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Java > Open Source Codes > org > apache > commons > jxpath > ri > model > beans > NullElementPointer


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.beans;
17
18 import org.apache.commons.jxpath.JXPathContext;
19 import org.apache.commons.jxpath.ri.QName;
20 import org.apache.commons.jxpath.ri.model.NodePointer;
21
22 /**
23  * Used when there is a need to construct a Pointer for a collection element
24  * that does not exist. For example, if the path is "foo[3]", but the
25  * collection "foo" only has one element or is empty or is null, the
26  * NullElementPointer can be used to capture this situation without putting a
27  * regular NodePointer into an invalid state. Just create a NullElementPointer
28  * with index 2 (= 3 - 1) and a "foo" pointer as the parent.
29  *
30  * @author Dmitri Plotnikov
31  * @version $Revision: 1.17 $ $Date: 2004/03/25 03:49:50 $
32  */
33 public class NullElementPointer extends CollectionPointer {
34
35     public NullElementPointer(NodePointer parent, int index) {
36         super(parent, (Object JavaDoc) null);
37         this.index = index;
38     }
39
40     public QName getName() {
41         return null;
42     }
43
44     public Object JavaDoc getBaseValue() {
45         return null;
46     }
47
48     public Object JavaDoc getImmediateNode() {
49         return null;
50     }
51     
52     public boolean isLeaf() {
53         return true;
54     }
55     
56     public boolean isCollection() {
57         return false;
58     }
59
60     public PropertyPointer getPropertyPointer() {
61         return new NullPropertyPointer(this);
62     }
63
64     public NodePointer getValuePointer() {
65         return new NullPointer(this, getName());
66     }
67
68     public void setValue(Object JavaDoc value) {
69         throw new UnsupportedOperationException JavaDoc(
70             "Collection element does not exist: " + this);
71     }
72
73     public boolean isActual() {
74         return false;
75     }
76
77     public boolean isContainer() {
78         return true;
79     }
80
81     public NodePointer createPath(JXPathContext context) {
82         return parent.createChild(context, null, index);
83     }
84     
85     public NodePointer createPath(JXPathContext context, Object JavaDoc value) {
86         return parent.createChild(context, null, index, value);
87     }
88
89     public int hashCode() {
90         return getImmediateParentPointer().hashCode() + index;
91     }
92
93     public boolean equals(Object JavaDoc object) {
94         if (object == this) {
95             return true;
96         }
97
98         if (!(object instanceof NullElementPointer)) {
99             return false;
100         }
101
102         NullElementPointer other = (NullElementPointer) object;
103         return getImmediateParentPointer() == other.getImmediateParentPointer()
104             && index == other.index;
105     }
106
107     public int getLength() {
108         return 0;
109     }
110     
111     public String JavaDoc asPath() {
112         StringBuffer JavaDoc buffer = new StringBuffer JavaDoc();
113         NodePointer parent = getImmediateParentPointer();
114         if (parent != null) {
115             buffer.append(parent.asPath());
116         }
117         if (index != WHOLE_COLLECTION) {
118             // Address the list[1][2] case
119 if (parent != null && parent.getIndex() != WHOLE_COLLECTION) {
120                 buffer.append("/.");
121             }
122             else if (parent != null
123                     && parent.getImmediateParentPointer() != null
124                     && parent.getImmediateParentPointer().getIndex() !=
125                             WHOLE_COLLECTION)
126             {
127                 buffer.append("/.");
128             }
129             buffer.append("[").append(index + 1).append(']');
130         }
131
132         return buffer.toString();
133     }
134 }
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