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Java > Open Source Codes > org > apache > commons > jxpath > ri > axes > ChildContext


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.axes;
17
18 import org.apache.commons.jxpath.Pointer;
19 import org.apache.commons.jxpath.ri.EvalContext;
20 import org.apache.commons.jxpath.ri.compiler.NodeTest;
21 import org.apache.commons.jxpath.ri.model.NodeIterator;
22 import org.apache.commons.jxpath.ri.model.NodePointer;
23
24 /**
25  * EvalContext that can walk the "child::", "following-sibling::" and
26  * "preceding-sibling::" axes.
27  *
28  * @author Dmitri Plotnikov
29  * @version $Revision: 1.16 $ $Date: 2004/03/25 03:49:50 $
30  */
31 public class ChildContext extends EvalContext {
32     private NodeTest nodeTest;
33     private boolean startFromParentLocation;
34     private boolean reverse;
35     private NodeIterator iterator;
36
37     public ChildContext(
38         EvalContext parentContext,
39         NodeTest nodeTest,
40         boolean startFromParentLocation,
41         boolean reverse)
42     {
43         super(parentContext);
44         this.nodeTest = nodeTest;
45         this.startFromParentLocation = startFromParentLocation;
46         this.reverse = reverse;
47     }
48
49     public NodePointer getCurrentNodePointer() {
50         if (position == 0) {
51             if (!setPosition(1)) {
52                 return null;
53             }
54         }
55         if (iterator != null) {
56             return iterator.getNodePointer();
57         }
58         else {
59             return null;
60         }
61     }
62
63     /**
64      * This method is called on the last context on the path when only
65      * one value is needed. Note that this will return the whole property,
66      * even if it is a collection. It will not extract the first element
67      * of the collection. For example, "books" will return the collection
68      * of books rather than the first book from that collection.
69      */
70     public Pointer getSingleNodePointer() {
71         if (position == 0) {
72             while (nextSet()) {
73                 prepare();
74                 if (iterator == null) {
75                     return null;
76                 }
77                 // See if there is a property there, singular or collection
78 NodePointer pointer = iterator.getNodePointer();
79                 if (pointer != null) {
80                     return pointer;
81                 }
82             }
83             return null;
84         }
85         return getCurrentNodePointer();
86     }
87
88     public boolean nextNode() {
89         return setPosition(getCurrentPosition() + 1);
90     }
91
92     public void reset() {
93         super.reset();
94         iterator = null;
95     }
96
97     public boolean setPosition(int position) {
98         int oldPosition = getCurrentPosition();
99         super.setPosition(position);
100         if (oldPosition == 0) {
101             prepare();
102         }
103         if (iterator == null) {
104             return false;
105         }
106         return iterator.setPosition(position);
107     }
108
109     /**
110      * Allocates a PropertyIterator.
111      */
112     private void prepare() {
113         NodePointer parent = parentContext.getCurrentNodePointer();
114         if (parent == null) {
115             return;
116         }
117         if (startFromParentLocation) {
118             NodePointer pointer = parent.getParent();
119             iterator = pointer.childIterator(nodeTest, reverse, parent);
120         }
121         else {
122             iterator = parent.childIterator(nodeTest, reverse, null);
123         }
124     }
125 }
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