KickJava   Java API By Example, From Geeks To Geeks.

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


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 java.util.ArrayList JavaDoc;
19 import java.util.List JavaDoc;
20
21 import org.apache.commons.jxpath.JXPathException;
22 import org.apache.commons.jxpath.ri.model.NodeIterator;
23 import org.apache.commons.jxpath.ri.model.NodePointer;
24
25 /**
26  * Combines node iterators of all elements of a collection into one
27  * aggregate node iterator.
28  *
29  * @author Dmitri Plotnikov
30  * @version $Revision: 1.3 $ $Date: 2004/02/29 14:17:41 $
31  */
32 public abstract class CollectionNodeIterator implements NodeIterator {
33     private CollectionPointer pointer;
34     private boolean reverse;
35     private NodePointer startWith;
36     private int position;
37     private List JavaDoc collection;
38
39     protected CollectionNodeIterator(
40         CollectionPointer pointer,
41         boolean reverse,
42         NodePointer startWith)
43     {
44         this.pointer = pointer;
45         this.reverse = reverse;
46         this.startWith = startWith;
47     }
48     
49     /**
50      * Implemened by subclasses to produce child/attribute node iterators.
51      */
52     protected abstract NodeIterator
53             getElementNodeIterator(NodePointer elementPointer);
54
55     public int getPosition() {
56         return position;
57     }
58
59     public boolean setPosition(int position) {
60         if (collection == null) {
61             prepare();
62         }
63         
64         if (position < 1 || position > collection.size()) {
65             return false;
66         }
67         this.position = position;
68         return true;
69     }
70
71     public NodePointer getNodePointer() {
72         if (position == 0) {
73             return null;
74         }
75         return (NodePointer) collection.get(position - 1);
76     }
77     
78     private void prepare() {
79         collection = new ArrayList JavaDoc();
80         NodePointer ptr = (NodePointer) pointer.clone();
81         int length = ptr.getLength();
82         for (int i = 0; i < length; i++) {
83             ptr.setIndex(i);
84             NodePointer elementPointer = ptr.getValuePointer();
85             NodeIterator iter = getElementNodeIterator(elementPointer);
86
87             for (int j = 1; iter.setPosition(j); j++) {
88                 NodePointer childPointer = iter.getNodePointer();
89                 if (reverse) {
90                     collection.add(0, childPointer);
91                 }
92                 else {
93                     collection.add(childPointer);
94                 }
95             }
96         }
97         if (startWith != null) {
98             int index = collection.indexOf(startWith);
99             if (index == -1) {
100                 throw new JXPathException(
101                     "Invalid starting pointer for iterator: " + startWith);
102             }
103             while (collection.size() > index) {
104                 if (!reverse) {
105                     collection.remove(collection.size() - 1);
106                 }
107                 else {
108                     collection.remove(0);
109                 }
110             }
111         }
112     }
113 }
114
Popular Tags