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


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.table.LinkColumns;
34
35 /**
36  * Links two tables.
37  */
38 abstract public class JoinExpr extends AbstractAmberExpr {
39   /**
40    * Returns true for a boolean expression.
41    */
42   public boolean isBoolean()
43   {
44     return true;
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    * Binds the expression as a select item.
57    */
58   public boolean bindToFromItem()
59   {
60     return false;
61   }
62
63   /**
64    * Returns the target join clause.
65    */
66   public FromItem getJoinTarget()
67   {
68     return null;
69   }
70
71   /**
72    * Returns the parent join clause.
73    */
74   public FromItem getJoinParent()
75   {
76     return null;
77   }
78
79   /**
80    * Returns true if the given from item is the parent link.
81    */
82   public boolean isDependent(FromItem parent,
83                              LinkColumns link)
84   {
85     return false;
86   }
87
88   /**
89    * Returns the where clause once the parent is removed
90    */
91   public AmberExpr getWhere()
92   {
93     return null;
94   }
95
96   /**
97    * Returns the id expr with the joined expression.
98    */
99   public AmberExpr replace(KeyColumnExpr id)
100   {
101     return id;
102   }
103
104   /**
105    * Returns the id expr with the joined expression.
106    */
107   public AmberExpr replace(IdExpr id)
108   {
109     return id;
110   }
111 }
112
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