KickJava   Java API By Example, From Geeks To Geeks.

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


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 NullExpr extends Expr {
38   private static final Logger JavaDoc log = Log.open(NullExpr.class);
39
40   NullExpr()
41   {
42   }
43
44   /**
45    * Returns true because the literal is null.
46    */
47   public boolean isNull(QueryContext context)
48     throws SQLException JavaDoc
49   {
50     return true;
51   }
52
53   /**
54    * Returns the type of the expression.
55    */
56   public Class JavaDoc getType()
57   {
58     return String JavaDoc.class;
59   }
60
61   /**
62    * Returns the cost based on the given FromList.
63    */
64   public long subCost(ArrayList JavaDoc<FromItem> fromList)
65   {
66     return 0;
67   }
68
69   /**
70    * Evaluates the literal as a string.
71    */
72   public String JavaDoc evalString(QueryContext context)
73     throws SQLException JavaDoc
74   {
75     return null;
76   }
77
78   public String JavaDoc toString()
79   {
80     return "null";
81   }
82 }
83
Popular Tags