KickJava   Java API By Example, From Geeks To Geeks.

Java > Open Source Codes > freemarker > template > GeneralPurposeNothing


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.
28  *
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
34  * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
35  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
36  * DISCLAIMED. IN NO EVENT SHALL THE VISIGOTH SOFTWARE SOCIETY OR
37  * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
38  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
39  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
40  * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
41  * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
42  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
43  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
44  * SUCH DAMAGE.
45  * ====================================================================
46  *
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.template;
54
55 import java.util.List JavaDoc;
56 import java.util.ArrayList JavaDoc;
57
58 /**
59  * Singleton object representing nothing, used by ?if_exists built-in.
60  * It is meant to be interpreted in the most sensible way possible in various contexts.
61  * This can be returned to avoid exceptions.
62  *
63  * @author <a HREF="mailto:jon@revusky.com">Jonathan Revusky</a>
64  */

65
66 final class GeneralPurposeNothing
67 implements TemplateBooleanModel, TemplateScalarModel, TemplateSequenceModel, TemplateHashModelEx, TemplateMethodModelEx {
68
69     private static final TemplateModel instance = new GeneralPurposeNothing();
70       
71     private static final TemplateCollectionModel EMPTY_COLLECTION = new SimpleCollection(new ArrayList JavaDoc(0));
72
73     private GeneralPurposeNothing() {
74     }
75
76     static TemplateModel getInstance() {
77         return instance;
78     }
79
80     public String JavaDoc getAsString() {
81         return "";
82     }
83
84     public boolean getAsBoolean() {
85         return false;
86     }
87
88     public boolean isEmpty() {
89         return true;
90     }
91
92     public int size() {
93         return 0;
94     }
95
96     public TemplateModel get(int i) throws TemplateModelException {
97         throw new TemplateModelException("Empty list");
98     }
99
100     public TemplateModel get(String JavaDoc key) {
101         return null;
102     }
103
104     public Object JavaDoc exec(List JavaDoc args) {
105         return null;
106     }
107     
108     public TemplateCollectionModel keys() {
109         return EMPTY_COLLECTION;
110     }
111
112     public TemplateCollectionModel values() {
113         return EMPTY_COLLECTION;
114     }
115 }
116
Popular Tags