/*
* Copyright 2002-2004 The Apache Software Foundation
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
* implied.
*
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.excalibur.xml.xpath;
import org.apache.avalon.framework.thread.ThreadSafe;
import org.apache.avalon.framework.component.Component;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import net.sf.saxon.om.NodeInfo;
import net.sf.saxon.om.SequenceIterator;
import net.sf.saxon.om.Item;
import net.sf.saxon.xpath.XPathException;
import net.sf.saxon.xpath.StandaloneContext;
import net.sf.saxon.TransformerFactoryImpl;
import net.sf.saxon.expr.Expression;
import net.sf.saxon.expr.XPathContext;
import net.sf.saxon.expr.ExpressionTool;
import net.sf.saxon.tinytree.TinyBuilder;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.dom.DOMSource;
import java.util.ArrayList;
/**
* This class defines the implementation of the {@link XPathProcessor}
* component. This implementation depends on Saxon 7.X XSLT processor.
* This implementation was tested with Saxon 7.5 release.
*
* To configure it, add the following lines in the
* <file>cocoon.xconf</file> file:
*
* <pre>
* <xslt-processor class="org.apache.cocoon.components.xpath.Saxon7ProcessorImpl">
* </xslt-processor>
* </pre>
*
* @author <a href="mailto:dev@avalon.apache.org">Avalon Development Team</a>
* @version CVS $Id: Saxon7ProcessorImpl.java,v 1.6 2004/04/02 09:02:37 cziegeler Exp $
*/
public class Saxon7ProcessorImpl
extends AbstractProcessorImpl
implements XPathProcessor, Component, ThreadSafe
{
private static final TransformerFactory factory = new TransformerFactoryImpl();
/**
* Evaluate XPath expression within a context.
*
* @param contextNode The context node.
* @param str A valid XPath string.
* @param resolver a PrefixResolver, used for resolving namespace prefixes
* @return expression result as boolean.
*/
public boolean evaluateAsBoolean(Node contextNode, String str, PrefixResolver resolver)
{
try
{
Item item = evaluateSingle(contextNode, str, resolver);
if (item == null)
{
return false;
}
return Boolean.valueOf(item.getStringValue()).booleanValue();
}
catch (final Exception e)
{
if (getLogger().isDebugEnabled()) {
getLogger().debug("Failed to evaluate '" + str + "'", e);
}
// ignore it
return false;
}
}
/**
* Evaluate XPath expression within a context.
*
* @param contextNode The context node.
* @param str A valid XPath string.
* @param resolver a PrefixResolver, used for resolving namespace prefixes
* @return expression result as number.
*/
public Number evaluateAsNumber(Node contextNode, String str, PrefixResolver resolver)
{
try
{
Item item = evaluateSingle(contextNode, str, resolver);
if (item == null)
{
return null;
}
return Double.valueOf(item.getStringValue());
}
catch (final Exception e)
{
if (getLogger().isDebugEnabled()) {
getLogger().debug("Failed to evaluate '" + str + "'", e);
}
// ignore it
return null;
}
}
/**
* Evaluate XPath expression within a context.
*
* @param contextNode The context node.
* @param str A valid XPath string.
* @param resolver a PrefixResolver, used for resolving namespace prefixes
* @return expression result as string.
*/
public String evaluateAsString(Node contextNode, String str, PrefixResolver resolver) {
try
{
Item item = evaluateSingle(contextNode, str, resolver);
if (item == null)
{
return null;
}
return item.getStringValue();
}
catch (final Exception e)
{
if (getLogger().isDebugEnabled()) {
getLogger().debug("Failed to evaluate '" + str + "'", e);
}
// ignore it
return null;
}
}
public Node selectSingleNode(Node contextNode, String str, PrefixResolver resolver)
{
try
{
Item item = evaluateSingle(contextNode, str, resolver);
return (Node)item;
}
catch (final Exception e)
{
if (getLogger().isDebugEnabled()) {
getLogger().debug("Failed to evaluate '" + str + "'", e);
}
// ignore it
return null;
}
}
public NodeList selectNodeList(Node contextNode, String str, PrefixResolver resolver)
{
try
{
SequenceIterator iterator = evaluate(contextNode, str, resolver);
ArrayList nodes = new ArrayList();
for (Node node = (Node)iterator.current(); node != null; node = (Node)iterator.next())
{
nodes.add(node);
}
return new NodeListImpl((Node[])nodes.toArray());
} catch (final Exception e) {
if (getLogger().isDebugEnabled()) {
getLogger().debug("Failed to evaluate '" + str + "'", e);
}
// ignore it
return null;
}
}
private Item evaluateSingle(Node contextNode, String str, PrefixResolver resolver)
{
try
{
SequenceIterator iterator = evaluate(contextNode, str, resolver);
if (iterator == null)
{
return null;
}
return iterator.current();
}
catch (final Exception e)
{
if (getLogger().isDebugEnabled()) {
getLogger().debug("Failed to evaluate '" + str + "'", e);
}
// ignore it
return null;
}
}
private SequenceIterator evaluate(Node contextNode, String str, PrefixResolver resolver)
{
try
{
if (!(contextNode instanceof NodeInfo))
{
getLogger().debug("Input tree is not SAXON TinyTree, converting");
DOMSource source = new DOMSource(contextNode);
TinyBuilder result = new TinyBuilder();
factory.newTransformer().transform(source, result);
contextNode = (Node)result.getCurrentDocument();
}
Expression expression = ExpressionTool.make(
str, new Saxon7Context((NodeInfo)contextNode, resolver), 0, -1);
XPathContext context = new XPathContext((NodeInfo)contextNode);
return expression.iterate(context);
}
catch (final Exception e)
{
if (getLogger().isDebugEnabled()) {
getLogger().debug("Failed to evaluate '" + str + "'", e);
}
// ignore it
return null;
}
}
private class Saxon7Context extends StandaloneContext
{
private final PrefixResolver resolver;
public Saxon7Context(NodeInfo node, PrefixResolver resolver)
{
super(node);
this.resolver = resolver;
}
public String getURIForPrefix(String prefix) throws XPathException
{
return resolver.prefixToNamespace(prefix);
}
}
}