/*
* Copyright 1999-2004 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.taglibs.standard.tag.common.xml;
import java.util.Vector;
import javax.servlet.jsp.JspTagException;
import javax.xml.transform.TransformerException;
import org.apache.taglibs.standard.resources.Resources;
import org.apache.xml.utils.PrefixResolver;
import org.apache.xpath.XPath;
import org.apache.xpath.XPathAPI;
import org.apache.xpath.XPathContext;
import org.apache.xpath.objects.XObject;
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 <a href="http://www.w3.org/TR/xpath">XPath Specification</a>
*
*/
public class JSTLXPathAPI extends XPathAPI {
/**
* Use an XPath string to select a single node.
* XPath namespace prefixes are resolved using the prefixResolver.
*
* @param contextNode The node to start searching from.
* @param str A valid XPath string.
* @param prefixResolver The PrefixResolver using which prefixes in the XPath will be resolved to namespaces.
* @return The first node found that matches the XPath, or null.
*
* @throws JspTagException
*/
public static Node selectSingleNode(
Node contextNode, String str, PrefixResolver prefixResolver)
throws JspTagException {
// Have the XObject return its result as a NodeSetDTM.
NodeIterator nl = selectNodeIterator(contextNode, str, prefixResolver);
// Return the first node, or null
return nl.nextNode();
}
/**
* Use an XPath string to select a single node.
* XPath namespace prefixes are resolved using the prefixResolver.
*
* @param contextNode The node to start searching from.
* @param str A valid XPath string.
* @param prefixResolver The PrefixResolver using which prefixes in the XPath will be resolved to namespaces.
* @return The first node found that matches the XPath, or null.
*
* @throws JspTagException
*/
public static Node selectSingleNode(
Node contextNode, String str, PrefixResolver prefixResolver,
XPathContext xpathSupport ) throws JspTagException {
// Have the XObject return its result as a NodeSetDTM.
NodeIterator nl = selectNodeIterator(contextNode, str, prefixResolver, xpathSupport);
// Return the first node, or null
return nl.nextNode();
}
/**
* Use an XPath string to select a nodelist.
* XPath namespace prefixes are resolved using PrefixResolver.
*
* @param contextNode The node to start searching from.
* @param str A valid XPath string.
* @param prefixResolver The PrefixResolver using which prefixes in the XPath will be resolved to namespaces.
* @return A NodeIterator, should never be null.
*
* @throws JspTagException
*/
public static NodeIterator selectNodeIterator(
Node contextNode, String str, PrefixResolver prefixResolver)
throws JspTagException {
// Execute the XPath, and have it return the result
XObject list = eval(contextNode, str, prefixResolver, null);
// Have the XObject return its result as a NodeSetDTM.
return getNodeIterator(list);
}
/**
* Use an XPath string to select a nodelist.
* XPath namespace prefixes are resolved using PrefixResolver.
*
* @param contextNode The node to start searching from.
* @param str A valid XPath string.
* @param prefixResolver The PrefixResolver using which prefixes in the XPath will be resolved to namespaces.
* @return A NodeIterator, should never be null.
*
* @throws JspTagException
*/
public static NodeIterator selectNodeIterator(
Node contextNode, String str, PrefixResolver prefixResolver,
XPathContext xpathSupport ) throws JspTagException {
// Execute the XPath, and have it return the result
XObject list = eval(contextNode, str, prefixResolver, xpathSupport);
// Have the XObject return its result as a NodeSetDTM.
return getNodeIterator(list);
}
/**
* Use an XPath string to select a nodelist.
* XPath namespace prefixes are resolved using the prefixResolver.
*
* @param contextNode The node to start searching from.
* @param str A valid XPath string.
* @param prefixResolver The PrefixResolver using which prefixes in the XPath will be resolved to namespaces.
* @return A NodeIterator, should never be null.
*
* @throws JspTagException
*/
private static NodeList selectNodeList(
Node contextNode, String str, PrefixResolver prefixResolver)
throws JspTagException {
// Execute the XPath, and have it return the result
XObject list = eval(contextNode, str, prefixResolver, null);
// Return a NodeList.
return getNodeList(list);
}
/**
* Use an XPath string to select a nodelist.
* XPath namespace prefixes are resolved using the prefixResolver.
*
* @param contextNode The node to start searching from.
* @param str A valid XPath string.
* @param prefixResolver The PrefixResolver using which prefixes in the XPath will be resolved to namespaces.
* @return A NodeIterator, should never be null.
*
* @throws JspTagException
*/
public static NodeList selectNodeList(
Node contextNode, String str, PrefixResolver prefixResolver,
XPathContext xpathSupport )
throws JspTagException
{
// Execute the XPath, and have it return the result
XObject list = eval(contextNode, str, prefixResolver, xpathSupport);
// Return a NodeList.
return getNodeList(list);
}
/**
* Returns a NodeIterator from an XObject.
* @param list The XObject from which a NodeIterator is returned.
* @return A NodeIterator, should never be null.
* @throws JspTagException
*/
private static NodeIterator getNodeIterator(XObject list)
throws JspTagException {
try {
return list.nodeset();
} catch (TransformerException ex) {
throw new JspTagException(
Resources.getMessage("XPATH_ERROR_XOBJECT", ex.toString()), ex);
}
}
/**
* Returns a NodeList from an XObject.
* @param list The XObject from which a NodeList is returned.
* @return A NodeList, should never be null.
* @throws JspTagException
*/
static NodeList getNodeList(XObject list)
throws JspTagException {
try {
return list.nodelist();
} catch (TransformerException ex) {
throw new JspTagException(
Resources.getMessage("XPATH_ERROR_XOBJECT", ex.toString()), ex);
}
}
/**
* 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.
* @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 JspTagException
*/
public static XObject eval(
Node contextNode, String str, PrefixResolver prefixResolver,
XPathContext xpathSupport) throws JspTagException {
//System.out.println("eval of XPathContext params: contextNode:str(xpath)"+
// ":prefixResolver:xpathSupport => " + contextNode + ":" + str + ":" +
// prefixResolver + ":" + xpathSupport );
try {
if (xpathSupport == null) {
return eval(contextNode, str, prefixResolver);
}
// 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);
// Execute the XPath, and have it return the result
int ctxtNode = xpathSupport.getDTMHandleFromNode(contextNode);
// System.out.println("Context Node id ( after getDTMHandlerFromNode) => " + ctxtNode );
XObject xobj = xpath.execute(xpathSupport, ctxtNode, prefixResolver);
return xobj;
} catch (TransformerException ex) {
throw new JspTagException(
Resources.getMessage("XPATH_ERROR_EVALUATING_EXPR", str, ex.toString()), ex);
} catch (IllegalArgumentException ex) {
throw new JspTagException(
Resources.getMessage("XPATH_ILLEGAL_ARG_EVALUATING_EXPR", str, ex.toString()), ex);
}
}
public static XObject eval(
Node contextNode, String str, PrefixResolver prefixResolver,
XPathContext xpathSupport, Vector varQNames) throws JspTagException {
//p("***************** eval ");
//p( "contextNode => " + contextNode );
//p( "XPath str => " + str );
//p( "PrefixResolver => " + prefixResolver );
//p( "XPath Context => " + xpathSupport );
//p( "Var QNames => " + varQNames );
//p( "Global Var Size => " + varQNames.size() );
try {
XPath xpath = new XPath(str, null, prefixResolver, XPath.SELECT, null);
xpath.fixupVariables( varQNames, varQNames.size());
// Execute the XPath, and have it return the result
int ctxtNode = xpathSupport.getDTMHandleFromNode(contextNode);
// System.out.println("Context Node id ( after getDTMHandlerFromNode) => " + ctxtNode );
return xpath.execute(xpathSupport, ctxtNode, prefixResolver);
} catch (TransformerException ex) {
throw new JspTagException(
Resources.getMessage("XPATH_ERROR_EVALUATING_EXPR", str, ex.toString()), ex);
} catch (IllegalArgumentException ex) {
throw new JspTagException(
Resources.getMessage("XPATH_ILLEGAL_ARG_EVALUATING_EXPR", str, ex.toString()), ex);
}
}
private static void p(String s) {
System.out.println("[JSTLXPathAPI] " + s);
}
}