RdbJoin


1   /**
2    * JORM: an implementation of a generic mapping system for persistent Java
3    *       objects. Two mapping are supported: to RDBMS and to binary files.
4    * Copyright (C) 2001-2003 France Telecom R&D - INRIA
5    *
6    * This library is free software; you can redistribute it and/or
7    * modify it under the terms of the GNU Lesser General Public
8    * License as published by the Free Software Foundation; either
9    * version 2 of the License, or (at your option) any later version.
10   *
11   * This library is distributed in the hope that it will be useful,
12   * but WITHOUT ANY WARRANTY; without even the implied warranty of
13   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
14   * Lesser General Public License for more details.
15   *
16   * You should have received a copy of the GNU Lesser General Public
17   * License along with this library; if not, write to the Free Software
18   * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
19   *
20   * Contact: jorm-team@objectweb.org
21   *
22   */
23  package org.objectweb.jorm.mapper.rdb.metainfo;
24  
25  import org.objectweb.jorm.metainfo.lib.BasicMetaObject;
26  
27  import java.util.ArrayList  ;
28  import java.util.List  ;
29  
30  /**
31   * Implementation of the RdbJoin interface. It represents the structure of a join
32   * between an external table and its corresponding main table.
33   * The join relationship requires two columns represented by
34   * primaryTableColumnName and externalTableColumnName.
35   * As a meta-object the parent is the external table. The main table is retrieved
36   * through the external table.
37   * @see     RdbClassMultiMapping
38   */
39  public class RdbJoin extends BasicMetaObject implements Comparable   {
40      /**
41       * Column names of the primary table involved in the join.
42       */
43      private ArrayList   ptJoinColumnNames;
44  
45      /**
46       * Column names of the external table involved in the join.
47       */
48      private ArrayList   etJoinColumnNames;
49  
50      private String   name;
51      /**
52       * Builds a new BasicRdbJoin object between an external table and its
53       * asociated main table. The list of joined columns is given afterwhile by
54       * calling the addJoinColumnNames.
55       *
56       * @param externalTable the external table of the join.
57       * @param name the name given to the join meta-object
58       */
59      public RdbJoin(RdbExternalTable externalTable, String   name) {
60          super(externalTable);
61          this.name = name;
62          this.ptJoinColumnNames = new ArrayList  ();
63          this.etJoinColumnNames = new ArrayList  ();
64      }
65  
66      /**
67       * Returns the external table involved in the join.
68       * @return the external table involved in the join.
69       */
70  
71      public RdbExternalTable getExternalTable() {
72          return (RdbExternalTable) parent;
73      }
74  
75      /**
76       * Returns the main table involved in the join. Retrieved through the external
77       * table.
78       * @return the external table involved in the join.
79       */
80      public RdbTable getMainTable() {
81          return getExternalTable().getMainTable();
82      }
83      /**
84       * Compares the join to another join. Join meta-object are equal if their names
85       * are equal.
86       * @param o the join meta-object to which comparing this join meta-object
87       * @return true is join mata-objects have the same names
88       */
89      public int compareTo(Object   o) {
90          return name.compareTo(((RdbJoin) o).getName());
91      }
92  
93      /**
94       * Returns the list of the column names of the primary (main) table
95       * involved in the join. If main T1 and ext T2 joined through
96       * T1.c11 == T2.c21 ... T1.c1n == T2.c2n,
97       * then this method returns (c11, ..., c1n)
98       * @return the list of the column names of the primary (main) table
99       * involved in the join.
100      */
101     public List   getPTJoinColumnNames() {
102         return ptJoinColumnNames;
103     }
104 
105     /**
106      * Returns the list of the column names of the primary (main) table
107      * involved in the join. If main T1 and ext T2 joined through
108      * T1.c11 == T2.c21 ... T1.c1n == T2.c2n,
109      * then this method returns (c21, ..., c2n)
110      * @return the list of the column names of the primary (main) table
111      * involved in the join.
112      */
113     public List   getETJoinColumnNames() {
114         return etJoinColumnNames;
115     }
116 
117     /**
118      * Adds two join column names 
119      */
120     public void addJoinColumnNames(String   ptJoinColumnName,
121                                    String   etJoinColumnName) {
122         if (! ptJoinColumnNames.contains( ptJoinColumnName)) {
123             if (! etJoinColumnNames.contains( etJoinColumnName)) {
124                 ptJoinColumnNames.add(ptJoinColumnName);
125                 etJoinColumnNames.add(etJoinColumnName);
126             }
127         }
128     }
129 
130     public String   getName() {
131         return name;
132     }
133 
134     public void setName(String   name) {
135         this.name = name;
136     }
137 }
138
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