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Java > Open Source Codes > freemarker > ext > beans > IteratorModel


1 /*
2  * Copyright (c) 2003 The Visigoth Software Society. All rights
3  * reserved.
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5  * Redistribution and use in source and binary forms, with or without
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9  * 1. Redistributions of source code must retain the above copyright
10  * notice, this list of conditions and the following disclaimer.
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12  * 2. Redistributions in binary form must reproduce the above copyright
13  * notice, this list of conditions and the following disclaimer in
14  * the documentation and/or other materials provided with the
15  * distribution.
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17  * 3. The end-user documentation included with the redistribution, if
18  * any, must include the following acknowledgement:
19  * "This product includes software developed by the
20  * Visigoth Software Society (http://www.visigoths.org/)."
21  * Alternately, this acknowledgement may appear in the software itself,
22  * if and wherever such third-party acknowledgements normally appear.
23  *
24  * 4. Neither the name "FreeMarker", "Visigoth", nor any of the names of the
25  * project contributors may be used to endorse or promote products derived
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29  * 5. Products derived from this software may not be called "FreeMarker" or "Visigoth"
30  * nor may "FreeMarker" or "Visigoth" appear in their names
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51  */
52
53 package freemarker.ext.beans;
54
55 import java.util.Iterator JavaDoc;
56 import java.util.NoSuchElementException JavaDoc;
57
58 import freemarker.template.TemplateCollectionModel;
59 import freemarker.template.TemplateModel;
60 import freemarker.template.TemplateModelException;
61 import freemarker.template.TemplateModelIterator;
62
63 /**
64  * <p>A class that adds {@link TemplateModelIterator} functionality to the
65  * {@link Iterator} interface implementers.
66  * </p>
67  * <p>It differs from the {@link freemarker.template.SimpleCollection} in that
68  * it inherits from {@link BeanModel}, and therefore you can call methods on
69  * it directly, even to the effect of calling <tt>iterator.remove()</tt> in
70  * the template.</p> <p>Using the model as a collection model is NOT
71  * thread-safe, as iterators are inherently not thread-safe.
72  * Further, you can iterate over it only once. Attempts to call the
73  * {@link #iterator()} method after it was already driven to the end once will
74  * throw an exception.</p>
75  * @author Attila Szegedi
76  * @version $Id: IteratorModel.java,v 1.26 2003/06/03 13:21:32 szegedia Exp $
77  */
78
79 public class IteratorModel
80 extends
81     BeanModel
82 implements
83     TemplateModelIterator,
84     TemplateCollectionModel
85 {
86     private boolean accessed = false;
87     
88     /**
89      * Creates a new model that wraps the specified iterator object.
90      * @param iterator the iterator object to wrap into a model.
91      * @param wrapper the {@link BeansWrapper} associated with this model.
92      * Every model has to have an associated {@link BeansWrapper} instance. The
93      * model gains many attributes from its wrapper, including the caching
94      * behavior, method exposure level, method-over-item shadowing policy etc.
95      */
96     public IteratorModel(Iterator JavaDoc iterator, BeansWrapper wrapper)
97     {
98         super(iterator, wrapper);
99     }
100
101     /**
102      * This allows the iterator to be used in a <tt>&lt;foreach></tt> block.
103      * @return "this"
104      */
105     public TemplateModelIterator iterator() throws TemplateModelException
106     {
107         synchronized(this) {
108             if(accessed) {
109                 throw new TemplateModelException(
110                     "This collection is stateful and can not be iterated over the" +
111                     " second time.");
112             }
113             accessed = true;
114         }
115         return this;
116     }
117     
118     /**
119      * Calls underlying {@link Iterator#hasNext()}.
120      */
121     public boolean hasNext() {
122         return ((Iterator JavaDoc)object).hasNext();
123     }
124
125
126     /**
127      * Calls underlying {@link Iterator#next()} and wraps the result.
128      */
129     public TemplateModel next()
130     throws
131         TemplateModelException
132     {
133         try {
134             return wrap(((Iterator JavaDoc)object).next());
135         }
136         catch(NoSuchElementException JavaDoc e) {
137             throw new TemplateModelException(
138                 "No more elements in the iterator.");
139         }
140     }
141
142     /**
143      * Returns {@link Iterator#hasNext()}. Therefore, an
144      * iterator that has no more element evaluates to false, and an
145      * iterator that has further elements evaluates to true.
146      */
147     public boolean getAsBoolean() {
148         return hasNext();
149     }
150 }
151
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