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


1 /**
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43
44 package org.exolab.jms.selector;
45
46 import javax.jms.Message JavaDoc;
47
48
49 /**
50  * This class implements a 'between' expression.
51  * This is a boolean expression of the form:
52  * numeric-expr1 between numeric-expr2 and numeric-expr3
53  * This is equivalent to:
54  * numeric-expr1 >= numeric-expr2 and numeric-expr1 <= numeric-expr3
55  *
56  * @version $Revision: 1.1 $ $Date: 2004/11/26 01:50:44 $
57  * @author <a HREF="mailto:tma@netspace.net.au">Tim Anderson</a>
58  * @see Expression
59  * @see SBool
60  */
61 class BetweenExpression implements Expression {
62
63     /**
64      * Corresponds to numeric-expr1
65      */
66     private final Expression _num1;
67
68     /**
69      * Corresponds to numeric-expr2
70      */
71     private final Expression _num2;
72
73     /**
74      * Corresponds to numeric-expr3
75      */
76     private final Expression _num3;
77
78     /**
79      * The expression context, for error reporting purposes
80      */
81     private static final String JavaDoc CONTEXT = "between expression";
82
83
84     /**
85      * Construct an expression that returns num1 >= num2 and num1 <= num3
86      * when evaluated
87      *
88      * @param num1 arithmetic expression
89      * @param num2 arithmetic expression representing the
90      * lower bound
91      * @param num3 arithmetic expression representing the
92      * upper bound
93      */
94     public BetweenExpression(final Expression num1, final Expression num2,
95                              final Expression num3) {
96         _num1 = num1;
97         _num2 = num2;
98         _num3 = num3;
99     }
100
101     /**
102      * Evaluate the 'between' expression
103      *
104      * @param msg the message to evalulate the expression against
105      * @return an SBool instance
106      * @throws TypeMismatchException if any of the expressions are not numeric
107      */
108     public final SObject evaluate(final Message JavaDoc msg)
109         throws TypeMismatchException {
110         SBool result = null;
111         SNumber val1 = TypeCaster.castToNumber(_num1.evaluate(msg), CONTEXT);
112         if (val1 != null) {
113             SNumber val2 = TypeCaster.castToNumber(_num2.evaluate(msg),
114                 CONTEXT);
115             if (val2 != null) {
116                 SNumber val3 = TypeCaster.castToNumber(_num3.evaluate(msg),
117                     CONTEXT);
118                 if (val3 != null) {
119                     if (val1.greaterEqual(val2).value()
120                         && val1.lessEqual(val3).value()) {
121                         result = SBool.TRUE;
122                     } else {
123                         result = SBool.FALSE;
124                     }
125                 }
126             }
127         }
128         return result;
129     }
130
131     /**
132      * Return a string representation of this expression
133      *
134      * @return a string representation of this expression
135      */
136     public final String JavaDoc toString() {
137         StringBuffer JavaDoc result = new StringBuffer JavaDoc();
138         result.append('(');
139         result.append(_num1.toString());
140         result.append(" between ");
141         result.append(_num2.toString());
142         result.append(" and ");
143         result.append(_num3.toString());
144         result.append(')');
145         return result.toString();
146     }
147
148 } //-- BetweenExpression
149
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