Back to index...

	/*
	* Copyright (c) 2003, 2013, 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.
	*
	*
	* <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.
	*
	*
	* <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>
	* {@code
	* } 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:
	*
	* <h3>What operation was being attempted when a conflict occurred</h3>
	* 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>
	* {@code int operation = resolver.getStatus(); }
	* </PRE>
	*
	* <h3>The value in the data source that caused a conflict</h3>
	* 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.
	* <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.
	*
	*
	* <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>
	* {@code
	* try {
	*
	* crs.acceptChanges(con);
	*
	* } catch (SyncProviderException spe) {
	*
	* SyncResolver resolver = spe.getSyncResolver();
	*
	* Object crsValue; // value in the RowSet object
	* Object resolverValue: // value in the SyncResolver 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
	* @since 1.5
	*/

	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 occurred 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 pertinent 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;

	}

Back to index...