Java tutorial
/** * 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 org.apache.xml.dtm.DTMManager; import org.apache.xml.security.transforms.implementations.FuncHere; import org.apache.xml.security.transforms.implementations.FuncHereContext; import org.apache.xml.utils.PrefixResolver; import org.apache.xml.utils.PrefixResolverDefault; import org.apache.xpath.CachedXPathAPI; 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.*; import javax.xml.transform.ErrorListener; import javax.xml.transform.SourceLocator; import javax.xml.transform.TransformerException; import java.lang.reflect.Constructor; import java.lang.reflect.Method; import java.lang.reflect.Modifier; /** * * @author $Author: coheigea $ */ public class CachedXPathFuncHereAPI { private static org.apache.commons.logging.Log log = org.apache.commons.logging.LogFactory .getLog(CachedXPathFuncHereAPI.class); /** * XPathContext, and thus DTMManager and DTMs, persists through multiple * calls to this object. */ FuncHereContext funcHereContext = null; /** Field dtmManager */ DTMManager dtmManager = null; XPathContext context = null; String xpathStr = null; XPath xpath = null; static FunctionTable funcTable = null; static { fixupFunctionTable(); } /** * Method getFuncHereContext * @return the context for this object * */ public FuncHereContext getFuncHereContext() { return this.funcHereContext; } /** * Constructor CachedXPathFuncHereAPI * * @param existingXPathContext */ public CachedXPathFuncHereAPI(XPathContext existingXPathContext) { this.dtmManager = existingXPathContext.getDTMManager(); this.context = existingXPathContext; } /** * Constructor CachedXPathFuncHereAPI * * @param previouslyUsed */ public CachedXPathFuncHereAPI(CachedXPathAPI previouslyUsed) { this.dtmManager = previouslyUsed.getXPathContext().getDTMManager(); this.context = previouslyUsed.getXPathContext(); } /** * 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 xpathnode A Node containing a valid XPath string. * @return The first node found that matches the XPath, or null. * * @throws TransformerException */ public Node selectSingleNode(Node contextNode, Node xpathnode) throws TransformerException { return selectSingleNode(contextNode, xpathnode, 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 xpathnode * @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 Node selectSingleNode(Node contextNode, Node xpathnode, Node namespaceNode) throws TransformerException { NodeList nl = selectNodeList(contextNode, xpathnode, getStrFromNode(xpathnode), namespaceNode); // Return the first node, or null if (nl == null) { return null; } return nl.item(0); } /** * 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 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 xpathnode * @param str * @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 XObject eval(Node contextNode, Node xpathnode, String str, Node namespaceNode) throws TransformerException { if (this.funcHereContext == null) { this.funcHereContext = new FuncHereContext(xpathnode, this.dtmManager); } // 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); if (!str.equals(xpathStr)) { if (str.indexOf("here()") > 0) { context.reset(); dtmManager = context.getDTMManager(); } xpath = createXPath(str, prefixResolver); xpathStr = str; } // Execute the XPath, and have it return the result // return xpath.execute(xpathSupport, contextNode, prefixResolver); int ctxtNode = this.funcHereContext.getDTMHandleFromNode(contextNode); return xpath.execute(this.funcHereContext, 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 xpathnode * @param str * @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 XObject eval(Node contextNode, Node xpathnode, String str, PrefixResolver prefixResolver) throws TransformerException { if (!str.equals(xpathStr)) { if (str.indexOf("here()") > 0) { context.reset(); dtmManager = context.getDTMManager(); } try { xpath = createXPath(str, prefixResolver); } catch (TransformerException ex) { //Try to see if it is a problem with the classloader. Throwable th = ex.getCause(); if (th instanceof ClassNotFoundException && th.getMessage().indexOf("FuncHere") > 0) { throw new RuntimeException(I18n.translate("endorsed.jdk1.4.0")/*,*/ + ex); } throw ex; } xpathStr = str; } // Execute the XPath, and have it return the result if (this.funcHereContext == null) { this.funcHereContext = new FuncHereContext(xpathnode, this.dtmManager); } int ctxtNode = this.funcHereContext.getDTMHandleFromNode(contextNode); return xpath.execute(this.funcHereContext, 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 (Throwable t) { if (log.isDebugEnabled()) { log.debug(t); } } if (xpath == null) { xpath = new XPath(str, null, prefixResolver, XPath.SELECT, null); } return xpath; } /** * Method getStrFromNode * * @param xpathnode * @return the string for the node. */ public static String getStrFromNode(Node xpathnode) { if (xpathnode.getNodeType() == Node.TEXT_NODE) { // we iterate over all siblings of the context node because eventually, // the text is "polluted" with pi's or comments StringBuffer sb = new StringBuffer(); for (Node currentSibling = xpathnode.getParentNode() .getFirstChild(); currentSibling != null; currentSibling = currentSibling.getNextSibling()) { if (currentSibling.getNodeType() == Node.TEXT_NODE) { sb.append(((Text) currentSibling).getData()); } } return sb.toString(); } else if (xpathnode.getNodeType() == Node.ATTRIBUTE_NODE) { return ((Attr) xpathnode).getNodeValue(); } else if (xpathnode.getNodeType() == Node.PROCESSING_INSTRUCTION_NODE) { return ((ProcessingInstruction) xpathnode).getNodeValue(); } return null; } private static void fixupFunctionTable() { boolean 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 (Throwable t) { log.debug("Error installing function using the static installFunction method", t); } 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 (Throwable t) { log.debug("Error installing function using the static installFunction method", t); } } 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"); } } } }