1 /*
2 * Copyright 2001-2005 (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
8 package org.dom4j.io;
9
10 import org.dom4j.Element;
11 import org.dom4j.ElementHandler;
12
13 /**
14 * <p>
15 * <code>PruningElementStack</code> is a stack of {@link Element}instances
16 * which will prune the tree when a path expression is reached. This is useful
17 * for parsing very large documents where children of the root element can be
18 * processed individually rather than keeping them all in memory at the same
19 * time.
20 * </p>
21 *
22 * @author <a href="mailto:james.strachan@metastuff.com">James Strachan </a>
23 * @version $Revision: 1.11 $
24 */
25 class PruningElementStack extends ElementStack {
26 /** ElementHandler to call when pruning occurs */
27 private ElementHandler elementHandler;
28
29 /**
30 * the element name path which denotes the node to remove from its parent
31 * when it is complete (i.e. when it is popped from the stack). The first
32 * entry in the path will be a child of the root node
33 */
34 private String[] path;
35
36 /**
37 * The level at which a path match can occur. We match when we have popped
38 * the selected node so the and the lastElementIndex points to its parent so
39 * this value should be path.length - 2
40 */
41 private int matchingElementIndex;
42
43 public PruningElementStack(String[] path, ElementHandler elementHandler) {
44 this.path = path;
45 this.elementHandler = elementHandler;
46 checkPath();
47 }
48
49 public PruningElementStack(String[] path, ElementHandler elementHandler,
50 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)
61 && (lastElementIndex >= 0)) {
62 // we are popping the correct level in the tree
63 // lets check if the path fits
64 //
65 // NOTE: this is an inefficient way of doing it - we could
66 // maintain a history of which parts matched?
67 if (validElement(answer, lastElementIndex + 1)) {
68 Element parent = null;
69
70 for (int i = 0; i <= lastElementIndex; i++) {
71 parent = stack[i];
72
73 if (!validElement(parent, i)) {
74 parent = null;
75
76 break;
77 }
78 }
79
80 if (parent != null) {
81 pathMatches(parent, answer);
82 }
83 }
84 }
85
86 return answer;
87 }
88
89 protected void pathMatches(Element parent, Element selectedNode) {
90 elementHandler.onEnd(this);
91 parent.remove(selectedNode);
92 }
93
94 protected boolean validElement(Element element, int index) {
95 String requiredName = path[index];
96 String name = element.getName();
97
98 if (requiredName == name) {
99 return true;
100 }
101
102 if ((requiredName != null) && (name != null)) {
103 return requiredName.equals(name);
104 }
105
106 return false;
107 }
108
109 private void checkPath() {
110 if (path.length < 2) {
111 throw new RuntimeException("Invalid path of length: " + path.length
112 + " it must be greater than 2");
113 }
114
115 matchingElementIndex = path.length - 2;
116 }
117 }
118
119 /*
120 * Redistribution and use of this software and associated documentation
121 * ("Software"), with or without modification, are permitted provided that the
122 * following conditions are met:
123 *
124 * 1. Redistributions of source code must retain copyright statements and
125 * notices. Redistributions must also contain a copy of this document.
126 *
127 * 2. Redistributions in binary form must reproduce the above copyright notice,
128 * this list of conditions and the following disclaimer in the documentation
129 * and/or other materials provided with the distribution.
130 *
131 * 3. The name "DOM4J" must not be used to endorse or promote products derived
132 * from this Software without prior written permission of MetaStuff, Ltd. For
133 * written permission, please contact dom4j-info@metastuff.com.
134 *
135 * 4. Products derived from this Software may not be called "DOM4J" nor may
136 * "DOM4J" appear in their names without prior written permission of MetaStuff,
137 * Ltd. DOM4J is a registered trademark of MetaStuff, Ltd.
138 *
139 * 5. Due credit should be given to the DOM4J Project - http://www.dom4j.org
140 *
141 * THIS SOFTWARE IS PROVIDED BY METASTUFF, LTD. AND CONTRIBUTORS ``AS IS'' AND
142 * ANY EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
143 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
144 * ARE DISCLAIMED. IN NO EVENT SHALL METASTUFF, LTD. OR ITS CONTRIBUTORS BE
145 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
146 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
147 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
148 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
149 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
150 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
151 * POSSIBILITY OF SUCH DAMAGE.
152 *
153 * Copyright 2001-2005 (C) MetaStuff, Ltd. All Rights Reserved.
154 */
Save This Page