/*
* 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 java.util.List;
import org.apache.avalon.framework.component.Component;
import org.apache.avalon.framework.thread.ThreadSafe;
import org.jaxen.NamespaceContext;
import org.jaxen.dom.DOMXPath;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
/**
* This class defines the implementation of the {@link XPathProcessor}
* component.
*
* To configure it, add the following lines in the
* <file>cocoon.xconf</file> file:
*
* <pre>
* <xpath-processor class="org.apache.cocoon.components.xpath.JaxenProcessorImpl">
* </xpath-processor>
* </pre>
*
* @author <a href="mailto:dev@avalon.apache.org">Avalon Development Team</a>
* @version CVS $Revision: 1.4 $ $Date: 2004/02/28 11:47:15 $ $Author: cziegeler $
*/
public final class JaxenProcessorImpl
extends AbstractProcessorImpl
implements XPathProcessor, Component, ThreadSafe
{
/**
* 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
{
final DOMXPath path = new DOMXPath( str );
path.setNamespaceContext( new JaxenResolver(resolver) );
return path.booleanValueOf( contextNode );
}
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
{
final DOMXPath path = new DOMXPath( str );
path.setNamespaceContext( new JaxenResolver(resolver) );
return path.numberValueOf( contextNode );
}
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
{
final DOMXPath path = new DOMXPath( str );
path.setNamespaceContext( new JaxenResolver(resolver) );
return path.stringValueOf( contextNode );
}
catch( final Exception e )
{
if (getLogger().isDebugEnabled()) {
getLogger().debug("Failed to evaluate '" + str + "'", e);
}
// ignore it
return null;
}
}
/**
* Use an XPath string to select a single node.
*
* @param contextNode The node to start searching from.
* @param str A valid XPath string.
* @param resolver a PrefixResolver, used for resolving namespace prefixes
* @return The first node found that matches the XPath, or null.
*/
public Node selectSingleNode(Node contextNode, String str, PrefixResolver resolver)
{
try
{
final DOMXPath path = new DOMXPath( str );
path.setNamespaceContext( new JaxenResolver(resolver) );
return (Node)path.selectSingleNode( contextNode );
}
catch( final Exception e )
{
if (getLogger().isDebugEnabled()) {
getLogger().debug("Failed to evaluate '" + str + "'", e);
}
// ignore it
return null;
}
}
/**
* Use an XPath string to select a nodelist.
*
* @param contextNode The node to start searching from.
* @param str A valid XPath string.
* @param resolver a PrefixResolver, used for resolving namespace prefixes
* @return A List, should never be null.
*/
public NodeList selectNodeList(Node contextNode, String str, PrefixResolver resolver)
{
try
{
final DOMXPath path = new DOMXPath( str );
path.setNamespaceContext( new JaxenResolver(resolver) );
final List list = path.selectNodes( contextNode );
return new SimpleNodeList( list );
}
catch( final Exception e )
{
if (getLogger().isDebugEnabled()) {
getLogger().debug("Failed to evaluate '" + str + "'", e);
}
// ignore it
return new EmptyNodeList();
}
}
/**
* A Jaxen-specific wrapper for the PrefixResolver.
*/
private static class JaxenResolver implements NamespaceContext
{
private final PrefixResolver resolver;
public JaxenResolver(PrefixResolver resolver)
{
this.resolver = resolver;
}
public String translateNamespacePrefixToUri(String prefix)
{
return resolver.prefixToNamespace(prefix);
}
}
}