View Javadoc

1   /*
2    * Copyright 1999-2004 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  package org.apache.commons.jxpath.ri.model.jdom;
17  
18  import java.util.Collections;
19  import java.util.List;
20  
21  import org.apache.commons.jxpath.ri.compiler.NodeTest;
22  import org.apache.commons.jxpath.ri.model.NodeIterator;
23  import org.apache.commons.jxpath.ri.model.NodePointer;
24  import org.jdom.Document;
25  import org.jdom.Element;
26  
27  /***
28   * An iterator of children of a JDOM Node.
29   *
30   * @author Dmitri Plotnikov
31   * @version $Revision: 1.6 $ $Date: 2004/02/29 14:17:40 $
32   */
33  public class JDOMNodeIterator implements NodeIterator {
34      private NodePointer parent;
35      private NodeTest nodeTest;
36  
37      private boolean reverse;
38      private int position = 0;
39      private int index = 0;
40      private List children;
41      private Object child;
42  
43      public JDOMNodeIterator(
44              NodePointer parent, NodeTest nodeTest,
45              boolean reverse, NodePointer startWith)
46      {
47          this.parent = parent;
48          if (startWith != null) {
49              this.child = startWith.getNode();
50          }
51          // TBD: optimize me for different node tests
52          Object node = parent.getNode();
53          if (node instanceof Document) {
54              this.children = ((Document) node).getContent();
55          }
56          else if (node instanceof Element) {
57              this.children = ((Element) node).getContent();
58          }
59          else {
60              this.children = Collections.EMPTY_LIST;
61          }
62          this.nodeTest = nodeTest;
63          this.reverse = reverse;
64      }
65  
66      public NodePointer getNodePointer() {
67          if (child == null) {
68              if (!setPosition(1)) {
69                  return null;
70              }
71              position = 0;
72          }
73  
74          return new JDOMNodePointer(parent, child);
75      }
76  
77      public int getPosition() {
78          return position;
79      }
80  
81      public boolean setPosition(int position) {
82          while (this.position < position) {
83              if (!next()) {
84                  return false;
85              }
86          }
87          while (this.position > position) {
88              if (!previous()) {
89                  return false;
90              }
91          }
92          return true;
93      }
94  
95      /***
96       * This is actually never invoked during the normal evaluation
97       * of xpaths - an iterator is always going forward, never backwards.
98       * So, this is implemented only for completeness and perhaps for
99       * those who use these iterators outside of XPath evaluation.
100      */
101     private boolean previous() {
102         position--;
103         if (!reverse) {
104             while (--index >= 0) {
105                 child = children.get(index);
106                 if (testChild()) {
107                     return true;
108                 }
109             }
110         }
111         else {
112             for (; index < children.size(); index++) {
113                 child = children.get(index);
114                 if (testChild()) {
115                     return true;
116                 }
117             }
118         }
119         return false;
120     }
121 
122     private boolean next() {
123         position++;
124         if (!reverse) {
125             if (position == 1) {
126                 index = 0;
127                 if (child != null) {
128                     index = children.indexOf(child) + 1;
129                 }
130             }
131             else {
132                 index++;
133             }
134             for (; index < children.size(); index++) {
135                 child = children.get(index);
136                 if (testChild()) {
137                     return true;
138                 }
139             }
140             return false;
141         }
142         else {
143             if (position == 1) {
144                 index = children.size() - 1;
145                 if (child != null) {
146                     index = children.indexOf(child) - 1;
147                 }
148             }
149             else {
150                 index--;
151             }
152             for (; index >= 0; index--) {
153                 child = children.get(index);
154                 if (testChild()) {
155                     return true;
156                 }
157             }
158             return false;
159         }
160     }
161 
162     private boolean testChild() {
163         return JDOMNodePointer.testNode(parent, child, nodeTest);
164     }
165 }