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Java > Open Source Codes > com > caucho > amber > expr > ExistsExpr


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 Software Foundation, Inc.
23  * 59 Temple Place, Suite 330
24  * Boston, MA 02111-1307 USA
25  *
26  * @author Scott Ferguson
27  */
28
29 package com.caucho.amber.expr;
30
31 import com.caucho.amber.query.FromItem;
32 import com.caucho.amber.query.QueryParser;
33 import com.caucho.amber.query.SelectQuery;
34 import com.caucho.util.CharBuffer;
35
36 /**
37  * Represents an exists query expression
38  */
39 public class ExistsExpr extends AbstractAmberExpr {
40   private SelectQuery _query;
41
42   public ExistsExpr(SelectQuery query)
43   {
44     _query = query;
45   }
46
47   /**
48    * Binds the expression as a select item.
49    */
50   public AmberExpr bindSelect(QueryParser parser)
51   {
52     return this;
53   }
54
55   /**
56    * Returns true for a boolean expression.
57    */
58   public boolean isBoolean()
59   {
60     return true;
61   }
62
63   /**
64    * Returns true if the expression uses the from item.
65    */
66   public boolean usesFrom(FromItem from, int type, boolean isNot)
67   {
68     return _query.usesFrom(from, type);
69   }
70
71   /**
72    * Generates the where expression.
73    */
74   public void generateWhere(CharBuffer cb)
75   {
76     cb.append("EXISTS(");
77     cb.append(_query.generateLoadSQL(false));
78     cb.append(')');
79   }
80
81   /**
82    * Generates the (update) where expression.
83    */
84   public void generateUpdateWhere(CharBuffer cb)
85   {
86     generateWhere(cb);
87   }
88
89   /**
90    * Generates the having expression.
91    */
92   public void generateHaving(CharBuffer cb)
93   {
94     generateWhere(cb);
95   }
96 }
97
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