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1   /*
2    * Copyright 2001-2004 (C) MetaStuff, Ltd. All Rights Reserved.
3    * 
4    * This software is open source. 
5    * See the bottom of this file for the licence.
6    * 
7    * $Id: PruningElementStack.java,v 1.9 2004/06/25 08:03:37 maartenc Exp $
8    */
9   
10  package org.dom4j.io;
11  
12  import org.dom4j.Element;
13  import org.dom4j.ElementHandler;
14  
15  /*** <p><code>PruningElementStack</code> is a stack of {@link Element} 
16    * instances which will prune the tree when a path expression is reached. 
17    * This is useful for parsing very large documents where children of the
18    * root element can be processed individually rather than keeping them all
19    * in memory at the same time.</p>
20    *
21    * @author <a href="mailto:james.strachan@metastuff.com">James Strachan</a>
22    * @version $Revision: 1.9 $
23    */
24  class PruningElementStack extends ElementStack {
25  
26      /*** ElementHandler to call when pruning occurs */
27      private ElementHandler elementHandler;
28   
29      /*** the element name path which denotes the node to remove from its parent
30        * when it is complete (i.e. when it is popped from the stack).
31        * The first entry in the path will be a child of the root node
32        */
33      private String[] path;
34  
35      /*** The level at which a path match can occur. 
36        * We match when we have popped the selected node so the 
37        * and the lastElementIndex points to its parent so this
38        * value should be path.length - 2
39        */
40      private int matchingElementIndex;
41      
42      
43      
44      public PruningElementStack(String[] path, ElementHandler elementHandler) {
45          this.path = path;
46          this.elementHandler = elementHandler;
47          checkPath();
48      }
49      
50      public PruningElementStack(String[] path, ElementHandler elementHandler, int defaultCapacity) {
51          super(defaultCapacity);
52          this.path = path;
53          this.elementHandler = elementHandler;
54          checkPath();
55      }
56      
57      public Element popElement() {
58          Element answer = super.popElement();
59          
60          if ( lastElementIndex == matchingElementIndex && lastElementIndex >= 0 ) {
61              // we are popping the correct level in the tree
62              // lets check if the path fits
63              //
64              // NOTE: this is an inefficient way of doing it - we could 
65              // maintain a history of which parts matched?
66              if ( validElement( answer, lastElementIndex + 1 ) ) {
67                  Element parent = null;
68                  for ( int i = 0; i <= lastElementIndex; i++ ) {
69                      parent = stack[i];
70                      if ( ! validElement( parent, i ) ) {
71                          parent = null;
72                          break;
73                      }
74                  }
75                  if ( parent != null ) {
76                      pathMatches(parent, answer);
77                  }
78              }
79          }
80          return answer;
81      }
82      
83      protected void pathMatches(Element parent, Element selectedNode) {
84          //System.out.println( "Matched: " + selectedNode + " about to call handler" );
85          
86          //elementHandler.handle( selectedNode );
87          elementHandler.onEnd(this);
88          
89          //System.out.println( "Pruning: removing " + selectedNode + " from parent: " + parent );
90          parent.remove( selectedNode );
91      }
92      
93      protected boolean validElement(Element element, int index) {
94          String requiredName = path[index];
95          String name = element.getName();
96          if (requiredName == name) { 
97              return true;
98          }
99          if (requiredName != null && name != null ) {
100             return requiredName.equals( name );
101         }
102         return false;
103     }
104     
105     
106     private void checkPath() {
107         if ( path.length < 2 ) {
108             throw new RuntimeException( "Invalid path of length: " + path.length + " it must be greater than 2" );
109         }
110         matchingElementIndex = path.length - 2;
111     }
112 }
113 
114 
115 
116 
117 /*
118  * Redistribution and use of this software and associated documentation
119  * ("Software"), with or without modification, are permitted provided
120  * that the following conditions are met:
121  *
122  * 1. Redistributions of source code must retain copyright
123  *    statements and notices.  Redistributions must also contain a
124  *    copy of this document.
125  *
126  * 2. Redistributions in binary form must reproduce the
127  *    above copyright notice, this list of conditions and the
128  *    following disclaimer in the documentation and/or other
129  *    materials provided with the distribution.
130  *
131  * 3. The name "DOM4J" must not be used to endorse or promote
132  *    products derived from this Software without prior written
133  *    permission of MetaStuff, Ltd.  For written permission,
134  *    please contact dom4j-info@metastuff.com.
135  *
136  * 4. Products derived from this Software may not be called "DOM4J"
137  *    nor may "DOM4J" appear in their names without prior written
138  *    permission of MetaStuff, Ltd. DOM4J is a registered
139  *    trademark of MetaStuff, Ltd.
140  *
141  * 5. Due credit should be given to the DOM4J Project - 
142  *    http://www.dom4j.org
143  *
144  * THIS SOFTWARE IS PROVIDED BY METASTUFF, LTD. AND CONTRIBUTORS
145  * ``AS IS'' AND ANY EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT
146  * NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
147  * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL
148  * METASTUFF, LTD. OR ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
149  * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
150  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
151  * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
152  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
153  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
154  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
155  * OF THE POSSIBILITY OF SUCH DAMAGE.
156  *
157  * Copyright 2001-2004 (C) MetaStuff, Ltd. All Rights Reserved.
158  *
159  * $Id: PruningElementStack.java,v 1.9 2004/06/25 08:03:37 maartenc Exp $
160  */