConfiguration(resource); // Retrieve a list of all Criteria elements List startCriteria = config.getList("start-criteria.criteria"); // Retrieve the value of the first criteria element String firstCriteria = config.getString("start-criteria.criteria(0)"); // Retrieve the type attribute of the first criteria element String firstCriteriaType = config.getString("start-criteria.criteria(0)[@type]"); ...