1 /*
2 * #%L
3 * Bitrepository Service
4 * %%
5 * Copyright (C) 2010 - 2013 The State and University Library, The Royal Library and The State Archives, Denmark
6 * %%
7 * This program is free software: you can redistribute it and/or modify
8 * it under the terms of the GNU Lesser General Public License as
9 * published by the Free Software Foundation, either version 2.1 of the
10 * License, or (at your option) any later version.
11 *
12 * This program is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 * GNU General Lesser Public License for more details.
16 *
17 * You should have received a copy of the GNU General Lesser Public
18 * License along with this program. If not, see
19 * <http://www.gnu.org/licenses/lgpl-2.1.html>.
20 * #L%
21 */
22 package org.bitrepository.service.database;
23
24 import java.sql.Connection;
25 import java.sql.PreparedStatement;
26 import java.sql.ResultSet;
27 import java.sql.SQLException;
28 import java.util.HashMap;
29 import java.util.Map;
30
31 /**
32 * Abstract class for migrating the databases.
33 * Handles the default operations.
34 *
35 * It is asserted, that the database has the following table for the versions:
36 *
37 * create table tableversions (
38 * tablename varchar(100) not null, -- Name of table
39 * version int not null -- version of table
40 * );
41 */
42 public abstract class DatabaseMigrator extends DatabaseMaintainer {
43 /** The connection to the database.*/
44 protected final DBConnector connector;
45
46 /** The name of the "table versions" table.*/
47 protected static final String TABLEVERSIONS_TABLE = "tableversions";
48 /** The 'tablename' coloumn in the table.*/
49 protected static final String TV_TABLENAME = "tablename";
50 /** The 'version' coloumn in the table.*/
51 protected static final String TV_VERSION = "version";
52
53 /**
54 * Constructor.
55 * @param connector The connector for the database.
56 */
57 protected DatabaseMigrator(DBConnector connector) {
58 this.connector = connector;
59 }
60
61 /**
62 * Extracts the version numbers for the tables in the database.
63 * @return The mapping between the table names and their respective version number.
64 */
65 protected Map<String, Integer> getTableVersions() {
66 Map<String, Integer> resultMap = new HashMap<String, Integer>();
67
68 // Extract the table name as first coloumn and version as second coloumn.
69 String sql = "SELECT " + TV_TABLENAME + " , " + TV_VERSION + " FROM " + TABLEVERSIONS_TABLE;
70 int tablenameColoumn = 1;
71 int versionColoumn = 2;
72
73 try {
74 PreparedStatement ps = null;
75 ResultSet res = null;
76 Connection conn = null;
77 try {
78 conn = connector.getConnection();
79 ps = DatabaseUtils.createPreparedStatement(conn, sql, new Object[0]);
80 res = ps.executeQuery();
81
82 while (res.next()) {
83 resultMap.put(res.getString(tablenameColoumn), res.getInt(versionColoumn));
84 }
85 } finally {
86 if(res != null) {
87 res.close();
88 }
89 if(ps != null) {
90 ps.close();
91 }
92 if(conn != null) {
93 conn.close();
94 }
95 }
96 } catch (SQLException e) {
97 throw new IllegalStateException("Cannot extract the table versions.", e);
98 }
99
100 return resultMap;
101 }
102
103 /**
104 * Performs the update of a single table.
105 * @param tablename The name of the table to update.
106 * @param newVersion The new version for the table.
107 * @param updateSql The SQL for updating the table.
108 * @param args The arguments for performing this update.
109 */
110 protected void updateTable(String tablename, Integer newVersion, String updateSql, Object ... args) {
111 String migrateSql = "UPDATE " + TABLEVERSIONS_TABLE + " SET " + TV_VERSION + " = ? WHERE " + TV_TABLENAME
112 + " = ?";
113
114 DatabaseUtils.executeStatement(connector, updateSql, args);
115 DatabaseUtils.executeStatement(connector, migrateSql, newVersion, tablename);
116 }
117
118 /**
119 * Method for running a specific migrate script on the embedded database.
120 * Will throw an exception if the migration is tried to be performed on another type of database.
121 * @param migrateScriptName The name of the migrate script to run.
122 */
123 protected void migrateDerbyDatabase(String migrateScriptName) {
124 if(connector.getDatabaseDriverClass().equals(DatabaseUtils.DERBY_EMBEDDED_DRIVER)) {
125 try {
126 runScript(connector, migrateScriptName);
127 } catch (Exception e) {
128 throw new IllegalStateException("Cannot migrate the database with the script '" + migrateScriptName
129 + "'. It is very possible that the database has to be migrated by manually running "
130 + "migrate-scripts.", e);
131 }
132 } else {
133 throw new IllegalStateException("Can only perform database migrations on embedded derby databases. "
134 + "Migration of other databases must be performed manually. Your database had the drivers: "
135 + connector.getDatabaseDriverClass());
136 }
137 }
138
139 /**
140 * Perform the migration for the given database.
141 */
142 abstract public void migrate();
143
144 /**
145 * Method to determine if migration is needed.
146 * @return true if migration is needed, false otherwise.
147 */
148 public abstract boolean needsMigration();
149
150 }