package de.intevation.gnv.geobackend.util;

import javax.xml.namespace.NamespaceContext;
import javax.xml.namespace.QName;

import javax.xml.xpath.XPath;
import javax.xml.xpath.XPathExpressionException;
import javax.xml.xpath.XPathFactory;

import org.apache.log4j.Logger;


/**
 * @author <a href="mailto:ingo.weinzierl@intevation.de">Ingo Weinzierl</a>
 */
public final class XMLUtils {

    private static Logger logger = Logger.getLogger(XMLUtils.class);


    private XMLUtils() {
    }


    public static Object xpath(
        Object           root,
        String           query,
        QName            returnType,
        NamespaceContext namespaceContext
    ) {
        if (root == null) {
            return null;
        }

        try {
            XPath xpath = newXPath(namespaceContext);

            if (xpath != null) {
                return xpath.evaluate(query, root, returnType);
            }
        }
        catch (XPathExpressionException xpee) {
            logger.error(xpee.getLocalizedMessage(), xpee);
        }

        return null;
    }


    public static XPath newXPath(NamespaceContext namespaceContext) {
        XPathFactory factory = XPathFactory.newInstance();
        XPath         xpath  = factory.newXPath();

        if (namespaceContext != null) {
            xpath.setNamespaceContext(namespaceContext);
        }

        return xpath;
    }
}
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