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Java > Open Source Codes > com > caucho > db > sql > IsNullExpr


1 /*
2  * Copyright (c) 1998-2006 Caucho Technology -- all rights reserved
3  *
4  * This file is part of Resin(R) Open Source
5  *
6  * Each copy or derived work must preserve the copyright notice and this
7  * notice unmodified.
8  *
9  * Resin Open Source is free software; you can redistribute it and/or modify
10  * it under the terms of the GNU General Public License as published by
11  * the Free Software Foundation; either version 2 of the License, or
12  * (at your option) any later version.
13  *
14  * Resin Open Source is distributed in the hope that it will be useful,
15  * but WITHOUT ANY WARRANTY; without even the implied warranty of
16  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE, or any warranty
17  * of NON-INFRINGEMENT. See the GNU General Public License for more
18  * details.
19  *
20  * You should have received a copy of the GNU General Public License
21  * along with Resin Open Source; if not, write to the
22  * Free SoftwareFoundation, Inc.
23  * 59 Temple Place, Suite 330
24  * Boston, MA 02111-1307 USA
25  *
26  * @author Scott Ferguson
27  */
28
29 package com.caucho.db.sql;
30
31 import com.caucho.log.Log;
32
33 import java.sql.SQLException JavaDoc;
34 import java.util.ArrayList JavaDoc;
35 import java.util.logging.Logger JavaDoc;
36
37 class IsNullExpr extends Expr {
38   private static final Logger JavaDoc log = Log.open(IsNullExpr.class);
39
40   private Expr _expr;
41   private boolean _isNot;
42
43   IsNullExpr(Expr expr, boolean isNot)
44   {
45     _expr = expr;
46     _isNot = isNot;
47   }
48
49   /**
50    * Binds the expression to the actual tables.
51    */
52   protected Expr bind(Query query)
53     throws SQLException JavaDoc
54   {
55     _expr = _expr.bind(query);
56
57     return this;
58   }
59
60   /**
61    * Returns the type of the expression.
62    */
63   public Class JavaDoc getType()
64   {
65     return boolean.class;
66   }
67
68   /**
69    * Returns the cost based on the given FromList.
70    */
71   public long subCost(ArrayList JavaDoc<FromItem> fromList)
72   {
73     return _expr.subCost(fromList);
74   }
75
76   /**
77    * Evaluates the expression as a boolean
78    *
79    * @param rows the current tuple being evaluated
80    *
81    * @return the boolean value
82    */
83   public int evalBoolean(QueryContext context)
84     throws SQLException JavaDoc
85   {
86     if (_isNot)
87       return ! _expr.isNull(context) ? TRUE : FALSE;
88     else
89       return _expr.isNull(context) ? TRUE : FALSE;
90   }
91
92   /**
93    * Evaluates the expression as a string.
94    *
95    * @param rows the current tuple being evaluated
96    *
97    * @return the string value
98    */
99   public String JavaDoc evalString(QueryContext context)
100     throws SQLException JavaDoc
101   {
102     return (evalBoolean(context) == TRUE) ? "1" : "0";
103   }
104
105   /**
106    * Evaluates aggregate functions during the group phase.
107    *
108    * @param state the current database tuple
109    */
110   public void evalGroup(QueryContext context)
111     throws SQLException JavaDoc
112   {
113     _expr.evalGroup(context);
114   }
115
116   public String JavaDoc toString()
117   {
118     if (_isNot)
119       return _expr + " IS NOT NULL";
120     else
121       return _expr + " IS NULL";
122   }
123 }
124
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