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Java > Open Source Codes > org > mr > api > jms > selector > syntax > LogicalOperator


1 /*
2  * Copyright 2002 by
3  * <a HREF="http://www.coridan.com">Coridan</a>
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6  * The contents of this file are subject to the Mozilla Public License Version
7  * 1.1 (the "License"); you may not use this file except in compliance with the
8  * License. You may obtain a copy of the License at
9  * http://www.mozilla.org/MPL/
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11  * Software distributed under the License is distributed on an "AS IS" basis,
12  * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
13  * for the specific language governing rights and limitations under the
14  * License.
15  *
16  * The Original Code is "MantaRay" (TM).
17  *
18  * The Initial Developer of the Original Code is Coridan.
19  * Portions created by the Initial Developer are Copyright (C) 2006
20  * Coridan Inc. All Rights Reserved.
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23  * code where applicable.
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25  * Alternatively, the contents of this file may be used under the terms of the
26  * LGPL license (the "GNU LESSER GENERAL PUBLIC LICENSE"), in which case the
27  * provisions of LGPL are applicable instead of those above. If you wish to
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32  * If you do not delete the provisions above, a recipient may use your version
33  * of this file under either the MPL or the GNU LESSER GENERAL PUBLIC LICENSE.
34  
35  *
36  * This library is free software; you can redistribute it and/or modify it
37  * under the terms of the MPL as stated above or under the terms of the GNU
38  * Lesser General Public License as published by the Free Software Foundation;
39  * either version 2.1 of the License, or any later version.
40  *
41  * This library is distributed in the hope that it will be useful, but WITHOUT
42  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
43  * FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
44  * License for more details.
45  */
46 package org.mr.api.jms.selector.syntax;
47
48 import javax.jms.Message JavaDoc;
49
50
51 /**
52  * This class is the base class for all expressions that are boolean binary
53  * operators. These return a boolean result when evaluated, or null
54  * if the result is undefined.
55  *
56  */
57 abstract class LogicalOperator extends BinaryOperator {
58
59     /**
60      * Construct a new <code>LogicalOperator</code>
61      *
62      * @param operator the operator
63      * @param leftHand the left hand side of the expression
64      * @param rightHand the right hand side of the expression
65      */
66     protected LogicalOperator(final String JavaDoc operator, final Expression leftHand,final Expression rightHand) {
67         super(operator, leftHand, rightHand);
68     }//LogicalOperator
69
70     
71     /**
72      * Evaluate the expression
73      *
74      * @param msg the message to use to obtain any header identifier and property values
75      * @return the evaluated result, or <code>null</code> if the value of the expression is unknown
76      * @throws TypeMismatchException if the expression tries to evaluate mismatched types.
77      */
78     public MantaObject evaluate(final Message JavaDoc msg) throws TypeMismatchException {
79         
80         MantaBoolean result = null;
81         MantaObject leftHand = left().evaluate(msg);
82
83         if (leftHand != null) {
84             MantaObject rightHand = right().evaluate(msg);
85             if (rightHand!= null) {
86                 checkTypes(leftHand.type(), rightHand.type());
87                 result = evaluate(leftHand, rightHand);
88             }//if
89 }//if
90 return result;
91     }//evaluate
92
93     
94     /**
95      * Perform a logical comparison
96      *
97      * @param leftHand the left hand side of the expression
98      * @param rightHand the right hand side of the expression
99      * @return the evaluated result
100      */
101     protected MantaBoolean evaluate(final MantaObject leftHand, final MantaObject rightHand) {
102         return null;
103     }//evaluate
104
105     
106     /**
107      * Verifies that the types of expression can be verified.
108      *
109      * @param leftHand the left hand side of the expression
110      * @param rightHand the right hand side of the expression
111      * @throws TypeMismatchException if the types cannot be compared
112      */
113     protected void checkTypes(final Type leftHand, final Type rightHand) throws TypeMismatchException {
114
115         if (leftHand!= rightHand) {
116             StringBuffer JavaDoc msg = new StringBuffer JavaDoc();
117             msg.append("expecting a ");
118             msg.append(leftHand);
119             msg.append(" expression for operator ");
120             msg.append(operator());
121             msg.append(", found a ");
122             msg.append(rightHand);
123             
124             throw new TypeMismatchException(msg.toString());
125         }//checkTypes
126 }//checkTypes
127 }//LogicalOperator
128
129
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