- /*
- * @(#)SyncResolver.java 1.4 04/02/27
- *
- * Copyright 2004 Sun Microsystems, Inc. All rights reserved.
- * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
- */
-
- 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;
-
- }