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| 1 | /* | ||
| 2 | * Copyright (c) 2003, 2004, Oracle and/or its affiliates. All rights reserved. | ||
| 3 | * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. | ||
| 4 | * | ||
| 5 | * This code is free software; you can redistribute it and/or modify it | ||
| 6 | * under the terms of the GNU General Public License version 2 only, as | ||
| 7 | * published by the Free Software Foundation. Oracle designates this | ||
| 8 | * particular file as subject to the "Classpath" exception as provided | ||
| 9 | * by Oracle in the LICENSE file that accompanied this code. | ||
| 10 | * | ||
| 11 | * This code is distributed in the hope that it will be useful, but WITHOUT | ||
| 12 | * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or | ||
| 13 | * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | ||
| 14 | * version 2 for more details (a copy is included in the LICENSE file that | ||
| 15 | * accompanied this code). | ||
| 16 | * | ||
| 17 | * You should have received a copy of the GNU General Public License version | ||
| 18 | * 2 along with this work; if not, write to the Free Software Foundation, | ||
| 19 | * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. | ||
| 20 | * | ||
| 21 | * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA | ||
| 22 | * or visit www.oracle.com if you need additional information or have any | ||
| 23 | * questions. | ||
| 24 | */ | ||
| 25 | |||
| 26 | package javax.sql.rowset.spi; | ||
| 27 | |||
| 28 | import javax.sql.RowSet; | ||
| 29 | import java.sql.SQLException; | ||
| 30 | |||
| 31 | /** | ||
| 32 | * Defines a framework that allows applications to use a manual decision tree | ||
| 33 | * to decide what should be done when a synchronization conflict occurs. | ||
| 34 | * Although it is not mandatory for | ||
| 35 | * applications to resolve synchronization conflicts manually, this | ||
| 36 | * framework provides the means to delegate to the application when conflicts | ||
| 37 | * arise. | ||
| 38 | * <p> | ||
| 39 | * Note that a conflict is a situation where the <code>RowSet</code> object's original | ||
| 40 | * values for a row do not match the values in the data source, which indicates that | ||
| 41 | * the data source row has been modified since the last synchronization. Note also that | ||
| 42 | * a <code>RowSet</code> object's original values are the values it had just prior to the | ||
| 43 | * the last synchronization, which are not necessarily its initial values. | ||
| 44 | * <p> | ||
| 45 | * | ||
| 46 | * <H2>Description of a <code>SyncResolver</code> Object</H2> | ||
| 47 | * | ||
| 48 | * A <code>SyncResolver</code> object is a specialized <code>RowSet</code> object | ||
| 49 | * that implements the <code>SyncResolver</code> interface. | ||
| 50 | * It <b>may</b> operate as either a connected <code>RowSet</code> object (an | ||
| 51 | * implementation of the <code>JdbcRowSet</code> interface) or a connected | ||
| 52 | * <code>RowSet</code> object (an implementation of the | ||
| 53 | * <code>CachedRowSet</code> interface or one of its subinterfaces). For information | ||
| 54 | * on the subinterfaces, see the | ||
| 55 | * <a href="../package-summary.html"><code>javax.sql.rowset</code></a> package | ||
| 56 | * description. The reference implementation for <code>SyncResolver</code> implements | ||
| 57 | * the <code>CachedRowSet</code> interface, but other implementations | ||
| 58 | * may choose to implement the <code>JdbcRowSet</code> interface to satisfy | ||
| 59 | * particular needs. | ||
| 60 | * <P> | ||
| 61 | * After an application has attempted to synchronize a <code>RowSet</code> object with | ||
| 62 | * the data source (by calling the <code>CachedRowSet</code> | ||
| 63 | * method <code>acceptChanges</code>), and one or more conflicts have been found, | ||
| 64 | * a rowset's <code>SyncProvider</code> object creates an instance of | ||
| 65 | * <code>SyncResolver</code>. This new <code>SyncResolver</code> object has | ||
| 66 | * the same number of rows and columns as the | ||
| 67 | * <code>RowSet</code> object that was attempting the synchronization. The | ||
| 68 | * <code>SyncResolver</code> object contains the values from the data source that caused | ||
| 69 | * the conflict(s) and <code>null</code> for all other values. | ||
| 70 | * In addition, it contains information about each conflict. | ||
| 71 | * <P> | ||
| 72 | * | ||
| 73 | * <H2>Getting and Using a <code>SyncResolver</code> Object</H2> | ||
| 74 | * | ||
| 75 | * When the method <code>acceptChanges</code> encounters conflicts, the | ||
| 76 | * <code>SyncProvider</code> object creates a <code>SyncProviderException</code> | ||
| 77 | * object and sets it with the new <code>SyncResolver</code> object. The method | ||
| 78 | * <code>acceptChanges</code> will throw this exception, which | ||
| 79 | * the application can then catch and use to retrieve the | ||
| 80 | * <code>SyncResolver</code> object it contains. The following code snippet uses the | ||
| 81 | * <code>SyncProviderException</code> method <code>getSyncResolver</code> to get | ||
| 82 | * the <code>SyncResolver</code> object <i>resolver</i>. | ||
| 83 | * <PRE> | ||
| 84 | * } catch (SyncProviderException spe) { | ||
| 85 | * SyncResolver resolver = spe.getSyncResolver(); | ||
| 86 | * ... | ||
| 87 | * } | ||
| 88 | * </PRE> | ||
| 89 | * <P> | ||
| 90 | * With <i>resolver</i> in hand, an application can use it to get the information | ||
| 91 | * it contains about the conflict or conflicts. A <code>SyncResolver</code> object | ||
| 92 | * such as <i>resolver</i> keeps | ||
| 93 | * track of the conflicts for each row in which there is a conflict. It also places a | ||
| 94 | * lock on the table or tables affected by the rowset's command so that no more | ||
| 95 | * conflicts can occur while the current conflicts are being resolved. | ||
| 96 | * <P> | ||
| 97 | * The following kinds of information can be obtained from a <code>SyncResolver</code> | ||
| 98 | * object: | ||
| 99 | * <P> | ||
| 100 | * <LI>What operation was being attempted when a conflict occurred<BR> | ||
| 101 | * The <code>SyncProvider</code> interface defines four constants | ||
| 102 | * describing states that may occur. Three | ||
| 103 | * constants describe the type of operation (update, delete, or insert) that a | ||
| 104 | * <code>RowSet</code> object was attempting to perform when a conflict was discovered, | ||
| 105 | * and the fourth indicates that there is no conflict. | ||
| 106 | * These constants are the possible return values when a <code>SyncResolver</code> object | ||
| 107 | * calls the method <code>getStatus</code>. | ||
| 108 | * <PRE> | ||
| 109 | * int operation = resolver.getStatus(); | ||
| 110 | * </PRE> | ||
| 111 | * <P> | ||
| 112 | * <LI>The value in the data source that caused a conflict<BR> | ||
| 113 | * A conflict exists when a value that a <code>RowSet</code> object has changed | ||
| 114 | * and is attempting to write to the data source | ||
| 115 | * has also been changed in the data source since the last synchronization. An | ||
| 116 | * application can call the <code>SyncResolver</code> method | ||
| 117 | * <code>getConflictValue</code > to retrieve the | ||
| 118 | * value in the data source that is the cause of the conflict because the values in a | ||
| 119 | * <code>SyncResolver</code> object are the conflict values from the data source. | ||
| 120 | * <PRE> | ||
| 121 | * java.lang.Object conflictValue = resolver.getConflictValue(2); | ||
| 122 | * </PRE> | ||
| 123 | * Note that the column in <i>resolver</i> can be designated by the column number, | ||
| 124 | * as is done in the preceding line of code, or by the column name. | ||
| 125 | * </UL> | ||
| 126 | * <P> | ||
| 127 | * With the information retrieved from the methods <code>getStatus</code> and | ||
| 128 | * <code>getConflictValue</code>, the application may make a determination as to | ||
| 129 | * which value should be persisted in the data source. The application then calls the | ||
| 130 | * <code>SyncResolver</code> method <code>setResolvedValue</code>, which sets the value | ||
| 131 | * to be persisted in the <code>RowSet</code> object and also in the data source. | ||
| 132 | * <PRE> | ||
| 133 | * resolver.setResolvedValue("DEPT", 8390426); | ||
| 134 | * </PRE> | ||
| 135 | * In the preceding line of code, | ||
| 136 | * the column name designates the column in the <code>RowSet</code> object | ||
| 137 | * that is to be set with the given value. The column number can also be used to | ||
| 138 | * designate the column. | ||
| 139 | * <P> | ||
| 140 | * An application calls the method <code>setResolvedValue</code> after it has | ||
| 141 | * resolved all of the conflicts in the current conflict row and repeats this process | ||
| 142 | * for each conflict row in the <code>SyncResolver</code> object. | ||
| 143 | * <P> | ||
| 144 | * | ||
| 145 | * <H2>Navigating a <code>SyncResolver</code> Object</H2> | ||
| 146 | * | ||
| 147 | * Because a <code>SyncResolver</code> object is a <code>RowSet</code> object, an | ||
| 148 | * application can use all of the <code>RowSet</code> methods for moving the cursor | ||
| 149 | * to navigate a <code>SyncResolver</code> object. For example, an application can | ||
| 150 | * use the <code>RowSet</code> method <code>next</code> to get to each row and then | ||
| 151 | * call the <code>SyncResolver</code> method <code>getStatus</code> to see if the row | ||
| 152 | * contains a conflict. In a row with one or more conflicts, the application can | ||
| 153 | * iterate through the columns to find any non-null values, which will be the values | ||
| 154 | * from the data source that are in conflict. | ||
| 155 | * <P> | ||
| 156 | * To make it easier to navigate a <code>SyncResolver</code> object, especially when | ||
| 157 | * there are large numbers of rows with no conflicts, the <code>SyncResolver</code> | ||
| 158 | * interface defines the methods <code>nextConflict</code> and | ||
| 159 | * <code>previousConflict</code>, which move only to rows | ||
| 160 | * that contain at least one conflict value. Then an application can call the | ||
| 161 | * <code>SyncResolver</code> method <code>getConflictValue</code>, supplying it | ||
| 162 | * with the column number, to get the conflict value itself. The code fragment in the | ||
| 163 | * next section gives an example. | ||
| 164 | * | ||
| 165 | * <H2>Code Example</H2> | ||
| 166 | * | ||
| 167 | * The following code fragment demonstrates how a disconnected <code>RowSet</code> | ||
| 168 | * object <i>crs</i> might attempt to synchronize itself with the | ||
| 169 | * underlying data source and then resolve the conflicts. In the <code>try</code> | ||
| 170 | * block, <i>crs</i> calls the method <code>acceptChanges</code>, passing it the | ||
| 171 | * <code>Connection</code> object <i>con</i>. If there are no conflicts, the | ||
| 172 | * changes in <i>crs</i> are simply written to the data source. However, if there | ||
| 173 | * is a conflict, the method <code>acceptChanges</code> throws a | ||
| 174 | * <code>SyncProviderException</code> object, and the | ||
| 175 | * <code>catch</code> block takes effect. In this example, which | ||
| 176 | * illustrates one of the many ways a <code>SyncResolver</code> object can be used, | ||
| 177 | * the <code>SyncResolver</code> method <code>nextConflict</code> is used in a | ||
| 178 | * <code>while</code> loop. The loop will end when <code>nextConflict</code> returns | ||
| 179 | * <code>false</code>, which will occur when there are no more conflict rows in the | ||
| 180 | * <code>SyncResolver</code> object <i>resolver</i>. In This particular code fragment, | ||
| 181 | * <i>resolver</i> looks for rows that have update conflicts (rows with the status | ||
| 182 | * <code>SyncResolver.UPDATE_ROW_CONFLICT</code>), and the rest of this code fragment | ||
| 183 | * executes only for rows where conflicts occurred because <i>crs</i> was attempting an | ||
| 184 | * update. | ||
| 185 | * <P> | ||
| 186 | * After the cursor for <i>resolver</i> has moved to the next conflict row that | ||
| 187 | * has an update conflict, the method <code>getRow</code> indicates the number of the | ||
| 188 | * current row, and | ||
| 189 | * the cursor for the <code>CachedRowSet</code> object <i>crs</i> is moved to | ||
| 190 | * the comparable row in <i>crs</i>. By iterating | ||
| 191 | * through the columns of that row in both <i>resolver</i> and <i>crs</i>, the conflicting | ||
| 192 | * values can be retrieved and compared to decide which one should be persisted. In this | ||
| 193 | * code fragment, the value in <i>crs</i> is the one set as the resolved value, which means | ||
| 194 | * that it will be used to overwrite the conflict value in the data source. | ||
| 195 | * | ||
| 196 | * <PRE> | ||
| 197 | * try { | ||
| 198 | * | ||
| 199 | * crs.acceptChanges(con); | ||
| 200 | * | ||
| 201 | * } catch (SyncProviderException spe) { | ||
| 202 | * | ||
| 203 | * SyncResolver resolver = spe.getSyncResolver(); | ||
| 204 | * | ||
| 205 | * Object crsValue; // value in the <code>RowSet</code> object | ||
| 206 | * Object resolverValue: // value in the <code>SyncResolver</code> object | ||
| 207 | * Object resolvedValue: // value to be persisted | ||
| 208 | * | ||
| 209 | * while(resolver.nextConflict()) { | ||
| 210 | * if(resolver.getStatus() == SyncResolver.UPDATE_ROW_CONFLICT) { | ||
| 211 | * int row = resolver.getRow(); | ||
| 212 | * crs.absolute(row); | ||
| 213 | * | ||
| 214 | * int colCount = crs.getMetaData().getColumnCount(); | ||
| 215 | * for(int j = 1; j <= colCount; j++) { | ||
| 216 | * if (resolver.getConflictValue(j) != null) { | ||
| 217 | * crsValue = crs.getObject(j); | ||
| 218 | * resolverValue = resolver.getConflictValue(j); | ||
| 219 | * . . . | ||
| 220 | * // compare crsValue and resolverValue to determine | ||
| 221 | * // which should be the resolved value (the value to persist) | ||
| 222 | * resolvedValue = crsValue; | ||
| 223 | * | ||
| 224 | * resolver.setResolvedValue(j, resolvedValue); | ||
| 225 | * } | ||
| 226 | * } | ||
| 227 | * } | ||
| 228 | * } | ||
| 229 | * } | ||
| 230 | * </PRE> | ||
| 231 | * @author Jonathan Bruce | ||
| 232 | */ | ||
| 233 | |||
| 234 | public interface SyncResolver extends RowSet { | ||
| 235 | /** | ||
| 236 | * Indicates that a conflict occurred while the <code>RowSet</code> object was | ||
| 237 | * attempting to update a row in the data source. | ||
| 238 | * The values in the data source row to be updated differ from the | ||
| 239 | * <code>RowSet</code> object's original values for that row, which means that | ||
| 240 | * the row in the data source has been updated or deleted since the last | ||
| 241 | * synchronization. | ||
| 242 | */ | ||
| 243 | public static int UPDATE_ROW_CONFLICT = 0; | ||
| 244 | |||
| 245 | /** | ||
| 246 | * Indicates that a conflict occurred while the <code>RowSet</code> object was | ||
| 247 | * attempting to delete a row in the data source. | ||
| 248 | * The values in the data source row to be updated differ from the | ||
| 249 | * <code>RowSet</code> object's original values for that row, which means that | ||
| 250 | * the row in the data source has been updated or deleted since the last | ||
| 251 | * synchronization. | ||
| 252 | */ | ||
| 253 | public static int DELETE_ROW_CONFLICT = 1; | ||
| 254 | |||
| 255 | /** | ||
| 256 | * Indicates that a conflict occurred while the <code>RowSet</code> object was | ||
| 257 | * attempting to insert a row into the data source. This means that a | ||
| 258 | * row with the same primary key as the row to be inserted has been inserted | ||
| 259 | * into the data source since the last synchronization. | ||
| 260 | */ | ||
| 261 | public static int INSERT_ROW_CONFLICT = 2; | ||
| 262 | |||
| 263 | /** | ||
| 264 | * Indicates that <b>no</b> conflict occured while the <code>RowSet</code> object | ||
| 265 | * was attempting to update, delete or insert a row in the data source. The values in | ||
| 266 | * the <code>SyncResolver</code> will contain <code>null</code> values only as an indication | ||
| 267 | * that no information in pertitent to the conflict resolution in this row. | ||
| 268 | */ | ||
| 269 | public static int NO_ROW_CONFLICT = 3; | ||
| 270 | |||
| 271 | /** | ||
| 272 | * Retrieves the conflict status of the current row of this <code>SyncResolver</code>, | ||
| 273 | * which indicates the operation | ||
| 274 | * the <code>RowSet</code> object was attempting when the conflict occurred. | ||
| 275 | * | ||
| 276 | * @return one of the following constants: | ||
| 277 | * <code>SyncResolver.UPDATE_ROW_CONFLICT</code>, | ||
| 278 | * <code>SyncResolver.DELETE_ROW_CONFLICT</code>, | ||
| 279 | * <code>SyncResolver.INSERT_ROW_CONFLICT</code>, or | ||
| 280 | * <code>SyncResolver.NO_ROW_CONFLICT</code> | ||
| 281 | */ | ||
| 282 | public int getStatus(); | ||
| 283 | |||
| 284 | /** | ||
| 285 | * Retrieves the value in the designated column in the current row of this | ||
| 286 | * <code>SyncResolver</code> object, which is the value in the data source | ||
| 287 | * that caused a conflict. | ||
| 288 | * | ||
| 289 | * @param index an <code>int</code> designating the column in this row of this | ||
| 290 | * <code>SyncResolver</code> object from which to retrieve the value | ||
| 291 | * causing a conflict | ||
| 292 | * @return the value of the designated column in the current row of this | ||
| 293 | * <code>SyncResolver</code> object | ||
| 294 | * @throws SQLException if a database access error occurs | ||
| 295 | */ | ||
| 296 | public Object getConflictValue(int index) throws SQLException; | ||
| 297 | |||
| 298 | /** | ||
| 299 | * Retrieves the value in the designated column in the current row of this | ||
| 300 | * <code>SyncResolver</code> object, which is the value in the data source | ||
| 301 | * that caused a conflict. | ||
| 302 | * | ||
| 303 | * @param columnName a <code>String</code> object designating the column in this row of this | ||
| 304 | * <code>SyncResolver</code> object from which to retrieve the value | ||
| 305 | * causing a conflict | ||
| 306 | * @return the value of the designated column in the current row of this | ||
| 307 | * <code>SyncResolver</code> object | ||
| 308 | * @throws SQLException if a database access error occurs | ||
| 309 | */ | ||
| 310 | public Object getConflictValue(String columnName) throws SQLException; | ||
| 311 | |||
| 312 | /** | ||
| 313 | * Sets <i>obj</i> as the value in column <i>index</i> in the current row of the | ||
| 314 | * <code>RowSet</code> object that is being synchronized. <i>obj</i> | ||
| 315 | * is set as the value in the data source internally. | ||
| 316 | * | ||
| 317 | * @param index an <code>int</code> giving the number of the column into which to | ||
| 318 | * set the value to be persisted | ||
| 319 | * @param obj an <code>Object</code> that is the value to be set in the | ||
| 320 | * <code>RowSet</code> object and persisted in the data source | ||
| 321 | * @throws SQLException if a database access error occurs | ||
| 322 | */ | ||
| 323 | public void setResolvedValue(int index, Object obj) throws SQLException; | ||
| 324 | |||
| 325 | /** | ||
| 326 | * Sets <i>obj</i> as the value in column <i>columnName</i> in the current row of the | ||
| 327 | * <code>RowSet</code> object that is being synchronized. <i>obj</i> | ||
| 328 | * is set as the value in the data source internally. | ||
| 329 | * | ||
| 330 | * @param columnName a <code>String</code> object giving the name of the column | ||
| 331 | * into which to set the value to be persisted | ||
| 332 | * @param obj an <code>Object</code> that is the value to be set in the | ||
| 333 | * <code>RowSet</code> object and persisted in the data source | ||
| 334 | * @throws SQLException if a database access error occurs | ||
| 335 | */ | ||
| 336 | public void setResolvedValue(String columnName, Object obj) throws SQLException; | ||
| 337 | |||
| 338 | /** | ||
| 339 | * Moves the cursor down from its current position to the next row that contains | ||
| 340 | * a conflict value. A <code>SyncResolver</code> object's | ||
| 341 | * cursor is initially positioned before the first conflict row; the first call to the | ||
| 342 | * method <code>nextConflict</code> makes the first conflict row the current row; | ||
| 343 | * the second call makes the second conflict row the current row, and so on. | ||
| 344 | * <p> | ||
| 345 | * A call to the method <code>nextConflict</code> will implicitly close | ||
| 346 | * an input stream if one is open and will clear the <code>SyncResolver</code> | ||
| 347 | * object's warning chain. | ||
| 348 | * | ||
| 349 | * @return <code>true</code> if the new current row is valid; <code>false</code> | ||
| 350 | * if there are no more rows | ||
| 351 | * @throws SQLException if a database access error occurs or the result set type | ||
| 352 | * is <code>TYPE_FORWARD_ONLY</code> | ||
| 353 | * | ||
| 354 | */ | ||
| 355 | public boolean nextConflict() throws SQLException; | ||
| 356 | |||
| 357 | /** | ||
| 358 | * Moves the cursor up from its current position to the previous conflict | ||
| 359 | * row in this <code>SyncResolver</code> object. | ||
| 360 | * <p> | ||
| 361 | * A call to the method <code>previousConflict</code> will implicitly close | ||
| 362 | * an input stream if one is open and will clear the <code>SyncResolver</code> | ||
| 363 | * object's warning chain. | ||
| 364 | * | ||
| 365 | * @return <code>true</code> if the cursor is on a valid row; <code>false</code> | ||
| 366 | * if it is off the result set | ||
| 367 | * @throws SQLException if a database access error occurs or the result set type | ||
| 368 | * is <code>TYPE_FORWARD_ONLY</code> | ||
| 369 | */ | ||
| 370 | public boolean previousConflict() throws SQLException; | ||
| 371 | |||
| 372 | } | ||