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Java > Open Source Codes > com > presumo > jms > selector > JmsEquals


1 /**
2  * This file is part of Presumo.
3  *
4  * Presumo is free software; you can redistribute it and/or modify
5  * it under the terms of the GNU General Public License as published by
6  * the Free Software Foundation; either version 2 of the License, or
7  * (at your option) any later version.
8  *
9  * Presumo is distributed in the hope that it will be useful,
10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12  * GNU General Public License for more details.
13  *
14  * You should have received a copy of the GNU General Public License
15  * along with Presumo; if not, write to the Free Software
16  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
17  *
18  *
19  * Copyright 2001 Dan Greff
20  */
21 package com.presumo.jms.selector;
22
23 import javax.jms.Message JavaDoc;
24
25 /**
26  * Expression node for the SQL equals operation.
27  *
28  * @author Dan Greff
29  */
30 final class JmsEquals extends JmsBinaryOperand
31 {
32   static
33   {
34     STRING_REP = " = "; // Used in unparse
35 }
36
37     /////////////////////////////////////////////////////////////////////////
38 // Static Methods //
39 /////////////////////////////////////////////////////////////////////////
40 static JmsEquals getInstance(JmsOperand lvalue, JmsOperand rvalue)
41   {
42     JmsEquals retval;
43
44     retval = (JmsEquals) getInstanceReflective(JmsOperand.JMS_EQUALS, lvalue, rvalue);
45     if (retval == null)
46       retval = new JmsEquals(lvalue, rvalue);
47
48     return retval;
49   }
50
51     /////////////////////////////////////////////////////////////////////////
52 // Constructor //
53 /////////////////////////////////////////////////////////////////////////
54 protected JmsEquals(JmsOperand lvalue, JmsOperand rvalue)
55   {
56     super(lvalue, rvalue);
57   }
58
59
60     /////////////////////////////////////////////////////////////////////////
61 // Package Methods //
62 /////////////////////////////////////////////////////////////////////////
63
64   JmsOperand evaluate(Message JavaDoc msg) throws SelectorFalseException
65   {
66   
67     try {
68       JmsDataType leftSide = (JmsDataType) lvalue.evaluateOnce(msg);
69       JmsDataType rightSide = (JmsDataType) rvalue.evaluateOnce(msg);
70
71       if (leftSide == null | rightSide == null)
72         return JmsBooleanLiteral.UNKNOWN;
73       else
74         return leftSide.eq(rightSide);
75    
76     } catch (ClassCastException JavaDoc cce) {
77       throw SelectorFalseException.getInstance();
78     }
79
80   }
81
82   short getType() { return JmsOperand.JMS_EQUALS; }
83
84 }
85
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