| /* |
| * 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 |
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| * 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 |
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| * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
| * |
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| |
| 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; |
| |
| } |