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Java > Open Source Codes > com > caucho > amber > query > JoinExpr


1 /*
2  * Copyright (c) 1998-2004 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.amber.query;
30
31 import com.caucho.amber.table.LinkColumns;
32
33 /**
34  * Links two tables.
35  */
36 abstract public class JoinExpr extends AbstractAmberExpr {
37   /**
38    * Returns true for a boolean expression.
39    */
40   public boolean isBoolean()
41   {
42     return true;
43   }
44
45   /**
46    * Binds the expression as a select item.
47    */
48   public AmberExpr bindSelect(QueryParser parser)
49   {
50     return this;
51   }
52
53   /**
54    * Binds the expression as a select item.
55    */
56   public boolean bindToFromItem()
57   {
58     return false;
59   }
60
61   /**
62    * Returns the target join clause.
63    */
64   FromItem getJoinTarget()
65   {
66     return null;
67   }
68
69   /**
70    * Returns the parent join clause.
71    */
72   FromItem getJoinParent()
73   {
74     return null;
75   }
76
77   /**
78    * Returns true if the given from item is the parent link.
79    */
80   boolean isDependent(FromItem parent, LinkColumns link)
81   {
82     return false;
83   }
84
85   /**
86    * Returns the where clause once the parent is removed
87    */
88   public AmberExpr getWhere()
89   {
90     return null;
91   }
92
93   /**
94    * Returns the id expr with the joined expression.
95    */
96   public AmberExpr replace(KeyColumnExpr id)
97   {
98     return id;
99   }
100
101   /**
102    * Returns the id expr with the joined expression.
103    */
104   public AmberExpr replace(IdExpr id)
105   {
106     return id;
107   }
108 }
109
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