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


1 /**
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16  * products derived from this Software without prior written
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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 java.util.HashSet JavaDoc;
47 import java.util.Iterator JavaDoc;
48 import java.util.TreeSet JavaDoc;
49
50 import javax.jms.Message JavaDoc;
51
52
53 /**
54  * This class implements an 'in' expression.
55  * This is an expression that returns a boolean if a identifier's value is one
56  * a set of supplied values. If the identifier is null (undefined), then the
57  * expression evaluates to null.
58  *
59  * @version $Revision: 1.1 $ $Date: 2004/11/26 01:50:44 $
60  * @author <a HREF="mailto:tma@netspace.net.au">Tim Anderson</a>
61  * @see Expression
62  * @see IdentifierExpression
63  * @see SBool
64  */
65 class InExpression extends IdentifierExpression {
66
67     /**
68      * The set of values to compare against
69      */
70     private final HashSet JavaDoc _values;
71
72
73     /**
74      * Construct a new <code>InExpression</code>
75      *
76      * @param ident the identifier
77      * @param values the values to check against
78      */
79     public InExpression(final Identifier ident, final HashSet JavaDoc values) {
80         super(ident);
81         _values = values;
82     }
83
84     /**
85      * Evaluate the expression
86      *
87      * @param msg the message to use to obtain any header identifier and
88      * property values
89      * @return the evaluated result, or <code>null</code> if the value of the
90      * expression is unknown
91      * @throws TypeMismatchException if the expression tries to evaluate
92      * mismatched types.
93      */
94     public final SObject evaluate(final Message JavaDoc msg)
95         throws TypeMismatchException {
96         SBool result = null;
97
98         SString value = TypeCaster.castToString(identifier().evaluate(msg),
99             "in expression");
100         if (value != null) {
101             if (_values.contains(value.getObject())) {
102                 result = SBool.TRUE;
103             } else {
104                 result = SBool.FALSE;
105             }
106         }
107         return result;
108     }
109
110     /**
111      * Return a string representation of this expression.
112      *
113      * @return a string representation of this expression
114      */
115     public final String JavaDoc toString() {
116         StringBuffer JavaDoc result = new StringBuffer JavaDoc();
117         result.append('(');
118         result.append(identifier().toString());
119         result.append(" in (");
120         int i = 0;
121         TreeSet JavaDoc sorted = new TreeSet JavaDoc(_values);
122         // use a TreeSet to ensure that the result is the same for all
123 // runs/implementations. In general, the HashSet should be faster for
124 // individual lookups.
125 for (Iterator JavaDoc iter = sorted.iterator(); iter.hasNext(); i++) {
126             if (i > 0) {
127                 result.append(", ");
128             }
129             result.append("'");
130             result.append((String JavaDoc) iter.next());
131             result.append("'");
132         }
133         result.append("))");
134         return result.toString();
135     }
136
137 } //-- InExpression
138
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