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 */