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


1 /*
2  * Copyright (c) 2003 The Visigoth Software Society. All rights
3  * reserved.
4  *
5  * Redistribution and use in source and binary forms, with or without
6  * modification, are permitted provided that the following conditions
7  * are met:
8  *
9  * 1. Redistributions of source code must retain the above copyright
10  * notice, this list of conditions and the following disclaimer.
11  *
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.
16  *
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
26  * from this software without prior written permission. For written
27  * permission, please contact visigoths@visigoths.org.
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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
31  * without prior written permission of the Visigoth Software Society.
32  *
33  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
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35  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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47  * This software consists of voluntary contributions made by many
48  * individuals on behalf of the Visigoth Software Society. For more
49  * information on the Visigoth Software Society, please see
50  * http://www.visigoths.org/
51  */
52
53 package freemarker.ext.beans;
54
55 import java.util.Enumeration 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 Enumeration} interface implementers.
66  * </p> <p>Using the model as a collection model is NOT thread-safe, as
67  * enumerations are inherently not thread-safe.
68  * Further, you can iterate over it only once. Attempts to call the
69  * {@link #iterator()} method after it was already driven to the end once will
70  * throw an exception.</p>
71  * @author Attila Szegedi
72  * @version $Id: EnumerationModel.java,v 1.24 2003/06/03 13:21:32 szegedia Exp $
73  */
74
75 public class EnumerationModel
76 extends
77     BeanModel
78 implements
79     TemplateModelIterator,
80     TemplateCollectionModel
81 {
82     private boolean accessed = false;
83     
84     /**
85      * Creates a new model that wraps the specified enumeration object.
86      * @param enumeration the enumeration object to wrap into a model.
87      * @param wrapper the {@link BeansWrapper} associated with this model.
88      * Every model has to have an associated {@link BeansWrapper} instance. The
89      * model gains many attributes from its wrapper, including the caching
90      * behavior, method exposure level, method-over-item shadowing policy etc.
91      */
92     public EnumerationModel(Enumeration JavaDoc enumeration, BeansWrapper wrapper)
93     {
94         super(enumeration, wrapper);
95     }
96
97     /**
98      * This allows the enumeration to be used in a <tt>&lt;foreach></tt> block.
99      * @return "this"
100      */
101     public TemplateModelIterator iterator() throws TemplateModelException
102     {
103         synchronized(this) {
104             if(accessed) {
105                 throw new TemplateModelException(
106                     "This collection is stateful and can not be iterated over the" +
107                     " second time.");
108             }
109             accessed = true;
110         }
111         return this;
112     }
113     
114     /**
115      * Calls underlying {@link Enumeration#nextElement()}.
116      */
117     public boolean hasNext() {
118         return ((Enumeration JavaDoc)object).hasMoreElements();
119     }
120
121
122     /**
123      * Calls underlying {@link Enumeration#nextElement()} and wraps the result.
124      */
125     public TemplateModel next()
126     throws
127         TemplateModelException
128     {
129         try {
130             return wrap(((Enumeration JavaDoc)object).nextElement());
131         }
132         catch(NoSuchElementException JavaDoc e) {
133             throw new TemplateModelException(
134                 "No more elements in the enumeration.");
135         }
136     }
137
138     /**
139      * Returns {@link Enumeration#hasMoreElements()}. Therefore, an
140      * enumeration that has no more element evaluates to false, and an
141      * enumeration that has further elements evaluates to true.
142      */
143     public boolean getAsBoolean() {
144         return hasNext();
145     }
146 }
147
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