XPathExpressionImpl


1   /*
2    * Copyright 2002-2004 The Apache Software Foundation.
3    *
4    * Licensed under the Apache License, Version 2.0 (the "License");
5    * you may not use this file except in compliance with the License.
6    * You may obtain a copy of the License at
7    *
8    *     http://www.apache.org/licenses/LICENSE-2.0
9    *
10   * Unless required by applicable law or agreed to in writing, software
11   * distributed under the License is distributed on an "AS IS" BASIS,
12   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13   * See the License for the specific language governing permissions and
14   * limitations under the License.
15   */
16  /*
17   * $Id$
18   */
19  
20  
21  package org.apache.xpath.domapi;
22  
23  import javax.xml.transform.TransformerException  ;
24  
25  import org.apache.xalan.res.XSLMessages;
26  import org.apache.xml.utils.PrefixResolver;
27  import org.apache.xpath.XPath;
28  import org.apache.xpath.XPathContext;
29  import org.apache.xpath.objects.XObject;
30  import org.apache.xpath.res.XPATHErrorResources;
31  
32  import org.w3c.dom.DOMException  ;
33  import org.w3c.dom.Document  ;
34  import org.w3c.dom.Node  ;
35  import org.w3c.dom.xpath.XPathException;
36  import org.w3c.dom.xpath.XPathExpression;
37  import org.w3c.dom.xpath.XPathNamespace;
38  
39  /**
40   * 
41   * The class provides an implementation of XPathExpression according 
42   * to the DOM L3 XPath Specification, Working Draft 28, March 2002.
43   *
44   * <p>See also the <a HREF='http://www.w3.org/TR/2002/WD-DOM-Level-3-XPath-20020328'>Document Object Model (DOM) Level 3 XPath Specification</a>.</p>
45  
46   * <p>The <code>XPathExpression</code> interface represents a parsed and resolved 
47   * XPath expression.</p>
48   * 
49   * @see org.w3c.dom.xpath.XPathExpression
50   */
51  public class XPathExpressionImpl implements XPathExpression {
52  
53    private PrefixResolver m_resolver;      
54    
55    /**
56     * The xpath object that this expression wraps
57     */
58    private XPath m_xpath;
59    
60    /**
61     * The document to be searched to parallel the case where the XPathEvaluator
62     * is obtained by casting a Document.
63     */  
64    private Document   m_doc = null;  
65  
66      /**
67       * Constructor for XPathExpressionImpl.
68       * 
69       * @param xpath The wrapped XPath object.
70       * @param doc The document to be searched, to parallel the case where''
71       *            the XPathEvaluator is obtained by casting the document.
72       */
73      XPathExpressionImpl(XPath xpath, Document   doc) {
74          m_xpath = xpath;
75          m_doc = doc;
76      }
77  
78      /**
79       *
80       * This method provides an implementation XPathResult.evaluate according 
81       * to the DOM L3 XPath Specification, Working Draft 28, March 2002.
82       *
83       * <p>See also the <a HREF='http://www.w3.org/TR/2002/WD-DOM-Level-3-XPath-20020328'>Document Object Model (DOM) Level 3 XPath Specification</a>.</p>
84       * 
85       * <p>Evaluates this XPath expression and returns a result.</p>
86       * @param contextNode The <code>context</code> is context node for the 
87       *   evaluation of this XPath expression.If the XPathEvaluator was 
88       *   obtained by casting the <code>Document</code> then this must be 
89       *   owned by the same document and must be a <code>Document</code>, 
90       *   <code>Element</code>, <code>Attribute</code>, <code>Text</code>, 
91       *   <code>CDATASection</code>, <code>Comment</code>, 
92       *   <code>ProcessingInstruction</code>, or <code>XPathNamespace</code> 
93       *   node.If the context node is a <code>Text</code> or a 
94       *   <code>CDATASection</code>, then the context is interpreted as the 
95       *   whole logical text node as seen by XPath, unless the node is empty 
96       *   in which case it may not serve as the XPath context.
97       * @param type If a specific <code>type</code> is specified, then the 
98       *   result will be coerced to return the specified type relying on 
99       *   XPath conversions and fail if the desired coercion is not possible. 
100      *   This must be one of the type codes of <code>XPathResult</code>.
101     *  @param result The <code>result</code> specifies a specific result 
102      *   object which may be reused and returned by this method. If this is 
103      *   specified as <code>null</code>or the implementation does not reuse 
104      *   the specified result, a new result object will be constructed and 
105      *   returned.For XPath 1.0 results, this object will be of type 
106      *   <code>XPathResult</code>.
107      * @return The result of the evaluation of the XPath expression.For XPath 
108      *   1.0 results, this object will be of type <code>XPathResult</code>.
109      * @exception XPathException
110      *   TYPE_ERR: Raised if the result cannot be converted to return the 
111      *   specified type.
112      * @exception DOMException
113      *   WRONG_DOCUMENT_ERR: The Node is from a document that is not supported 
114      *   by the XPathEvaluator that created this 
115      *   <code>XPathExpression</code>.
116      *   <br>NOT_SUPPORTED_ERR: The Node is not a type permitted as an XPath 
117      *   context node.   
118      * 
119      * @see org.w3c.dom.xpath.XPathExpression#evaluate(Node, short, XPathResult)
120      * @xsl.usage experimental
121      */
122     public Object   evaluate(
123         Node   contextNode,
124         short type,
125         Object   result)
126         throws XPathException, DOMException   {
127             
128         // If the XPathEvaluator was determined by "casting" the document    
129         if (m_doc != null) {
130         
131             // Check that the context node is owned by the same document
132             if ((contextNode != m_doc) && (!contextNode.getOwnerDocument().equals(m_doc))) {
133                 String   fmsg = XSLMessages.createXPATHMessage(XPATHErrorResources.ER_WRONG_DOCUMENT, null);       
134                 throw new DOMException  (DOMException.WRONG_DOCUMENT_ERR, fmsg);
135             }
136             
137             // Check that the context node is an acceptable node type
138             short nodeType = contextNode.getNodeType();
139             if ((nodeType != Document.DOCUMENT_NODE) &&
140                 (nodeType != Document.ELEMENT_NODE) && 
141                 (nodeType != Document.ATTRIBUTE_NODE) &&
142                 (nodeType != Document.TEXT_NODE) &&
143                 (nodeType != Document.CDATA_SECTION_NODE) &&
144                 (nodeType != Document.COMMENT_NODE) &&
145                 (nodeType != Document.PROCESSING_INSTRUCTION_NODE) &&
146                 (nodeType != XPathNamespace.XPATH_NAMESPACE_NODE)) {
147                     String   fmsg = XSLMessages.createXPATHMessage(XPATHErrorResources.ER_WRONG_NODETYPE, null);       
148                     throw new DOMException  (DOMException.NOT_SUPPORTED_ERR, fmsg);
149             }
150         }
151             
152         //     
153         // If the type is not a supported type, throw an exception and be
154         // done with it!
155         if (!XPathResultImpl.isValidType(type)) {
156             String   fmsg = XSLMessages.createXPATHMessage(XPATHErrorResources.ER_INVALID_XPATH_TYPE, new Object  [] {new Integer  (type)});       
157             throw new XPathException(XPathException.TYPE_ERR,fmsg); // Invalid XPath type argument: {0}               
158         }
159         
160         // Cache xpath context?
161         XPathContext xpathSupport = new XPathContext();
162         
163         // if m_document is not null, build the DTM from the document 
164         if (null != m_doc) {
165             xpathSupport.getDTMHandleFromNode(m_doc);
166         }
167 
168         XObject xobj = null;
169         try {
170             xobj = m_xpath.execute(xpathSupport, contextNode, m_resolver );         
171         } catch (TransformerException   te) {
172             // What should we do here?
173             throw new XPathException(XPathException.INVALID_EXPRESSION_ERR,te.getMessageAndLocation()); 
174         }
175 
176         // Create a new XPathResult object
177         // Reuse result object passed in?
178         // The constructor will check the compatibility of type and xobj and
179         // throw an exception if they are not compatible.
180         return new XPathResultImpl(type,xobj,contextNode);
181     }
182 
183 }
184
A to Z: JavaDoc & Examples Daily Java News & Articles Open Source Projects Open Source Codes Free Computer Books Remove Frame
Popular Tags