使用XPATH从XML/XHTML中提取数据

import java.io.StringReader;

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

import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import org.xml.sax.InputSource;

public class Evaluation {
    public static String extractString(String xmlStr, String xpath)
            throws XPathExpressionException {
        XPathFactory factory = XPathFactory.newInstance();
        XPath xp = factory.newXPath();
        XPathExpression xpe = xp.compile(xpath);
        InputSource is = new InputSource(new StringReader(xmlStr));
        String result = xpe.evaluate(is);
        return result;
    }

    public static NodeList extractNodeList(String xmlStr, String xpath)
            throws XPathExpressionException {
        XPathFactory factory = XPathFactory.newInstance();
        XPath xp = factory.newXPath();
        XPathExpression xpe = xp.compile(xpath);
        InputSource is = new InputSource(new StringReader(xmlStr));
        NodeList result = (NodeList) xpe.evaluate(is, XPathConstants.NODESET);
        return result;
    }

    public static String extractString(Node node, String xpath)
            throws XPathExpressionException {
        XPathFactory factory = XPathFactory.newInstance();
        XPath xp = factory.newXPath();
        XPathExpression xpe = xp.compile(xpath);
        return xpe.evaluate(node);
    }
}