XPathUtil.java

package com.idega.util.xml;

import javax.xml.namespace.NamespaceContext;
import javax.xml.namespace.QName;
import javax.xml.xpath.XPath;
import javax.xml.xpath.XPathConstants;
import javax.xml.xpath.XPathException;
import javax.xml.xpath.XPathExpression;
import javax.xml.xpath.XPathFactory;

import org.w3c.dom.Node;
import org.w3c.dom.NodeList;

/**
 * when using xpath variables, access to XPathUtil instance needs to be synchronized
 *
 * @author <a href="mailto:civilis@idega.com">Vytautas Čivilis</a>
 * @version $Revision: 1.3 $
 *
 * Last modified: $Date: 2008/10/07 13:34:11 $ by $Author: civilis $
 */
public class XPathUtil {

	public static final String	xformsNS = "http://www.w3.org/2002/xforms",
								xhtmlNS = "http://www.w3.org/1999/xhtml",
								IDEGA_XFORM_NS = "http://idega.com/xforms";

	private XPathExpression xpathExpression;
	private XPathVariableResolverImpl variableResolver;

	public XPathUtil(String xpathExpressionStr) {
		NamespaceContextImpl nmspcContext = new NamespaceContextImpl();
		nmspcContext.addPrefix("idega", IDEGA_XFORM_NS);
		nmspcContext.addPrefix("xf", xformsNS);
		nmspcContext.addPrefix("h", xhtmlNS);
		nmspcContext.addPrefix("chiba", "http://chiba.sourceforge.net/xforms");

		compileXPathExpression(xpathExpressionStr, nmspcContext);
	}

	public XPathUtil(String xpathExpressionStr, Prefix... prefixes) {
		NamespaceContextImpl nmspcContext = new NamespaceContextImpl();

		if (prefixes != null) {
			for (Prefix prefix : prefixes) {
				nmspcContext.addPrefix(prefix.getPrefix(), prefix.getNamespace());
			}
		}

		if (nmspcContext.getPrefix(xformsNS) == null)
			nmspcContext.addPrefix("xf", xformsNS);
		if (nmspcContext.getPrefix(xhtmlNS) == null)
			nmspcContext.addPrefix("h", xhtmlNS);
		if (nmspcContext.getPrefix(IDEGA_XFORM_NS) == null)
			nmspcContext.addPrefix("idega", IDEGA_XFORM_NS);

		compileXPathExpression(xpathExpressionStr, nmspcContext);
	}

	public XPathUtil(String xpathExpressionStr, NamespaceContext nmspcContext) {
		compileXPathExpression(xpathExpressionStr, nmspcContext);
	}

	private void compileXPathExpression(String xpathExpressionStr, NamespaceContext nmspcContext) {
		try {
			XPathFactory factory = XPathFactory.newInstance();
			XPath xpath = factory.newXPath();

			variableResolver = new XPathVariableResolverImpl();
			xpath.setXPathVariableResolver(variableResolver);

			if (nmspcContext != null)
				xpath.setNamespaceContext(nmspcContext);

			xpathExpression = xpath.compile(xpathExpressionStr);
		} catch (XPathException e) {
			throw new RuntimeException("Could not compile XPath expression: " + e.getMessage(), e);
		}
	}

	public <T extends Node>T getNode(Node context) {
		try {
			synchronized (xpathExpression) {
				@SuppressWarnings("unchecked")
				T node = (T)xpathExpression.evaluate(context, XPathConstants.NODE);
				return node;
			}

		} catch (XPathException e) {
			throw new RuntimeException("Could not evaluate XPath expression: " + e.getMessage(), e);
		}
	}

	public NodeList getNodeset(Node context) {
		try {
			synchronized (xpathExpression) {
				return (NodeList)xpathExpression.evaluate(context, XPathConstants.NODESET);
			}

		} catch (XPathException e) {
			throw new RuntimeException("Could not evaluate XPath expression: " + e.getMessage(), e);
		}
	}

	public String getString(Node context) {
		try {
			synchronized (xpathExpression) {
				return (String)xpathExpression.evaluate(context, XPathConstants.STRING);
			}

		} catch (XPathException e) {
			throw new RuntimeException("Could not evaluate XPath expression: " + e.getMessage(), e);
		}
	}

	public Object getObject(Node context, QName objType) {
		try {
			synchronized (xpathExpression) {
				return xpathExpression.evaluate(context, objType);
			}

		} catch (XPathException e) {
			throw new RuntimeException("Could not evaluate XPath expression: " + e.getMessage(), e);
		}
	}

	public void setVariable(QName variable, Object value) {
		variableResolver.addVariable(variable, value);
	}

	public void setVariable(String variable, String value) {
		QName qvariable = new QName(variable);
		setVariable(qvariable, value);
	}

	public void clearVariables() {
		variableResolver.clearVariables();
	}
}