1 /*
2 * $Header: /home/cvs/jakarta-commons-sandbox/jelly/src/java/org/apache/commons/jelly/expression/ExpressionSupport.java,v 1.6 2002/07/13 01:03:27 plynch Exp $
3 * $Revision: 1.6 $
4 * $Date: 2002/07/13 01:03:27 $
5 *
6 * ====================================================================
7 *
8 * The Apache Software License, Version 1.1
9 *
10 * Copyright (c) 1999-2002 The Apache Software Foundation. All rights
11 * reserved.
12 *
13 * Redistribution and use in source and binary forms, with or without
14 * modification, are permitted provided that the following conditions
15 * are met:
16 *
17 * 1. Redistributions of source code must retain the above copyright
18 * notice, this list of conditions and the following disclaimer.
19 *
20 * 2. Redistributions in binary form must reproduce the above copyright
21 * notice, this list of conditions and the following disclaimer in
22 * the documentation and/or other materials provided with the
23 * distribution.
24 *
25 * 3. The end-user documentation included with the redistribution, if
26 * any, must include the following acknowlegement:
27 * "This product includes software developed by the
28 * Apache Software Foundation (http://www.apache.org/)."
29 * Alternately, this acknowlegement may appear in the software itself,
30 * if and wherever such third-party acknowlegements normally appear.
31 *
32 * 4. The names "The Jakarta Project", "Commons", and "Apache Software
33 * Foundation" must not be used to endorse or promote products derived
34 * from this software without prior written permission. For written
35 * permission, please contact apache@apache.org.
36 *
37 * 5. Products derived from this software may not be called "Apache"
38 * nor may "Apache" appear in their names without prior written
39 * permission of the Apache Group.
40 *
41 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
42 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
43 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
44 * DISCLAIMED. IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
45 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
46 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
47 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
48 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
49 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
50 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
51 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
52 * SUCH DAMAGE.
53 * ====================================================================
54 *
55 * This software consists of voluntary contributions made by many
56 * individuals on behalf of the Apache Software Foundation. For more
57 * information on the Apache Software Foundation, please see
58 * <http://www.apache.org/>.
59 *
60 * $Id: ExpressionSupport.java,v 1.6 2002/07/13 01:03:27 plynch Exp $
61 */
62 package org.apache.commons.jelly.expression;
63
64 import java.util.Collections;
65 import java.util.Collection;
66 import java.util.Enumeration;
67 import java.util.Iterator;
68 import java.util.List;
69 import java.util.Map;
70
71 import org.apache.commons.collections.ArrayIterator;
72 import org.apache.commons.collections.EnumerationIterator;
73 import org.apache.commons.collections.SingletonIterator;
74
75 import org.apache.commons.jelly.JellyContext;
76
77 /*** <p><code>ExpressionSupport</code>
78 * an abstract base class for Expression implementations
79 * which provides default implementations of some of the
80 * typesafe evaluation methods.</p>
81 *
82 * @author <a href="mailto:jstrachan@apache.org">James Strachan</a>
83 * @version $Revision: 1.6 $
84 */
85 public abstract class ExpressionSupport implements Expression {
86
87 protected static final Iterator EMPTY_ITERATOR = Collections.EMPTY_LIST.iterator();
88
89 // inherit javadoc from interface
90 public String evaluateAsString(JellyContext context) {
91 Object value = evaluate(context);
92 if ( value != null ) {
93 return value.toString();
94 }
95 return null;
96 }
97
98 // inherit javadoc from interface
99 public boolean evaluateAsBoolean(JellyContext context) {
100 Object value = evaluate(context);
101 if ( value instanceof Boolean ) {
102 Boolean b = (Boolean) value;
103 return b.booleanValue();
104 }
105 else if ( value instanceof String ) {
106 // return Boolean.getBoolean( (String) value );
107 String str = (String) value;
108
109 if ( str.equals( "on" )
110 ||
111 str.equals( "yes" )
112 ||
113 str.equals( "1" )
114 ||
115 str.equals( "true" ) )
116 {
117 return true;
118 }
119 else
120 {
121 return false;
122 }
123
124 }
125 return false;
126 }
127
128 // inherit javadoc from interface
129 public Iterator evaluateAsIterator(JellyContext context) {
130 Object value = evaluate(context);
131 if ( value == null ) {
132 return EMPTY_ITERATOR;
133 }
134 else
135 if ( value instanceof Iterator ) {
136 return (Iterator) value;
137 }
138 else if ( value instanceof List ) {
139 List list = (List) value;
140 return list.iterator();
141 }
142 else if ( value instanceof Map ) {
143 Map map = (Map) value;
144 return map.entrySet().iterator();
145 }
146 else if ( value.getClass().isArray() ) {
147 return new ArrayIterator( value );
148 }
149 else if ( value instanceof Enumeration ) {
150 return new EnumerationIterator((Enumeration ) value);
151 }
152 else if ( value instanceof Collection ) {
153 Collection collection = (Collection) value;
154 return collection.iterator();
155 }
156 else {
157 // XXX: should we return single iterator?
158 return new SingletonIterator( value );
159 }
160 }
161 }
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