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Java > Open Source Codes > smallsql > database > TableView


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  * TableView.java
29  * ---------------
30  * Author: Volker Berlin
31  *
32  * Created on 05.06.2004
33  */
34 package smallsql.database;
35
36 import java.io.*;
37 import java.sql.*;
38
39
40 /**
41  * @author Volker Berlin
42  */
43 abstract class TableView {
44
45     static final int MAGIC_TABLE = 'S' << 24 | 'Q' << 16 | 'L' << 8 | 'T';
46     static final int MAGIC_VIEW = 'S' << 24 | 'Q' << 16 | 'L' << 8 | 'V';
47     static final int TABLE_VIEW_VERSION = 2;
48     static final int TABLE_VIEW_OLD_VERSION = 1;
49     
50     final String JavaDoc name;
51     final Columns columns;
52
53     /**
54      * Mark the last change on the structur of the Table or View.
55      * If this value change then PreparedStatements need to recompile.
56      */
57     private long timestamp = System.currentTimeMillis();
58     
59     static final int LOCK_NONE = 0; // read on READ_COMMITED and READ_UNCOMMITED
60 static final int LOCK_INSERT = 1; // verhindert nur LOCK_TAB
61 static final int LOCK_READ = 2; // Tritt beim Lesen auf und verhindert ein Schreiben der Daten, es kann mehr als ein LOCK_READ pro page auftreten
62 static final int LOCK_WRITE = 3; // Tritt beim Schreiben auf und verhindert jeden weiteren Zugriff, es ist nur ein LOCK_WRITE pro page möglich
63 static final int LOCK_TAB = 4; // Sperre der gesamten Tabelle
64
65
66     TableView(String JavaDoc name, Columns columns){
67         this.name = name;
68         this.columns = columns;
69     }
70     
71     /**
72      * Load a Table or View object.
73      */
74     static TableView load(SSConnection con, Database database, String JavaDoc name) throws SQLException{
75         RandomAccessFile raFile = null;
76         try{
77             String JavaDoc fileName = Utils.createTableViewFileName( database, name );
78             File file = new File( fileName );
79             if(!file.exists())
80                 throw Utils.createSQLException("Table or View '" + name + "' does not exist");
81             raFile = new RandomAccessFile( file, "rw" );
82             int magic = raFile.readInt();
83             int version = raFile.readInt();
84             switch(magic){
85                 case MAGIC_TABLE:
86                 case MAGIC_VIEW:
87                         break;
88                 default:
89                     throw Utils.createSQLException("File '" + fileName + "' is not a valid Table or View store.");
90             }
91             if(version > TABLE_VIEW_VERSION)
92                 throw Utils.createSQLException("File version (" + version + ") of file '" + fileName + "' is to new for this runtume.");
93             if(version < TABLE_VIEW_OLD_VERSION)
94                 throw Utils.createSQLException("File version (" + version + ") of file '" + fileName + "' is to old for this runtume.");
95             if(magic == MAGIC_TABLE)
96                 return new Table( con, name, raFile, raFile.getFilePointer(), version);
97                 return new View ( con, name, raFile, raFile.getFilePointer());
98         }catch(Throwable JavaDoc e){
99             if(raFile != null)
100                 try{
101                     raFile.close();
102                 }catch(Exception JavaDoc e2){
103                     DriverManager.println(e2.toString());
104                 }
105             throw Utils.createSQLException(e);
106         }
107     }
108     
109     
110     File getFile(Database database, String JavaDoc name) throws Exception JavaDoc{
111         return new File( Utils.createTableViewFileName( database, name ) );
112     }
113     
114
115     RandomAccessFile createFile(Database database) throws Exception JavaDoc{
116         File file = getFile( database, name );
117         boolean ok = file.createNewFile();
118         if(!ok) throw Utils.createSQLException("Table or View '" + name + "' already exists.");
119         RandomAccessFile raFile = new RandomAccessFile( file, "rw" );
120         writeMagic(raFile);
121         return raFile;
122     }
123     
124     abstract void writeMagic(RandomAccessFile raFile) throws Exception JavaDoc;
125
126     
127     String JavaDoc getName(){
128         return name;
129     }
130     
131
132     long getTimestamp(){
133         return timestamp;
134     }
135     
136
137     /**
138      * Returns the index of a column name. The first column has the index 0.
139      */
140     final int findColumnIdx(String JavaDoc name){
141         // FIXME auf tree suche umstellen aus Performance Günden
142 for(int i=0; i<columns.size(); i++){
143             if( columns.get(i).getName().equalsIgnoreCase(name) ) return i;
144         }
145         return -1;
146     }
147
148
149     /**
150      * Returns the Column of a column name.
151      */
152     final Column findColumn(String JavaDoc name){
153         for(int i=0; i<columns.size(); i++){
154             Column column = columns.get(i);
155             if( column.getName().equalsIgnoreCase(name) ) return column;
156         }
157         return null;
158     }
159
160
161     
162     /**
163      * Close it and free all resources.
164      */
165     void close() throws Exception JavaDoc{/* in this abstract class is nothing to free */}
166
167 }
168
169
170
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