1 package org.apache.torque.adapter;
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57 import java.util.Date;
58 import java.io.Serializable;
59 import java.sql.Connection;
60 import java.sql.SQLException;
61 import java.sql.Timestamp;
62
63 /***
64 * <code>DB</code> defines the interface for a Torque database
65 * adapter. Support for new databases is added by subclassing
66 * <code>DB</code> and implementing its abstract interface, and by
67 * registering the new database adapter and its corresponding
68 * JDBC driver in the service configuration file.
69 *
70 * <p>The Torque database adapters exist to present a uniform
71 * interface to database access across all available databases. Once
72 * the necessary adapters have been written and configured,
73 * transparent swapping of databases is theoretically supported with
74 * <i>zero code changes</i> and minimal configuration file
75 * modifications.
76 *
77 * <p>Torque uses the driver class name to find the right adapter.
78 * A JDBC driver corresponding to your adapter must be added to the properties
79 * file, using the fully-qualified class name of the driver. If no driver is
80 * specified for your database, <code>driver.default</code> is used.
81 *
82 * <pre>
83 * #### MySQL MM Driver
84 * database.default.driver=org.gjt.mm.mysql.Driver
85 * database.default.url=jdbc:mysql://localhost/DATABASENAME
86 * </pre>
87 *
88 * @author <a href="mailto:jon@latchkey.com">Jon S. Stevens</a>
89 * @author <a href="mailto:bmclaugh@algx.net">Brett McLaughlin</a>
90 * @author <a href="mailto:dlr@finemaltcoding.com">Daniel Rall</a>
91 * @version $Id: DB.java,v 1.31 2003/01/08 16:43:57 henning Exp $
92 */
93 public abstract class DB implements Serializable, IDMethod
94 {
95 /*** Database does not support limiting result sets. */
96 public static final int LIMIT_STYLE_NONE = 0;
97
98 /*** <code>SELECT ... LIMIT <limit>, [<offset>]</code> */
99 public static final int LIMIT_STYLE_POSTGRES = 1;
100
101 /*** <code>SELECT ... LIMIT [<offset>, ] <offset></code> */
102 public static final int LIMIT_STYLE_MYSQL = 2;
103
104 /*** <code>SET ROWCOUNT <offset> SELECT ... SET ROWCOUNT 0</code> */
105 public static final int LIMIT_STYLE_SYBASE = 3;
106
107 /*** <code><pre>SELECT ... WHERE ... AND ROWNUM < <limit></pre></code> */
108 public static final int LIMIT_STYLE_ORACLE = 4;
109
110 /***
111 * Empty constructor.
112 */
113 protected DB()
114 {
115 }
116
117 /***
118 * This method is used to ignore case.
119 *
120 * @param in The string to transform to upper case.
121 * @return The upper case string.
122 */
123 public abstract String toUpperCase(String in);
124
125 /***
126 * Returns the character used to indicate the beginning and end of
127 * a piece of text used in a SQL statement (generally a single
128 * quote).
129 *
130 * @return The text delimeter.
131 */
132 public char getStringDelimiter()
133 {
134 return '\'';
135 }
136
137 /***
138 * Returns the constant from the {@link
139 * org.apache.torque.adapter.IDMethod} interface denoting which
140 * type of primary key generation method this type of RDBMS uses.
141 *
142 * @return IDMethod constant
143 */
144 public abstract String getIDMethodType();
145
146 /***
147 * Returns SQL used to get the most recently inserted primary key.
148 * Databases which have no support for this return
149 * <code>null</code>.
150 *
151 * @param obj Information used for key generation.
152 * @return The most recently inserted database key.
153 */
154 public abstract String getIDMethodSQL(Object obj);
155
156 /***
157 * Locks the specified table.
158 *
159 * @param con The JDBC connection to use.
160 * @param table The name of the table to lock.
161 * @throws SQLException No Statement could be created or executed.
162 */
163 public abstract void lockTable(Connection con, String table)
164 throws SQLException;
165
166 /***
167 * Unlocks the specified table.
168 *
169 * @param con The JDBC connection to use.
170 * @param table The name of the table to unlock.
171 * @throws SQLException No Statement could be created or executed.
172 */
173 public abstract void unlockTable(Connection con, String table)
174 throws SQLException;
175
176 /***
177 * This method is used to ignore case.
178 *
179 * @param in The string whose case to ignore.
180 * @return The string in a case that can be ignored.
181 */
182 public abstract String ignoreCase(String in);
183
184 /***
185 * This method is used to ignore case in an ORDER BY clause.
186 * Usually it is the same as ignoreCase, but some databases
187 * (Interbase for example) does not use the same SQL in ORDER BY
188 * and other clauses.
189 *
190 * @param in The string whose case to ignore.
191 * @return The string in a case that can be ignored.
192 */
193 public String ignoreCaseInOrderBy(String in)
194 {
195 return ignoreCase(in);
196 }
197
198 /***
199 * This method is used to check whether the database natively
200 * supports limiting the size of the resultset.
201 *
202 * @return True if the database natively supports limiting the
203 * size of the resultset.
204 */
205 public boolean supportsNativeLimit()
206 {
207 return false;
208 }
209
210 /***
211 * This method is used to check whether the database natively
212 * supports returning results starting at an offset position other
213 * than 0.
214 *
215 * @return True if the database natively supports returning
216 * results starting at an offset position other than 0.
217 */
218 public boolean supportsNativeOffset()
219 {
220 return false;
221 }
222
223 /***
224 * This method is for the SqlExpression.quoteAndEscape rules. The rule is,
225 * any string in a SqlExpression with a BACKSLASH will either be changed to
226 * "//" or left as "\". SapDB does not need the escape character.
227 *
228 * @return true if the database needs to escape text in SqlExpressions.
229 */
230
231 public boolean escapeText()
232 {
233 return true;
234 }
235
236 /***
237 * This method is used to check whether the database supports
238 * limiting the size of the resultset.
239 *
240 * @return The limit style for the database.
241 */
242 public int getLimitStyle()
243 {
244 return LIMIT_STYLE_NONE;
245 }
246
247 /***
248 * This method is used to format any date string.
249 * Database can use different default date formats.
250 *
251 * @param date the Date to format
252 * @return The proper date formatted String.
253 */
254 public String getDateString(Date date)
255 {
256 Timestamp ts = null;
257 if (date instanceof Timestamp)
258 {
259 ts = (Timestamp) date;
260 }
261 else
262 {
263 ts = new Timestamp(date.getTime());
264 }
265
266 return ("{ts '" + ts + "'}");
267 }
268
269 /***
270 * This method is used to format a boolean string.
271 *
272 * @param b the Boolean to format
273 * @return The proper date formatted String.
274 */
275 public String getBooleanString(Boolean b)
276 {
277 return (Boolean.TRUE.equals(b) ? "1" : "0");
278 }
279 }