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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.
*/
package org.apache.xml.security.utils;
import java.lang.reflect.Constructor;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import javax.xml.transform.ErrorListener;
import javax.xml.transform.SourceLocator;
import javax.xml.transform.TransformerException;
import org.apache.xml.security.transforms.implementations.FuncHere;
import org.apache.xml.utils.PrefixResolver;
import org.apache.xml.utils.PrefixResolverDefault;
import org.apache.xpath.Expression;
import org.apache.xpath.XPath;
import org.apache.xpath.XPathContext;
import org.apache.xpath.compiler.FunctionTable;
import org.apache.xpath.objects.XObject;
import org.w3c.dom.Document;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
/**
* An implementation of XPathAPI using Xalan. This supports the "here()" function defined in the digital
* signature spec.
*/
public class XalanXPathAPI implements XPathAPI {
private static org.apache.commons.logging.Log log =
org.apache.commons.logging.LogFactory.getLog(XalanXPathAPI.class);
private String xpathStr = null;
private XPath xpath = null;
private static FunctionTable funcTable = null;
private static boolean installed;
private XPathContext context;
static {
fixupFunctionTable();
}
/**
* 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 xpathnode
* @param str
* @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 NodeList selectNodeList(
Node contextNode, Node xpathnode, String str, Node namespaceNode
) throws TransformerException {
// Execute the XPath, and have it return the result
XObject list = eval(contextNode, xpathnode, str, namespaceNode);
// Return a NodeList.
return list.nodelist();
}
/**
* Evaluate an XPath string and return true if the output is to be included or not.
* @param contextNode The node to start searching from.
* @param xpathnode The XPath node
* @param str The XPath expression
* @param namespaceNode The node from which prefixes in the XPath will be resolved to namespaces.
*/
public boolean evaluate(Node contextNode, Node xpathnode, String str, Node namespaceNode)
throws TransformerException {
XObject object = eval(contextNode, xpathnode, str, namespaceNode);
return object.bool();
}
/**
* Clear any context information from this object
*/
public void clear() {
xpathStr = null;
xpath = null;
context = null;
}
public synchronized static boolean isInstalled() {
return installed;
}
private XObject eval(Node contextNode, Node xpathnode, String str, Node namespaceNode)
throws TransformerException {
if (context == null) {
context = new XPathContext(xpathnode);
context.setSecureProcessing(true);
}
// 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).
Node resolverNode =
(namespaceNode.getNodeType() == Node.DOCUMENT_NODE)
? ((Document) namespaceNode).getDocumentElement() : namespaceNode;
PrefixResolverDefault prefixResolver = new PrefixResolverDefault(resolverNode);
if (!str.equals(xpathStr)) {
if (str.indexOf("here()") > 0) {
context.reset();
}
xpath = createXPath(str, prefixResolver);
xpathStr = str;
}
// Execute the XPath, and have it return the result
int ctxtNode = context.getDTMHandleFromNode(contextNode);
return xpath.execute(context, ctxtNode, prefixResolver);
}
private XPath createXPath(String str, PrefixResolver prefixResolver) throws TransformerException {
XPath xpath = null;
Class[] classes = new Class[]{String.class, SourceLocator.class, PrefixResolver.class, int.class,
ErrorListener.class, FunctionTable.class};
Object[] objects =
new Object[]{str, null, prefixResolver, Integer.valueOf(XPath.SELECT), null, funcTable};
try {
Constructor constructor = XPath.class.getConstructor(classes);
xpath = (XPath) constructor.newInstance(objects);
} catch (Exception ex) {
if (log.isDebugEnabled()) {
log.debug(ex);
}
}
if (xpath == null) {
xpath = new XPath(str, null, prefixResolver, XPath.SELECT, null);
}
return xpath;
}
private synchronized static void fixupFunctionTable() {
installed = false;
if (log.isDebugEnabled()) {
log.debug("Registering Here function");
}
/**
* Try to register our here() implementation as internal function.
*/
try {
Class[] args = {String.class, Expression.class};
Method installFunction = FunctionTable.class.getMethod("installFunction", args);
if ((installFunction.getModifiers() & Modifier.STATIC) != 0) {
Object[] params = {"here", new FuncHere()};
installFunction.invoke(null, params);
installed = true;
}
} catch (Exception ex) {
log.debug("Error installing function using the static installFunction method", ex);
}
if (!installed) {
try {
funcTable = new FunctionTable();
Class[] args = {String.class, Class.class};
Method installFunction = FunctionTable.class.getMethod("installFunction", args);
Object[] params = {"here", FuncHere.class};
installFunction.invoke(funcTable, params);
installed = true;
} catch (Exception ex) {
log.debug("Error installing function using the static installFunction method", ex);
}
}
if (log.isDebugEnabled()) {
if (installed) {
log.debug("Registered class " + FuncHere.class.getName()
+ " for XPath function 'here()' function in internal table");
} else {
log.debug("Unable to register class " + FuncHere.class.getName()
+ " for XPath function 'here()' function in internal table");
}
}
}
}