| /* |
| * 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. |
| */ |
| /* |
| * $Id$ |
| */ |
| 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. |
| * |
| * This is an alternative for the old XPathAPI class, which provided |
| * static methods for the purpose but had the drawback of |
| * instantiating a new XPathContext (and thus building a new DTMManager, |
| * and new DTMs) each time it was called. XPathAPIObject instead retains |
| * its context as long as the object persists, reusing the DTMs. This |
| * does have a downside: if you've changed your source document, you should |
| * obtain a new XPathAPIObject to continue searching it, since trying to use |
| * the old DTMs will probably yield bad results or malfunction outright... and |
| * the cached DTMs may consume memory until this object and its context are |
| * returned to the heap. Essentially, it's the caller's responsibility to |
| * decide when to discard the cache. |
| * |
| * @see <a href="http://www.w3.org/TR/xpath">XPath Specification</a> |
| * */ |
| public class CachedXPathAPI |
| { |
| /** XPathContext, and thus the document model system (DTMs), persists through multiple |
| calls to this object. This is set in the constructor. |
| */ |
| protected XPathContext xpathSupport; |
| |
| /** |
| * <p>Default constructor. Establishes its own {@link XPathContext}, and hence |
| * its own {@link org.apache.xml.dtm.DTMManager}. |
| * Good choice for simple uses.</p> |
| * <p>Note that any particular instance of {@link CachedXPathAPI} must not be |
| * operated upon by multiple threads without synchronization; we do |
| * not currently support multithreaded access to a single |
| * {@link org.apache.xml.dtm.DTM}.</p> |
| */ |
| public CachedXPathAPI() |
| { |
| // Create an XPathContext that doesn't support pushing and popping of |
| // variable resolution scopes. Sufficient for simple XPath 1.0 expressions. |
| xpathSupport = new XPathContext(false); |
| } |
| |
| /** |
| * <p>This constructor shares its {@link XPathContext} with a pre-existing |
| * {@link CachedXPathAPI}. That allows sharing document models |
| * ({@link org.apache.xml.dtm.DTM}) and previously established location |
| * state.</p> |
| * <p>Note that the original {@link CachedXPathAPI} and the new one should |
| * not be operated upon concurrently; we do not support multithreaded access |
| * to a single {@link org.apache.xml.dtm.DTM} at this time. Similarly, |
| * any particular instance of {@link CachedXPathAPI} must not be operated |
| * upon by multiple threads without synchronization.</p> |
| * <p>%REVIEW% Should this instead do a clone-and-reset on the XPathSupport object?</p> |
| * |
| */ |
| public CachedXPathAPI(CachedXPathAPI priorXPathAPI) |
| { |
| xpathSupport = priorXPathAPI.xpathSupport; |
| } |
| |
| |
| /** Returns the XPathSupport object used in this CachedXPathAPI |
| * |
| * %REVIEW% I'm somewhat concerned about the loss of encapsulation |
| * this causes, but the xml-security folks say they need it. |
| * */ |
| public XPathContext getXPathContext() |
| { |
| return this.xpathSupport; |
| } |
| |
| |
| /** |
| * 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 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 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 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 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 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 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 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 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 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 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); |
| } |
| } |