syncprovider.java

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/*
 * @(#)SyncProvider.java	1.10 05/11/17
 *
 * Copyright 2006 Sun Microsystems, Inc. All rights reserved.
 * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */

package javax.sql.rowset.spi;

import javax.sql.*;

/**
 * The synchronization mechanism that provides reader/writer capabilities for 
 * disconnected <code>RowSet</code> objects.
 * A <code>SyncProvider</code> implementation is a class that extends the
 * <code>SyncProvider</code> abstract class.
 * <P>
 * A <code>SyncProvider</code> implementation is
 * identified by a unique ID, which is its fully qualified class name.
 * This name must be registered with the 
 * <code>SyncFactory</code> SPI, thus making the implementation available to 
 * all <code>RowSet</code> implementations. 
 * The factory mechanism in the reference implementation uses this name to instantiate
 * the implementation, which can then provide a <code>RowSet</code> object with its
 * reader (a <code>javax.sql.RowSetReader</code> object) and its writer (a
 * <code>javax.sql.RowSetWriter</code> object).
 * <P>
 * The Jdbc <code>RowSet</code> Implementations specification provides two
 * reference implementations of the <code>SyncProvider</code> abstract class: 
 * <code>RIOptimisticProvider</code> and <code>RIXMLProvider</code>. 
 * The <code>RIOptimisticProvider</code> can set any <code>RowSet</code>
 * implementation with a <code>RowSetReader</code> object and a 
 * <code>RowSetWriter</code> object.  However, only the <code>RIXMLProvider</code>
 * implementation can set an <code>XmlReader</code> object and an
 * <code>XmlWriter</code> object. A <code>WebRowSet</code> object uses the
 * <code>XmlReader</code> object to read data in XML format to populate itself with that
 * data.  It uses the <code>XmlWriter</code> object to write itself to a stream or
 * <code>java.io.Writer</code> object in XML format. 
 * <P>
 * <h3>1.0 Naming Convention for Implementations</h3>
 * As a guide  to naming <code>SyncProvider</code>
 * implementations, the following should be noted:
 * <UL>
 * <li>The name for a <code>SyncProvider</code> implementation 
 * is its fully qualified class name.  
 * <li>It is recommended that vendors supply a
 * <code>SyncProvider</code> implementation in a package named <code>providers</code>.
 * </UL>
 * <p>
 * For instance, if a vendor named Fred, Inc. offered a 
 * <code>SyncProvider</code> implementation, you could have the following:
 * <PRE>
 *     Vendor name:  Fred, Inc.     
 *     Domain name of vendor:  com.fred
 *     Package name:  com.fred.providers
 *     SyncProvider implementation class name:  HighAvailabilityProvider
 *
 *     Fully qualified class name of SyncProvider implementation:
 *                        com.fred.providers.HighAvailabilityProvider 
 * </PRE>
 * <P>
 * The following line of code uses the fully qualified name to register
 * this implementation with the <code>SyncFactory</code> static instance.
 * <PRE>
 *     SyncFactory.registerProvider(
 *                          "com.fred.providers.HighAvailabilityProvider");
 * </PRE>
 * <P>
 * The default <code>SyncProvider</code> object provided with the reference 
 * implementation uses the following name:
 * <pre>
 *     com.sun.rowset.providers.RIOptimisticProvider 
 * </pre>
 * <p>
 * A vendor can register a <code>SyncProvider</code> implementation class name 
 * with Sun Microsystems, Inc. by sending email to [e-mail].
 * Sun will maintain a database listing the 
 * available <code>SyncProvider</code> implementations for use with compliant
 * <code>RowSet</code> implementations.  This database will be similar to the
 * one already maintained to list available JDBC drivers.
 * <P>
 * Vendors should refer to the reference implementation synchronization
 * providers for additional guidance on how to implement a new 
 * <code>SyncProvider</code> implementation.
 * 
 * <h3>2.0 How a <code>RowSet</code> Object Gets Its Provider</h3>
 * 
 * A disconnected <code>Rowset</code> object may get access to a 
 * <code>SyncProvider</code> object in one of the following two ways:
 * <UL>
 *  <LI>Using a constructor<BR>
 *      <PRE>
 *       CachedRowSet crs = new CachedRowSet(
 *                  "com.fred.providers.HighAvailabilitySyncProvider"); 
 *      </PRE>
 *  <LI>Using the <code>setSyncProvider</code> method
 *      <PRE>
 *       CachedRowSet crs = new CachedRowSet(); 
 *       crs.setSyncProvider("com.fred.providers.HighAvailabilitySyncProvider"); 
 *      </PRE>

 * </UL>
 * <p> 
 * By default, the reference implementations of the <code>RowSet</code> synchronization
 * providers are always available to the Java platform.
 * If no other pluggable synchronization providers have been correctly
 * registered, the <code>SyncFactory</code> will automatically generate
 * an instance of the default <code>SyncProvider</code> reference implementation.
 * Thus, in the preceding code fragment, if no implementation named
 * <code>com.fred.providers.HighAvailabilitySyncProvider</code> has been
 * registered with the <code>SyncFactory</code> instance, <i>crs</i> will be 
 * assigned the default provider in the reference implementation, which is
 * <code>com.sun.rowset.providers.RIOptimisticProvider</code>. 
 * <p>
 * <h3>3.0 Violations and Synchronization Issues</h3>
 * If an update between a disconnected <code>RowSet</code> object
 * and a data source violates 
 * the original query or the underlying data source constraints, this will 
 * result in undefined behavior for all disconnected <code>RowSet</code> implementations 
 * and their designated <code>SyncProvider</code> implementations. 
 * Not defining the behavior when such violations occur offers greater flexibility 
 * for a <code>SyncProvider</code>
 * implementation to determine its own best course of action.
 * <p>
 * A <code>SyncProvider</code> implementation 
 * may choose to implement a specific handler to
 * handle a subset of query violations.
 * However if an original query violation or a more general data source constraint
 * violation is not handled by the <code>SyncProvider</code> implementation,
 * all <code>SyncProvider</code>
 * objects must throw a <code>SyncProviderException</code>.
 * <p>
 * <h3>4.0 Updatable SQL VIEWs</h3>
 * It is possible for any disconnected or connected <code>RowSet</code> object to be populated 
 * from an SQL query that is formulated originally from an SQL <code>VIEW</code>.
 * While in many cases it is possible for an update to be performed to an
 * underlying view, such an update requires additional metadata, which may vary.
 * The <code>SyncProvider</code> class provides two constants to indicate whether
 * an implementation supports updating an SQL <code>VIEW</code>.
 * <ul>
 * <li><code><b>NONUPDATABLE_VIEW_SYNC</b></code> - Indicates that a <code>SyncProvider</code>
 * implementation does not support synchronization with an SQL <code>VIEW</code> as the
 * underlying source of data for the <code>RowSet</code> object.
 * <li><code><b>UPDATABLE_VIEW_SYNC</b></code> - Indicates that a 
 * <code>SyncProvider</code> implementation 
 * supports synchronization with an SQL <code>VIEW</code> as the underlying source
 * of data.
 * </ul>
 * <P>
 * The default is for a <code>RowSet</code> object not to be updatable if it was
 * populated with data from an SQL <code>VIEW</code>.
 * <P>
 * <h3>5.0 <code>SyncProvider</code> Constants</h3>
 * The <code>SyncProvider</code> class provides three sets of constants that
 * are used as return values or parameters for <code>SyncProvider</code> methods.
 * <code>SyncProvider</code> objects may be implemented to perform synchronization
 * between a <code>RowSet</code> object and its underlying data source with varying
 * degrees of of care. The first group of constants indicate how synchronization
 * is handled. For example, <code>GRADE_NONE</code> indicates that a 
 * <code>SyncProvider</code> object will not take any care to see what data is
 * valid and will simply write the <code>RowSet</code> data to the data source.
 * <code>GRADE_MODIFIED_AT_COMMIT</code> indicates that the provider will check
 * only modified data for validity.  Other grades check all data for validity
 * or set locks when data is modified or loaded.
 * <OL>
 *  <LI>Constants to indicate the synchronization grade of a 
 *     <code>SyncProvider</code> object
 *   <UL>
 *    <LI>SyncProvider.GRADE_NONE
 *    <LI>SyncProvider.GRADE_MODIFIED_AT_COMMIT
 *    <LI>SyncProvider.GRADE_CHECK_ALL_AT_COMMIT
 *    <LI>SyncProvider.GRADE_LOCK_WHEN_MODIFIED
 *    <LI>SyncProvider.GRADE_LOCK_WHEN_LOADED
 *   </UL>
 *  <LI>Constants to indicate what locks are set on the data source
 *   <UL> 
 *     <LI>SyncProvider.DATASOURCE_NO_LOCK
 *     <LI>SyncProvider.DATASOURCE_ROW_LOCK
 *     <LI>SyncProvider.DATASOURCE_TABLE_LOCK
 *     <LI>SyncProvider.DATASOURCE_DB_LOCK
 *   </UL> 
 *  <LI>Constants to indicate whether a <code>SyncProvider</code> object can
 *       perform updates to an SQL <code>VIEW</code> <BR>
 *       These constants are explained in the preceding section (4.0).
 *   <UL>
 *     <LI>SyncProvider.UPDATABLE_VIEW_SYNC
 *     <LI>SyncProvider.NONUPDATABLE_VIEW_SYNC
 *   </UL>
 * </OL>
 *
 * @author Jonathan Bruce
 * @see javax.sql.rowset.spi.SyncFactory
 * @see javax.sql.rowset.spi.SyncFactoryException
 */
public abstract class SyncProvider {

   /**
    * Creates a default <code>SyncProvider</code> object.
    */
    public SyncProvider() {
    }       
    
    /**
     * Returns the unique identifier for this <code>SyncProvider</code> object. 
     * 
     * @return a <code>String</code> object with the fully qualified class name of
     *         this <code>SyncProvider</code> object