RowSource


1   /* =============================================================
2    * SmallSQL : a free Java DBMS library for the Java(tm) platform
3    * =============================================================
4    *
5    * (C) Copyright 2004-2006, by Volker Berlin.
6    *
7    * Project Info:  http://www.smallsql.de/
8    *
9    * This library is free software; you can redistribute it and/or modify it 
10   * under the terms of the GNU Lesser General Public License as published by 
11   * the Free Software Foundation; either version 2.1 of the License, or 
12   * (at your option) any later version.
13   *
14   * This library is distributed in the hope that it will be useful, but 
15   * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY 
16   * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public 
17   * License for more details.
18   *
19   * You should have received a copy of the GNU Lesser General Public
20   * License along with this library; if not, write to the Free Software
21   * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, 
22   * USA.  
23   *
24   * [Java is a trademark or registered trademark of Sun Microsystems, Inc. 
25   * in the United States and other countries.]
26   *
27   * ---------------
28   * RowSource.java
29   * ---------------
30   * Author: Volker Berlin
31   * 
32   */
33  package smallsql.database;
34  
35  import java.sql.*;
36  /**
37   * This is the navigation through the rows of any source.
38   * This is an abstract class and not an interface because interfaces are ever public.
39   * All Implementations are used as a Source in the FROM clause.
40   * 
41   * Know Implementations are:
42   * - Join
43   * - TableResult
44   * - ViewResult
45   * - MemoryResult
46   * - GroupResult (extends from MemoryResult)
47   * - SortedResult
48   * - UnionAll
49   * 
50   * Future Implementations are:
51   * - Inner SELECT
52   * - row function
53   */
54  abstract class RowSource {
55      
56      
57      /**
58       * If this RowSource is scrollable. It means it can scroll in all directions.
59       */
60      abstract boolean isScrollable();
61      
62      /**
63       * Equals to ResultSet.beforeFirst()
64       */
65      abstract void beforeFirst() throws Exception  ;
66  
67      
68      
69      /**
70       * Equals to ResultSet.isBeforeFirst().
71       */
72      boolean isBeforeFirst() throws SQLException{
73          throw Utils.createSQLException("ResultSet is forward only.");
74      }
75  
76      /**
77       * Equals to ResultSet.isFirst().
78       */
79      boolean isFirst() throws SQLException{
80          throw Utils.createSQLException("ResultSet is forward only.");
81      }
82      
83  
84      /**
85       * Equals to ResultSet.first()
86       * @return
87       */
88      abstract boolean first() throws Exception  ;
89  
90      boolean previous() throws Exception  {
91          throw Utils.createSQLException("ResultSet is forward only.");
92      }
93      
94      abstract boolean next() throws Exception  ;
95      
96      
97      boolean last() throws Exception  {
98          throw Utils.createSQLException("ResultSet is forward only.");
99      }
100     
101     
102     /**
103      * Equals to ResultSet.isLast().
104      */
105     boolean isLast() throws Exception  {
106         throw Utils.createSQLException("ResultSet is forward only.");
107     }
108 
109     /**
110      * Equals to ResultSet.isAfterLast().
111      */
112     boolean isAfterLast() throws SQLException, Exception  {
113         throw Utils.createSQLException("ResultSet is forward only.");
114     }
115     
116 
117     abstract void afterLast() throws Exception  ;
118     
119     
120     boolean absolute(int row) throws Exception  {
121         throw Utils.createSQLException("ResultSet is forward only.");
122     }
123     
124     
125     boolean relative(int rows) throws Exception  {
126         throw Utils.createSQLException("ResultSet is forward only.");
127     }
128     
129     
130     abstract int getRow() throws Exception  ;
131     
132     
133     
134     /**
135      * Get a marker for the current row. The method setRowPostion must be reconstruct
136      * the current row. The RowPosition can be a file offset for TableResult.
137      * This is using for SortedResult.
138      * @return The value need be >= 0.
139      * It can be a counter for MemoryResult.
140      */
141     abstract long getRowPosition();
142 
143     /**
144      * Restore the row that was marked with the value. This is using for SortedResult.
145      * @param rowPosition Only values that are return from getRowPosition are valid.
146      */
147     abstract void setRowPosition(long rowPosition) throws Exception  ;
148     
149     /**
150      * Is used for OUTER JOIN to set the RowSource to NULL if the row exists
151      * only in the major RowSource (table)
152      */
153     abstract void nullRow();
154     
155     /**
156      * Is used for JOIN to set both site to "No current row". This is needed if
157      * one site has 0 rows that the getXXX() methods throw this exception.
158      */
159     abstract void noRow();
160     
161     
162     /**
163      * If the current row is inserted in this ResultSet.
164      */
165     abstract boolean rowInserted();
166     
167     /**
168      * If the current row is deleted.
169      */
170     abstract boolean rowDeleted();
171     
172     /**
173      * Returns true if a alias was set and no more alias can be set. 
174      * This is used from the SQLParser
175      * @return 
176      */
177     boolean hasAlias(){
178         return true;
179     }
180     
181 
182     void setAlias(String   name) throws SQLException{
183         throw Utils.createSQLException("Alias not supported for this type of row source." );
184     }
185     
186     /**
187      * Perform some operation on some RowSources per ResultSet. For example the grouping
188      * on GroupResult and sorting on SortedResult.
189      */
190     abstract void execute() throws Exception  ;
191     
192 }
A to Z: JavaDoc & Examples Daily Java News & Articles Open Source Projects Open Source Codes Free Computer Books Remove Frame
Popular Tags