Java tutorial
/* * Copyright (c) 2003, 2019, 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.*; /** * 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. * * <h2>1.0 Naming Convention for Implementations</h2> * 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 Oracle Corporation by sending email to jdbc@sun.com. * Oracle 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. * * <h2>2.0 How a <code>RowSet</code> Object Gets Its Provider</h2> * * 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>. * * <h2>3.0 Violations and Synchronization Issues</h2> * 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>. * * <h2>4.0 Updatable SQL VIEWs</h2> * 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>. * * <h2>5.0 <code>SyncProvider</code> Constants</h2> * 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 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 * @since 1.5 */ 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 */ public abstract String getProviderID(); /** * Returns a <code>javax.sql.RowSetReader</code> object, which can be used to * populate a <code>RowSet</code> object with data. * * @return a <code>javax.sql.RowSetReader</code> object */ public abstract RowSetReader getRowSetReader(); /** * Returns a <code>javax.sql.RowSetWriter</code> object, which can be * used to write a <code>RowSet</code> object's data back to the * underlying data source. * * @return a <code>javax.sql.RowSetWriter</code> object */ public abstract RowSetWriter getRowSetWriter(); /** * Returns a constant indicating the * grade of synchronization a <code>RowSet</code> object can expect from * this <code>SyncProvider</code> object. * * @return an int that is one of the following constants: * SyncProvider.GRADE_NONE, * SyncProvider.GRADE_CHECK_MODIFIED_AT_COMMIT, * SyncProvider.GRADE_CHECK_ALL_AT_COMMIT, * SyncProvider.GRADE_LOCK_WHEN_MODIFIED, * SyncProvider.GRADE_LOCK_WHEN_LOADED */ public abstract int getProviderGrade(); /** * Sets a lock on the underlying data source at the level indicated by * <i>datasource_lock</i>. This should cause the * <code>SyncProvider</code> to adjust its behavior by increasing or * decreasing the level of optimism it provides for a successful * synchronization. * * @param datasource_lock one of the following constants indicating the severity * level of data source lock required: * <pre> * SyncProvider.DATASOURCE_NO_LOCK, * SyncProvider.DATASOURCE_ROW_LOCK, * SyncProvider.DATASOURCE_TABLE_LOCK, * SyncProvider.DATASOURCE_DB_LOCK, * </pre> * @throws SyncProviderException if an unsupported data source locking level * is set. * @see #getDataSourceLock */ public abstract void setDataSourceLock(int datasource_lock) throws SyncProviderException; /** * Returns the current data source lock severity level active in this * <code>SyncProvider</code> implementation. * * @return a constant indicating the current level of data source lock * active in this <code>SyncProvider</code> object; * one of the following: * <pre> * SyncProvider.DATASOURCE_NO_LOCK, * SyncProvider.DATASOURCE_ROW_LOCK, * SyncProvider.DATASOURCE_TABLE_LOCK, * SyncProvider.DATASOURCE_DB_LOCK * </pre> * @throws SyncProviderException if an error occurs determining the data * source locking level. * @see #setDataSourceLock */ public abstract int getDataSourceLock() throws SyncProviderException; /** * Returns whether this <code>SyncProvider</code> implementation * can perform synchronization between a <code>RowSet</code> object * and the SQL <code>VIEW</code> in the data source from which * the <code>RowSet</code> object got its data. * * @return an <code>int</code> saying whether this <code>SyncProvider</code> * object supports updating an SQL <code>VIEW</code>; one of the * following: * SyncProvider.UPDATABLE_VIEW_SYNC, * SyncProvider.NONUPDATABLE_VIEW_SYNC */ public abstract int supportsUpdatableView(); /** * Returns the release version of this <code>SyncProvider</code> instance. * * @return a <code>String</code> detailing the release version of the * <code>SyncProvider</code> implementation */ public abstract String getVersion(); /** * Returns the vendor name of this <code>SyncProvider</code> instance * * @return a <code>String</code> detailing the vendor name of this * <code>SyncProvider</code> implementation */ public abstract String getVendor(); /* * Standard description of synchronization grades that a SyncProvider * could provide. */ /** * Indicates that no synchronization with the originating data source is * provided. A <code>SyncProvider</code> * implementation returning this grade will simply attempt to write * updates in the <code>RowSet</code> object to the underlying data * source without checking the validity of any data. * */ public static final int GRADE_NONE = 1; /** * Indicates a low level optimistic synchronization grade with * respect to the originating data source. * * A <code>SyncProvider</code> implementation * returning this grade will check only rows that have changed. * */ public static final int GRADE_CHECK_MODIFIED_AT_COMMIT = 2; /** * Indicates a high level optimistic synchronization grade with * respect to the originating data source. * * A <code>SyncProvider</code> implementation * returning this grade will check all rows, including rows that have not * changed. */ public static final int GRADE_CHECK_ALL_AT_COMMIT = 3; /** * Indicates a pessimistic synchronization grade with * respect to the originating data source. * * A <code>SyncProvider</code> * implementation returning this grade will lock the row in the originating * data source. */ public static final int GRADE_LOCK_WHEN_MODIFIED = 4; /** * Indicates the most pessimistic synchronization grade with * respect to the originating * data source. A <code>SyncProvider</code> * implementation returning this grade will lock the entire view and/or * table affected by the original statement used to populate a * <code>RowSet</code> object. */ public static final int GRADE_LOCK_WHEN_LOADED = 5; /** * Indicates that no locks remain on the originating data source. This is the default * lock setting for all <code>SyncProvider</code> implementations unless * otherwise directed by a <code>RowSet</code> object. */ public static final int DATASOURCE_NO_LOCK = 1; /** * Indicates that a lock is placed on the rows that are touched by the original * SQL statement used to populate the <code>RowSet</code> object * that is using this <code>SyncProvider</code> object. */ public static final int DATASOURCE_ROW_LOCK = 2; /** * Indicates that a lock is placed on all tables that are touched by the original * SQL statement used to populate the <code>RowSet</code> object * that is using this <code>SyncProvider</code> object. */ public static final int DATASOURCE_TABLE_LOCK = 3; /** * Indicates that a lock is placed on the entire data source that is the source of * data for the <code>RowSet</code> object * that is using this <code>SyncProvider</code> object. */ public static final int DATASOURCE_DB_LOCK = 4; /** * Indicates that a <code>SyncProvider</code> implementation * supports synchronization between a <code>RowSet</code> object and * the SQL <code>VIEW</code> used to populate it. */ public static final int UPDATABLE_VIEW_SYNC = 5; /** * Indicates that a <code>SyncProvider</code> implementation * does <B>not</B> support synchronization between a <code>RowSet</code> * object and the SQL <code>VIEW</code> used to populate it. */ public static final int NONUPDATABLE_VIEW_SYNC = 6; }