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Java > Open Source Codes > org > exolab > jms > selector > Literal


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41  * Copyright 2000-2001,2003 (C) Exoffice Technologies Inc. All Rights Reserved.
42  */
43
44 package org.exolab.jms.selector;
45
46 import javax.jms.Message JavaDoc;
47
48
49 /**
50  * This class implements a literal expression.
51  *
52  * @version $Revision: 1.1 $ $Date: 2004/11/26 01:50:44 $
53  * @author <a HREF="mailto:tma@netspace.net.au">Tim Anderson</a>
54  * @see Expression
55  */
56 class Literal implements Expression {
57
58     /**
59      * The literal value
60      */
61     private SObject _value = null;
62
63     /**
64      * Construct a new <code>Literal</code> expression
65      *
66      * @param value the value of the literal
67      */
68     protected Literal(final SObject value) {
69         _value = value;
70     }
71
72     /**
73      * Construct an approximate numeric literal expression
74      *
75      * @param text the literal text
76      * @return an approximate numeric literal expression
77      * @throws SelectorException if <code>text</code> is not a valid
78      * approximate numeric literal
79      */
80     public static Literal approxNumericLiteral(final String JavaDoc text)
81         throws SelectorException {
82         SDouble value = null;
83         try {
84             value = new SDouble(Double.parseDouble(text));
85         } catch (NumberFormatException JavaDoc exception) {
86             throw new SelectorException("invalid float: " + text);
87         }
88         return new Literal(value);
89     }
90
91     /**
92      * Construct an exact numeric literal expression
93      *
94      * @param text the literal text
95      * @return an exact numeric literal expression
96      * @throws SelectorException if <code>text</code> is not a valid exact
97      * numeric literal
98      */
99     public static Literal exactNumericLiteral(final String JavaDoc text)
100         throws SelectorException {
101         SLong value = null;
102         try {
103             value = new SLong(Long.decode(text).longValue());
104         } catch (NumberFormatException JavaDoc exception) {
105             throw new SelectorException("invalid integer: " + text);
106         }
107         return new Literal(value);
108     }
109
110     /**
111      * Construct a string literal expression
112      *
113      * @param text the literal text
114      * @return a string literal expression
115      */
116     public static Literal stringLiteral(final String JavaDoc text) {
117         return new Literal(new SString(text)) {
118
119             public final String JavaDoc toString() {
120                 return "'" + this.getValue().toString() + "'";
121             }
122         };
123     }
124
125     /**
126      * Construct a boolean literal expression
127      *
128      * @param value the boolean literal value
129      * @return a boolean literal expression
130      */
131     public static Literal booleanLiteral(final boolean value) {
132         SBool bool = SBool.FALSE;
133         if (value) {
134             bool = SBool.TRUE;
135         }
136         return new Literal(bool);
137     }
138
139     /**
140      * Evaluate the expression
141      *
142      * @param msg the message to use to obtain any header identifier and
143      * property values
144      * @return the evaluated result, or <code>null</code> if the value of the
145      * expression is unknown
146      */
147     public final SObject evaluate(final Message JavaDoc msg) {
148         return _value;
149     }
150
151     /**
152      * Return a string representation of the literal
153      *
154      * @return a string representation of the literal
155      */
156     public String JavaDoc toString() {
157         return getValue().toString();
158     }
159
160     /**
161      * Returns the value of the literal
162      *
163      * @return the value of the literal
164      */
165     protected final SObject getValue() {
166         return _value;
167     }
168
169 } //-- Literal
170
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