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/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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.
*/
/*
* $Id: XPathAPI.java 524807 2007-04-02 15:51:43Z zongaro $
*/
package org.apache.xpath;
import javax.xml.transform.TransformerException;
import org.apache.xml.utils.PrefixResolver;
import org.apache.xml.utils.PrefixResolverDefault;
import org.apache.xpath.objects.XObject;
import org.w3c.dom.Document;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import org.w3c.dom.traversal.NodeIterator;
/**
* The methods in this class are convenience methods into the
* low-level XPath API.
* These functions tend to be a little slow, since a number of objects must be
* created for each evaluation. A faster way is to precompile the
* XPaths using the low-level API, and then just use the XPaths
* over and over.
*
* NOTE: In particular, each call to this method will create a new
* XPathContext, a new DTMManager... and thus a new DTM. That's very
* safe, since it guarantees that you're always processing against a
* fully up-to-date view of your document. But it's also portentially
* very expensive, since you're rebuilding the DTM every time. You should
* consider using an instance of CachedXPathAPI rather than these static
* methods.
*
* @see XPath Specification
* */
public class XPathAPI
{
/**
* Use an XPath string to select a single node. XPath namespace
* prefixes are resolved from the context node, which may not
* be what you want (see the next method).
*
* @param contextNode The node to start searching from.
* @param str A valid XPath string.
* @return The first node found that matches the XPath, or null.
*
* @throws TransformerException
*/
public static Node selectSingleNode(Node contextNode, String str)
throws TransformerException
{
return selectSingleNode(contextNode, str, contextNode);
}
/**
* Use an XPath string to select a single node.
* XPath namespace prefixes are resolved from the namespaceNode.
*
* @param contextNode The node to start searching from.
* @param str A valid XPath string.
* @param namespaceNode The node from which prefixes in the XPath will be resolved to namespaces.
* @return The first node found that matches the XPath, or null.
*
* @throws TransformerException
*/
public static Node selectSingleNode(
Node contextNode, String str, Node namespaceNode)
throws TransformerException
{
// Have the XObject return its result as a NodeSetDTM.
NodeIterator nl = selectNodeIterator(contextNode, str, namespaceNode);
// Return the first node, or null
return nl.nextNode();
}
/**
* Use an XPath string to select a nodelist.
* XPath namespace prefixes are resolved from the contextNode.
*
* @param contextNode The node to start searching from.
* @param str A valid XPath string.
* @return A NodeIterator, should never be null.
*
* @throws TransformerException
*/
public static NodeIterator selectNodeIterator(Node contextNode, String str)
throws TransformerException
{
return selectNodeIterator(contextNode, str, contextNode);
}
/**
* Use an XPath string to select a nodelist.
* XPath namespace prefixes are resolved from the namespaceNode.
*
* @param contextNode The node to start searching from.
* @param str A valid XPath string.
* @param namespaceNode The node from which prefixes in the XPath will be resolved to namespaces.
* @return A NodeIterator, should never be null.
*
* @throws TransformerException
*/
public static NodeIterator selectNodeIterator(
Node contextNode, String str, Node namespaceNode)
throws TransformerException
{
// Execute the XPath, and have it return the result
XObject list = eval(contextNode, str, namespaceNode);
// Have the XObject return its result as a NodeSetDTM.
return list.nodeset();
}
/**
* Use an XPath string to select a nodelist.
* XPath namespace prefixes are resolved from the contextNode.
*
* @param contextNode The node to start searching from.
* @param str A valid XPath string.
* @return A NodeIterator, should never be null.
*
* @throws TransformerException
*/
public static NodeList selectNodeList(Node contextNode, String str)
throws TransformerException
{
return selectNodeList(contextNode, str, contextNode);
}
/**
* Use an XPath string to select a nodelist.
* XPath namespace prefixes are resolved from the namespaceNode.
*
* @param contextNode The node to start searching from.
* @param str A valid XPath string.
* @param namespaceNode The node from which prefixes in the XPath will be resolved to namespaces.
* @return A NodeIterator, should never be null.
*
* @throws TransformerException
*/
public static NodeList selectNodeList(
Node contextNode, String str, Node namespaceNode)
throws TransformerException
{
// Execute the XPath, and have it return the result
XObject list = eval(contextNode, str, namespaceNode);
// Return a NodeList.
return list.nodelist();
}
/**
* Evaluate XPath string to an XObject. Using this method,
* XPath namespace prefixes will be resolved from the namespaceNode.
* @param contextNode The node to start searching from.
* @param str A valid XPath string.
* @return An XObject, which can be used to obtain a string, number, nodelist, etc, should never be null.
* @see org.apache.xpath.objects.XObject
* @see org.apache.xpath.objects.XNull
* @see org.apache.xpath.objects.XBoolean
* @see org.apache.xpath.objects.XNumber
* @see org.apache.xpath.objects.XString
* @see org.apache.xpath.objects.XRTreeFrag
*
* @throws TransformerException
*/
public static XObject eval(Node contextNode, String str)
throws TransformerException
{
return eval(contextNode, str, contextNode);
}
/**
* Evaluate XPath string to an XObject.
* XPath namespace prefixes are resolved from the namespaceNode.
* The implementation of this is a little slow, since it creates
* a number of objects each time it is called. This could be optimized
* to keep the same objects around, but then thread-safety issues would arise.
*
* @param contextNode The node to start searching from.
* @param str A valid XPath string.
* @param namespaceNode The node from which prefixes in the XPath will be resolved to namespaces.
* @return An XObject, which can be used to obtain a string, number, nodelist, etc, should never be null.
* @see org.apache.xpath.objects.XObject
* @see org.apache.xpath.objects.XNull
* @see org.apache.xpath.objects.XBoolean
* @see org.apache.xpath.objects.XNumber
* @see org.apache.xpath.objects.XString
* @see org.apache.xpath.objects.XRTreeFrag
*
* @throws TransformerException
*/
public static XObject eval(Node contextNode, String str, Node namespaceNode)
throws TransformerException
{
// Since we don't have a XML Parser involved here, install some default support
// for things like namespaces, etc.
// (Changed from: XPathContext xpathSupport = new XPathContext();
// because XPathContext is weak in a number of areas... perhaps
// XPathContext should be done away with.)
// Create an XPathContext that doesn't support pushing and popping of
// variable resolution scopes. Sufficient for simple XPath 1.0 expressions.
XPathContext xpathSupport = new XPathContext(false);
// Create an object to resolve namespace prefixes.
// XPath namespaces are resolved from the input context node's document element
// if it is a root node, or else the current context node (for lack of a better
// resolution space, given the simplicity of this sample code).
PrefixResolverDefault prefixResolver = new PrefixResolverDefault(
(namespaceNode.getNodeType() == Node.DOCUMENT_NODE)
? ((Document) namespaceNode).getDocumentElement() : namespaceNode);
// Create the XPath object.
XPath xpath = new XPath(str, null, prefixResolver, XPath.SELECT, null);
// Execute the XPath, and have it return the result
// return xpath.execute(xpathSupport, contextNode, prefixResolver);
int ctxtNode = xpathSupport.getDTMHandleFromNode(contextNode);
return xpath.execute(xpathSupport, ctxtNode, prefixResolver);
}
/**
* Evaluate XPath string to an XObject.
* XPath namespace prefixes are resolved from the namespaceNode.
* The implementation of this is a little slow, since it creates
* a number of objects each time it is called. This could be optimized
* to keep the same objects around, but then thread-safety issues would arise.
*
* @param contextNode The node to start searching from.
* @param str A valid XPath string.
* @param prefixResolver Will be called if the parser encounters namespace
* prefixes, to resolve the prefixes to URLs.
* @return An XObject, which can be used to obtain a string, number, nodelist, etc, should never be null.
* @see org.apache.xpath.objects.XObject
* @see org.apache.xpath.objects.XNull
* @see org.apache.xpath.objects.XBoolean
* @see org.apache.xpath.objects.XNumber
* @see org.apache.xpath.objects.XString
* @see org.apache.xpath.objects.XRTreeFrag
*
* @throws TransformerException
*/
public static XObject eval(
Node contextNode, String str, PrefixResolver prefixResolver)
throws TransformerException
{
// Since we don't have a XML Parser involved here, install some default support
// for things like namespaces, etc.
// (Changed from: XPathContext xpathSupport = new XPathContext();
// because XPathContext is weak in a number of areas... perhaps
// XPathContext should be done away with.)
// Create the XPath object.
XPath xpath = new XPath(str, null, prefixResolver, XPath.SELECT, null);
// Create an XPathContext that doesn't support pushing and popping of
// variable resolution scopes. Sufficient for simple XPath 1.0 expressions.
XPathContext xpathSupport = new XPathContext(false);
// Execute the XPath, and have it return the result
int ctxtNode = xpathSupport.getDTMHandleFromNode(contextNode);
return xpath.execute(xpathSupport, ctxtNode, prefixResolver);
}
}
