/* * Copyright (c) 2003, 2004, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation.  Oracle designates this * particular file as subject to the "Classpath" exception as provided * by Oracle in the LICENSE file that accompanied this code. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */ package javax.sql.rowset.spi; import javax.sql.RowSet;import java.sql.SQLException; /** * Defines a framework that allows applications to use a manual decision tree * to decide what should be done when a synchronization conflict occurs. * Although it is not mandatory for * applications to resolve synchronization conflicts manually, this * framework provides the means to delegate to the application when conflicts * arise. * <p> * Note that a conflict is a situation where the <code>RowSet</code> object's original * values for a row do not match the values in the data source, which indicates that * the data source row has been modified since the last synchronization. Note also that * a <code>RowSet</code> object's original values are the values it had just prior to the * the last synchronization, which are not necessarily its initial values. * <p> * * <H2>Description of a <code>SyncResolver</code> Object</H2> * * A <code>SyncResolver</code> object is a specialized <code>RowSet</code> object * that implements the <code>SyncResolver</code> interface. * It <b>may</b> operate as either a connected <code>RowSet</code> object (an * implementation of the <code>JdbcRowSet</code> interface) or a connected * <code>RowSet</code> object (an implementation of the * <code>CachedRowSet</code> interface or one of its subinterfaces). For information * on the subinterfaces, see the * <a href="../package-summary.html"><code>javax.sql.rowset</code></a> package * description. The reference implementation for <code>SyncResolver</code> implements * the <code>CachedRowSet</code> interface, but other implementations * may choose to implement the <code>JdbcRowSet</code> interface to satisfy * particular needs. * <P> * After an application has attempted to synchronize a <code>RowSet</code> object with * the data source (by calling the <code>CachedRowSet</code> * method <code>acceptChanges</code>), and one or more conflicts have been found, * a rowset's <code>SyncProvider</code> object creates an instance of * <code>SyncResolver</code>. This new <code>SyncResolver</code> object has * the same number of rows and columns as the * <code>RowSet</code> object that was attempting the synchronization. The * <code>SyncResolver</code> object contains the values from the data source that caused * the conflict(s) and <code>null</code> for all other values. * In addition, it contains information about each conflict. * <P> * * <H2>Getting and Using a <code>SyncResolver</code> Object</H2> * * When the method <code>acceptChanges</code> encounters conflicts, the * <code>SyncProvider</code> object creates a <code>SyncProviderException</code> * object and sets it with the new <code>SyncResolver</code> object. The method * <code>acceptChanges</code> will throw this exception, which * the application can then catch and use to retrieve the * <code>SyncResolver</code> object it contains. The following code snippet uses the * <code>SyncProviderException</code> method <code>getSyncResolver</code> to get * the <code>SyncResolver</code> object <i>resolver</i>. * <PRE> *     } catch (SyncProviderException spe) { *         SyncResolver resolver = spe.getSyncResolver(); *     ... *     } * </PRE> * <P> * With <i>resolver</i> in hand, an application can use it to get the information * it contains about the conflict or conflicts.  A <code>SyncResolver</code> object * such as <i>resolver</i> keeps * track of the conflicts for each row in which there is a conflict.  It also places a * lock on the table or tables affected by the rowset's command so that no more * conflicts can occur while the current conflicts are being resolved. * <P> * The following kinds of information can be obtained from a <code>SyncResolver</code> * object: * <P> *    <LI>What operation was being attempted when a conflict occurred<BR> * The <code>SyncProvider</code> interface defines four constants * describing states that may occur. Three * constants describe the type of operation (update, delete, or insert) that a * <code>RowSet</code> object was attempting to perform when a conflict was discovered, * and the fourth indicates that there is no conflict. * These constants are the possible return values when a <code>SyncResolver</code> object * calls the method <code>getStatus</code>. * <PRE> *     int operation = resolver.getStatus(); * </PRE> * <P> *    <LI>The value in the data source that caused a conflict<BR> * A conflict exists when a value that a <code>RowSet</code> object has changed * and is attempting to write to the data source * has also been changed in the data source since the last synchronization.  An * application can call the <code>SyncResolver</code> method * <code>getConflictValue</code > to retrieve the * value in the data source that is the cause of the conflict because the values in a * <code>SyncResolver</code> object are the conflict values from the data source. * <PRE> *     java.lang.Object conflictValue = resolver.getConflictValue(2); * </PRE> * Note that the column in <i>resolver</i> can be designated by the column number, * as is done in the preceding line of code, or by the column name. * </UL> * <P> * With the information retrieved from the methods <code>getStatus</code> and * <code>getConflictValue</code>, the application may make a determination as to * which value should be persisted in the data source. The application then calls the * <code>SyncResolver</code> method <code>setResolvedValue</code>, which sets the value * to be persisted in the <code>RowSet</code> object and also in the data source. * <PRE> *     resolver.setResolvedValue("DEPT", 8390426); * </PRE> * In the preceding line of code, * the column name designates the column in the <code>RowSet</code> object * that is to be set with the given value. The column number can also be used to * designate the column. * <P> * An application calls the method <code>setResolvedValue</code> after it has * resolved all of the conflicts in the current conflict row and repeats this process * for each conflict row in the <code>SyncResolver</code> object. * <P> * * <H2>Navigating a <code>SyncResolver</code> Object</H2> * * Because a <code>SyncResolver</code> object is a <code>RowSet</code> object, an * application can use all of the <code>RowSet</code> methods for moving the cursor * to navigate a <code>SyncResolver</code> object. For example, an application can * use the <code>RowSet</code> method <code>next</code> to get to each row and then * call the <code>SyncResolver</code> method <code>getStatus</code> to see if the row * contains a conflict.  In a row with one or more conflicts, the application can * iterate through the columns to find any non-null values, which will be the values * from the data source that are in conflict. * <P> * To make it easier to navigate a <code>SyncResolver</code> object, especially when * there are large numbers of rows with no conflicts, the <code>SyncResolver</code> * interface defines the methods <code>nextConflict</code> and * <code>previousConflict</code>, which move only to rows * that contain at least one conflict value. Then an application can call the * <code>SyncResolver</code> method <code>getConflictValue</code>, supplying it * with the column number, to get the conflict value itself. The code fragment in the * next section gives an example. * * <H2>Code Example</H2> * * The following code fragment demonstrates how a disconnected <code>RowSet</code> * object <i>crs</i> might attempt to synchronize itself with the * underlying data source and then resolve the conflicts. In the <code>try</code> * block, <i>crs</i> calls the method <code>acceptChanges</code>, passing it the * <code>Connection</code> object <i>con</i>.  If there are no conflicts, the * changes in <i>crs</i> are simply written to the data source.  However, if there * is a conflict, the method <code>acceptChanges</code> throws a * <code>SyncProviderException</code> object, and the * <code>catch</code> block takes effect.  In this example, which * illustrates one of the many ways a <code>SyncResolver</code> object can be used, * the <code>SyncResolver</code> method <code>nextConflict</code> is used in a * <code>while</code> loop. The loop will end when <code>nextConflict</code> returns * <code>false</code>, which will occur when there are no more conflict rows in the * <code>SyncResolver</code> object <i>resolver</i>. In This particular code fragment, * <i>resolver</i> looks for rows that have update conflicts (rows with the status * <code>SyncResolver.UPDATE_ROW_CONFLICT</code>), and the rest of this code fragment * executes only for rows where conflicts occurred because <i>crs</i> was attempting an * update. * <P> * After the cursor for <i>resolver</i> has moved to the next conflict row that * has an update conflict, the method <code>getRow</code> indicates the number of the * current row, and * the cursor for the <code>CachedRowSet</code> object <i>crs</i> is moved to * the comparable row in <i>crs</i>. By iterating * through the columns of that row in both <i>resolver</i> and <i>crs</i>, the conflicting * values can be retrieved and compared to decide which one should be persisted. In this * code fragment, the value in <i>crs</i> is the one set as the resolved value, which means * that it will be used to overwrite the conflict value in the data source. * * <PRE> *     try { * *         crs.acceptChanges(con); * *     } catch (SyncProviderException spe) { * *         SyncResolver resolver = spe.getSyncResolver(); * *         Object crsValue;  // value in the <code>RowSet</code> object *         Object resolverValue:  // value in the <code>SyncResolver</code> object *         Object resolvedValue:  // value to be persisted * *         while(resolver.nextConflict())  { *             if(resolver.getStatus() == SyncResolver.UPDATE_ROW_CONFLICT)  { *                 int row = resolver.getRow(); *                 crs.absolute(row); * *                 int colCount = crs.getMetaData().getColumnCount(); *                 for(int j = 1; j <= colCount; j++) { *                     if (resolver.getConflictValue(j) != null)  { *                         crsValue = crs.getObject(j); *                         resolverValue = resolver.getConflictValue(j); *                         . . . *                         // compare crsValue and resolverValue to determine *                         // which should be the resolved value (the value to persist) *                         resolvedValue = crsValue; * *                         resolver.setResolvedValue(j, resolvedValue); *                      } *                  } *              } *          } *      } * </PRE> * @author  Jonathan Bruce */ public interface SyncResolver extends RowSet {    /**     * Indicates that a conflict occurred while the <code>RowSet</code> object was     * attempting to update a row in the data source.     * The values in the data source row to be updated differ from the     * <code>RowSet</code> object's original values for that row, which means that     * the row in the data source has been updated or deleted since the last     * synchronization.     */     public static int UPDATE_ROW_CONFLICT = 0;     /**     * Indicates that a conflict occurred while the <code>RowSet</code> object was     * attempting to delete a row in the data source.     * The values in the data source row to be updated differ from the     * <code>RowSet</code> object's original values for that row, which means that     * the row in the data source has been updated or deleted since the last     * synchronization.     */    public static int DELETE_ROW_CONFLICT = 1;    /**    * Indicates that a conflict occurred while the <code>RowSet</code> object was    * attempting to insert a row into the data source.  This means that a    * row with the same primary key as the row to be inserted has been inserted    * into the data source since the last synchronization.    */    public static int INSERT_ROW_CONFLICT = 2;     /**     * Indicates that <b>no</b> conflict occured while the <code>RowSet</code> object     * was attempting to update, delete or insert a row in the data source. The values in     * the <code>SyncResolver</code> will contain <code>null</code> values only as an indication     * that no information in pertitent to the conflict resolution in this row.     */    public static int NO_ROW_CONFLICT = 3;     /**     * Retrieves the conflict status of the current row of this <code>SyncResolver</code>,     * which indicates the operation     * the <code>RowSet</code> object was attempting when the conflict occurred.     *     * @return one of the following constants:     *         <code>SyncResolver.UPDATE_ROW_CONFLICT</code>,     *         <code>SyncResolver.DELETE_ROW_CONFLICT</code>,     *         <code>SyncResolver.INSERT_ROW_CONFLICT</code>, or     *         <code>SyncResolver.NO_ROW_CONFLICT</code>     */    public int getStatus();     /**     * Retrieves the value in the designated column in the current row of this     * <code>SyncResolver</code> object, which is the value in the data source     * that caused a conflict.     *     * @param index an <code>int</code> designating the column in this row of this     *        <code>SyncResolver</code> object from which to retrieve the value     *        causing a conflict     * @return the value of the designated column in the current row of this     *         <code>SyncResolver</code> object     * @throws SQLException if a database access error occurs     */    public Object getConflictValue(int index) throws SQLException;     /**     * Retrieves the value in the designated column in the current row of this     * <code>SyncResolver</code> object, which is the value in the data source     * that caused a conflict.     *     * @param columnName a <code>String</code> object designating the column in this row of this     *        <code>SyncResolver</code> object from which to retrieve the value     *        causing a conflict     * @return the value of the designated column in the current row of this     *         <code>SyncResolver</code> object     * @throws SQLException if a database access error occurs     */    public Object getConflictValue(String columnName) throws SQLException;     /**     * Sets <i>obj</i> as the value in column <i>index</i> in the current row of the     * <code>RowSet</code> object that is being synchronized. <i>obj</i>     * is set as the value in the data source internally.     *     * @param index an <code>int</code> giving the number of the column into which to     *        set the value to be persisted     * @param obj an <code>Object</code> that is the value to be set in the     *        <code>RowSet</code> object and persisted in the data source     * @throws SQLException if a database access error occurs     */    public void setResolvedValue(int index, Object obj) throws SQLException;     /**     * Sets <i>obj</i> as the value in column <i>columnName</i> in the current row of the     * <code>RowSet</code> object that is being synchronized. <i>obj</i>     * is set as the value in the data source internally.     *     * @param columnName a <code>String</code> object giving the name of the column     *        into which to set the value to be persisted     * @param obj an <code>Object</code> that is the value to be set in the     *        <code>RowSet</code> object and persisted in the data source     * @throws SQLException if a database access error occurs     */    public void setResolvedValue(String columnName, Object obj) throws SQLException;     /**     * Moves the cursor down from its current position to the next row that contains     * a conflict value. A <code>SyncResolver</code> object's     * cursor is initially positioned before the first conflict row; the first call to the     * method <code>nextConflict</code> makes the first conflict row the current row;     * the second call makes the second conflict row the current row, and so on.     * <p>     * A call to the method <code>nextConflict</code> will implicitly close     * an input stream if one is open and will clear the <code>SyncResolver</code>     * object's warning chain.     *     * @return <code>true</code> if the new current row is valid; <code>false</code>     *         if there are no more rows     * @throws SQLException if a database access error occurs or the result set type     *     is <code>TYPE_FORWARD_ONLY</code>     *     */    public boolean nextConflict() throws SQLException;     /**     * Moves the cursor up from its current position to the previous conflict     * row in this <code>SyncResolver</code> object.     * <p>     * A call to the method <code>previousConflict</code> will implicitly close     * an input stream if one is open and will clear the <code>SyncResolver</code>     * object's warning chain.     *     * @return <code>true</code> if the cursor is on a valid row; <code>false</code>     *     if it is off the result set     * @throws SQLException if a database access error occurs or the result set type     *     is <code>TYPE_FORWARD_ONLY</code>     */    public boolean previousConflict() throws SQLException; }