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- <title>javax.sql.rowset.spi</title>
-
-</head>
- <body>
-
-The standard classes and interfaces that a third party vendor has to
-use in its implementation of a synchronization provider. These classes and
-interfaces are referred to as the Service Provider Interface (SPI). To make it possible
-for a <code>RowSet</code> object to use an implementation, the vendor must register
-it with the <code>SyncFactory</code> singleton. (See the class comment for
-<code>SyncProvider</code> for a full explanation of the registration process and
-the naming convention to be used.)
-
-<h2>Table of Contents</h2>
-<ul>
-<li><a href="#pkgspec">1.0 Package Specification</a>
-<li><a href="#arch">2.0 Service Provider Architecture</a>
-<li><a href="#impl">3.0 Implementer's Guide</a>
-<li><a href="#resolving">4.0 Resolving Synchronization Conflicts</a>
-<li><a href="#relspec">5.0 Related Specifications</a>
-<li><a href="#reldocs">6.0 Related Documentation</a>
-</ul>
-
-<h3><a id="pkgspec">1.0 Package Specification</a></h3>
-<P>
-The following classes and interfaces make up the <code>javax.sql.rowset.spi</code>
-package:
-<UL>
- <LI><code>SyncFactory</code>
- <LI><code>SyncProvider</code>
- <LI><code>SyncFactoryException</code>
- <LI><code>SyncProviderException</code>
- <LI><code>SyncResolver</code>
- <LI><code>XmlReader</code>
- <LI><code>XmlWriter</code>
- <LI><code>TransactionalWriter</code>
-</UL>
-The following interfaces, in the <code>javax.sql</code> package, are also part of the SPI:
-<UL>
- <LI><code>RowSetReader</code>
- <LI><code>RowSetWriter</code>
-</UL>
-<P>
-A <code>SyncProvider</code> implementation provides a disconnected <code>RowSet</code>
-object with the mechanisms for reading data into it and for writing data that has been
-modified in it
-back to the underlying data source. A <i>reader</i>, a <code>RowSetReader</code> or
-<code>XMLReader</code> object, reads data into a <code>RowSet</code> object when the
-<code>CachedRowSet</code> methods <code>execute</code> or <code>populate</code>
-are called. A <i>writer</i>, a <code>RowSetWriter</code> or <code>XMLWriter</code>
-object, writes changes back to the underlying data source when the
-<code>CachedRowSet</code> method <code>acceptChanges</code> is called.
-<P>
-The process of writing changes in a <code>RowSet</code> object to its data source
-is known as <i>synchronization</i>. The <code>SyncProvider</code> implementation that a
-<code>RowSet</code> object is using determines the level of synchronization that the
-<code>RowSet</code> object's writer uses. The various levels of synchronization are
-referred to as <i>grades</i>.
-<P>
-The lower grades of synchronization are
-known as <i>optimistic</i> concurrency levels because they optimistically
-assume that there will be no conflicts or very few conflicts. A conflict exists when
-the same data modified in the <code>RowSet</code> object has also been modified
-in the data source. Using the optimistic concurrency model means that if there
-is a conflict, modifications to either the data source or the <code>RowSet</code>
-object will be lost.
-<P>
-Higher grades of synchronization are called <i>pessimistic</i> because they assume
-that others will be accessing the data source and making modifications. These
-grades set varying levels of locks to increase the chances that no conflicts
-occur.
-<P>
-The lowest level of synchronization is simply writing any changes made to the
-<code>RowSet</code> object to its underlying data source. The writer does
-nothing to check for conflicts.
-If there is a conflict and the data
-source values are overwritten, the changes other parties have made by to the data
-source are lost.
-<P>
-The <code>RIXMLProvider</code> implementation uses the lowest level
-of synchronization and just writes <code>RowSet</code> changes to the data source.
-
-<P>
-For the next level up, the
-writer checks to see if there are any conflicts, and if there are,
-it does not write anything to the data source. The problem with this concurrency
-level is that if another party has modified the corresponding data in the data source
-since the <code>RowSet</code> object got its data,
-the changes made to the <code>RowSet</code> object are lost. The
-<code>RIOptimisticProvider</code> implementation uses this level of synchronization.
-<P>
-At higher levels of synchronization, referred to as pessimistic concurrency,
-the writer take steps to avoid conflicts by setting locks. Setting locks
-can vary from setting a lock on a single row to setting a lock on a table
-or the entire data source. The level of synchronization is therefore a tradeoff
-between the ability of users to access the data source concurrently and the ability
-of the writer to keep the data in the <code>RowSet</code> object and its data source
-synchronized.
-<P>
-It is a requirement that all disconnected <code>RowSet</code> objects
-(<code>CachedRowSet</code>, <code>FilteredRowSet</code>, <code>JoinRowSet</code>,
-and <code>WebRowSet</code> objects) obtain their <code>SyncProvider</code> objects
-from the <code>SyncFactory</code> mechanism.
-<P>
-The reference implementation (RI) provides two synchronization providers.
- <UL>
- <LI><b><code>RIOptimisticProvider</code></b> <br>
- The default provider that the <code>SyncFactory</code> instance will
- supply to a disconnected <code>RowSet</code> object when no provider
- implementation is specified.<BR>
- This synchronization provider uses an optimistic concurrency model,
- assuming that there will be few conflicts among users
- who are accessing the same data in a database. It avoids
- using locks; rather, it checks to see if there is a conflict
- before trying to synchronize the <code>RowSet</code> object and the
- data source. If there is a conflict, it does nothing, meaning that
- changes to the <code>RowSet</code> object are not persisted to the data
- source.
- <LI><B><code>RIXMLProvider</code></B> <BR>
- A synchronization provider that can be used with a
- <code>WebRowSet</code> object, which is a rowset that can be written
- in XML format or read from XML format. The
- <code>RIXMLProvider</code> implementation does no checking at all for
- conflicts and simply writes any updated data in the
- <code>WebRowSet</code> object to the underlying data source.
- <code>WebRowSet</code> objects use this provider when they are
- dealing with XML data.
- </UL>
-
-These <code>SyncProvider</code> implementations
-are bundled with the reference implementation, which makes them always available to
-<code>RowSet</code> implementations.
-<code>SyncProvider</code> implementations make themselves available by being
-registered with the <code>SyncFactory</code> singleton. When a <code>RowSet</code>
-object requests a provider, by specifying it in the constructor or as an argument to the
-<code>CachedRowSet</code> method <code>setSyncProvider</code>,
-the <code>SyncFactory</code> singleton
-checks to see if the requested provider has been registered with it.
-If it has, the <code>SyncFactory</code> creates an instance of it and passes it to the
-requesting <code>RowSet</code> object.
-If the <code>SyncProvider</code> implementation that is specified has not been registered,
-the <code>SyncFactory</code> singleton causes a <code>SyncFactoryException</code> object
-to be thrown. If no provider is specified,
-the <code>SyncFactory</code> singleton will create an instance of the default
-provider implementation, <code>RIOptimisticProvider</code>,
-and pass it to the requesting <code>RowSet</code> object.
-
-<P>
-If a <code>WebRowSet</code> object does not specify a provider in its constructor, the
-<code>SyncFactory</code> will give it an instance of <code>RIOptimisticProvider</code>.
-However, the constructor for <code>WebRowSet</code> is implemented to set the provider
-to the <code>RIXMLProvider</code>, which reads and writes a <code>RowSet</code> object
-in XML format.
-<P>
-See the <a href="SyncProvider.html">SyncProvider</a> class
-specification for further details.
-<p>
-Vendors may develop a <code>SyncProvider</code> implementation with any one of the possible
-levels of synchronization, thus giving <code>RowSet</code> objects a choice of
-synchronization mechanisms.
-
-<h3><a id="arch">2.0 Service Provider Interface Architecture</a></h3>
-<b>2.1 Overview</b>
-<p>
-The Service Provider Interface provides a pluggable mechanism by which
-<code>SyncProvider</code> implementations can be registered and then generated when
-required. The lazy reference mechanism employed by the <code>SyncFactory</code> limits
-unnecessary resource consumption by not creating an instance until it is
-required by a disconnected
-<code>RowSet</code> object. The <code>SyncFactory</code> class also provides
-a standard API to configure logging options and streams that <b>may</b> be provided
-by a particular <code>SyncProvider</code> implementation.
-<p>
-<b>2.2 Registering with the <code>SyncFactory</code></b>
-<p>
-A third party <code>SyncProvider</code> implementation must be registered with the
-<code>SyncFactory</code> in order for a disconnected <code>RowSet</code> object
-to obtain it and thereby use its <code>javax.sql.RowSetReader</code> and
-<code>javax.sql.RowSetWriter</code>
-implementations. The following registration mechanisms are available to all
-<code>SyncProvider</code> implementations:
-<ul>
-<li><b>System properties</b> - Properties set at the command line. These
-properties are set at run time and apply system-wide per invocation of the Java
-application. See the section <a href="#reldocs">"Related Documentation"</a>
-further related information.
-
-<li><b>Property Files</b> - Properties specified in a standard property file.
-This can be specified using a System Property or by modifying a standard
-property file located in the platform run-time. The
-reference implementation of this technology includes a standard property
-file than can be edited to add additional <code>SyncProvider</code> objects.
-
-<li><b>JNDI Context</b> - Available providers can be registered on a JNDI
-context. The <code>SyncFactory</code> will attempt to load <code>SyncProvider</code>
-objects bound to the context and register them with the factory. This
-context must be supplied to the <code>SyncFactory</code> for the mechanism to
-function correctly.
-</ul>
-<p>
-Details on how to specify the system properties or properties in a property file
-and how to configure the JNDI Context are explained in detail in the
-<a href="SyncFactory.html"><code>SyncFactory</code></a> class description.
-<p>
-<b>2.3 SyncFactory Provider Instance Generation Policies</b>
-<p>
-The <code>SyncFactory</code> generates a requested <code>SyncProvider</code>
-object if the provider has been correctly registered. The
-following policies are adhered to when either a disconnected <code>RowSet</code> object
-is instantiated with a specified <code>SyncProvider</code> implementation or is
-reconfigured at runtime with an alternative <code>SyncProvider</code> object.
-<ul>
-<li> If a <code>SyncProvider</code> object is specified and the <code>SyncFactory</code>
-contains <i>no</i> reference to the provider, a <code>SyncFactoryException</code> is
-thrown.
-
-<li> If a <code>SyncProvider</code> object is specified and the <code>SyncFactory</code>
-contains a reference to the provider, the requested provider is supplied.
-
-<li> If no <code>SyncProvider</code> object is specified, the reference
-implementation provider <code>RIOptimisticProvider</code> is supplied.
-</ul>
-<p>
-These policies are explored in more detail in the <a href="SyncFactory.html">
-<code>SyncFactory</code></a> class.
-
-<h3><a id="impl">3.0 SyncProvider Implementer's Guide</a></h3>
-
-<b>3.1 Requirements</b>
-<p>
-A compliant <code>SyncProvider</code> implementation that is fully pluggable
-into the <code>SyncFactory</code> <b>must</b> extend and implement all
-abstract methods in the <a href="SyncProvider.html"><code>SyncProvider</code></a>
-class. In addition, an implementation <b>must</b> determine the
-grade, locking and updatable view capabilities defined in the
-<code>SyncProvider</code> class definition. One or more of the
-<code>SyncProvider</code> description criteria <b>must</b> be supported. It
-is expected that vendor implementations will offer a range of grade, locking, and
-updatable view capabilities.
-<p>
-Furthermore, the <code>SyncProvider</code> naming convention <b>must</b> be followed as
-detailed in the <a href="SyncProvider.html"><code>SyncProvider</code></a> class
-description.
-<p>
-<b>3.2 Grades</b>
-<p>
-JSR 114 defines a set of grades to describe the quality of synchronization
-a <code>SyncProvider</code> object can offer a disconnected <code>RowSet</code>
-object. These grades are listed from the lowest quality of service to the highest.
-<ul>
-<li><b>GRADE_NONE</b> - No synchronization with the originating data source is
-provided. A <code>SyncProvider</code> implementation returning this grade will simply
-attempt to write any data that has changed in the <code>RowSet</code> object to the
-underlying data source, overwriting whatever is there. No attempt is made to compare
-original values with current values to see if there is a conflict. The
-<code>RIXMLProvider</code> is implemented with this grade.
-
-<li><b>GRADE_CHECK_MODIFIED_AT_COMMIT</b> - A low grade of optimistic synchronization.
-A <code>SyncProvider</code> implementation returning this grade
-will check for conflicts in rows that have changed between the last synchronization
-and the current synchronization under way. Any changes in the originating data source
-that have been modified will not be reflected in the disconnected <code>RowSet</code>
-object. If there are no conflicts, changes in the <code>RowSet</code> object will be
-written to the data source. If there are conflicts, no changes are written.
-The <code>RIOptimisticProvider</code> implementation uses this grade.
-
-<li><b>GRADE_CHECK_ALL_AT_COMMIT</b> - A high grade of optimistic synchronization.
-A <code>SyncProvider</code> implementation returning this grade
-will check all rows, including rows that have not changed in the disconnected
-<code>RowSet</code> object. In this way, any changes to rows in the underlying
-data source will be reflected in the disconnected <code>RowSet</code> object
-when the synchronization finishes successfully.
-
-<li><b>GRADE_LOCK_WHEN_MODIFIED</b> - A pessimistic grade of synchronization.
-<code>SyncProvider</code> implementations returning this grade will lock
-the row in the originating data source that corresponds to the row being changed
-in the <code>RowSet</code> object to reduce the possibility of other
-processes modifying the same data in the data source.
-
-<li><b>GRADE_LOCK_WHEN_LOADED</b> - A higher pessimistic synchronization grade.
-A <code>SyncProvider</code> implementation returning this grade will lock
-the entire view and/or table affected by the original query used to
-populate a <code>RowSet</code> object.
-</ul>
-<p>
-<b>3.3 Locks</b>
-<p>
-JSR 114 defines a set of constants that specify whether any locks have been
-placed on a <code>RowSet</code> object's underlying data source and, if so,
-on which constructs the locks are placed. These locks will remain on the data
-source while the <code>RowSet</code> object is disconnected from the data source.
-<P>
-These constants <b>should</b> be considered complementary to the
-grade constants. The default setting for the majority of grade settings requires
-that no data source locks remain when a <code>RowSet</code> object is disconnected
-from its data source.
-The grades <code>GRADE_LOCK_WHEN_MODIFIED</code> and
-<code>GRADE_LOCK_WHEN_LOADED</code> allow a disconnected <code>RowSet</code> object
-to have a fine-grained control over the degree of locking.
-<ul>
-<li><b>DATASOURCE_NO_LOCK</b> - 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.
-
-<li><b>DATASOURCE_ROW_LOCK</b> - A lock is placed on the rows that are touched by
-the original SQL query used to populate the <code>RowSet</code> object.
-
-<li><b>DATASOURCE_TABLE_LOCK</b> - A lock is placed on all tables that are touched
-by the query that was used to populate the <code>RowSet</code> object.
-
-<li><b>DATASOURCE_DB_LOCK</b>
-A lock is placed on the entire data source that is used by the <code>RowSet</code>
-object.
-</ul>
-<p>
-<b>3.4 Updatable Views</b>
-<p>
-A <code>RowSet</code> object may be populated with data from an SQL <code>VIEW</code>.
-The following constants indicate whether a <code>SyncProvider</code> object can
-update data in the table or tables from which the <code>VIEW</code> was derived.
-<ul>
-<li><b>UPDATABLE_VIEW_SYNC</b>
-Indicates that a <code>SyncProvider</code> implementation supports synchronization
-to the table or tables from which the SQL <code>VIEW</code> used to populate
-a <code>RowSet</code> object is derived.
-
-<li><b>NONUPDATABLE_VIEW_SYNC</b>
-Indicates that a <code>SyncProvider</code> implementation does <b>not</b> support
-synchronization to the table or tables from which the SQL <code>VIEW</code>
-used to populate a <code>RowSet</code> object is derived.
-</ul>
-<p>
-<b>3.5 Usage of <code>SyncProvider</code> Grading and Locking</b>
-<p>
-In the example below, the reference <code>CachedRowSetImpl</code> implementation
-reconfigures its current <code>SyncProvider</code> object by calling the
-<code>setSyncProvider</code> method.<br>
-
-<PRE>
- CachedRowSetImpl crs = new CachedRowSetImpl();
- crs.setSyncProvider("com.foo.bar.HASyncProvider");
-</PRE>
- An application can retrieve the <code>SyncProvider</code> object currently in use
-by a disconnected <code>RowSet</code> object. It can also retrieve the
-grade of synchronization with which the provider was implemented and the degree of
-locking currently in use. In addition, an application has the flexibility to set
-the degree of locking to be used, which can increase the possibilities for successful
-synchronization. These operation are shown in the following code fragment.
-<PRE>
- SyncProvider sync = crs.getSyncProvider();
-
- switch (sync.getProviderGrade()) {
- case: SyncProvider.GRADE_CHECK_ALL_AT_COMMIT
- //A high grade of optimistic synchronization
- break;
- case: SyncProvider.GRADE_CHECK_MODIFIED_AT_COMMIT
- //A low grade of optimistic synchronization
- break;
- case: SyncProvider.GRADE_LOCK_WHEN_LOADED
- // A pessimistic synchronization grade
- break;
- case: SyncProvider.GRADE_LOCK_WHEN_MODIFIED
- // A pessimistic synchronization grade
- break;
- case: SyncProvider.GRADE_NONE
- // No synchronization with the originating data source provided
- break;
- }
-
- switch (sync.getDataSourcLock() {
- case: SyncProvider.DATASOURCE_DB_LOCK
- // A lock is placed on the entire datasource that is used by the
- // <code>RowSet</code> object
- break;
-
- case: SyncProvider.DATASOURCE_NO_LOCK
- // No locks remain on the originating data source.
- break;
-
- case: SyncProvider.DATASOURCE_ROW_LOCK
- // A lock is placed on the rows that are touched by the original
- // SQL statement used to populate
- // the RowSet object that is using the SyncProvider
- break;
-
- case: DATASOURCE_TABLE_LOCK
- // A lock is placed on all tables that are touched by the original
- // SQL statement used to populated
- // the RowSet object that is using the SyncProvider
- break;
-
-</PRE>
- It is also possible using the static utility method in the
-<code>SyncFactory</code> class to determine the list of <code>SyncProvider</code>
-implementations currently registered with the <code>SyncFactory</code>.
-
-<pre>
- Enumeration e = SyncFactory.getRegisteredProviders();
-</pre>
-
-
-<h3><a id="resolving">4.0 Resolving Synchronization Conflicts</a></h3>
-
-The interface <code>SyncResolver</code> provides a way for an application to
-decide manually what to do when a conflict occurs. When the <code>CachedRowSet</code>
-method <code>acceptChanges</code> finishes and has detected one or more conflicts,
-it throws a <code>SyncProviderException</code> object. An application can
-catch the exception and
-have it retrieve a <code>SyncResolver</code> object by calling the method
-<code>SyncProviderException.getSyncResolver()</code>.
-<P>
-A <code>SyncResolver</code> object, which is a special kind of
-<code>CachedRowSet</code> object or
-a <code>JdbcRowSet</code> object that has implemented the <code>SyncResolver</code>
-interface, examines the conflicts row by row. It is a duplicate of the
-<code>RowSet</code> object being synchronized except that it contains only the data
-from the data source this is causing a conflict. All of the other column values are
-set to <code>null</code>. To navigate from one conflict value to another, a
-<code>SyncResolver</code> object provides the methods <code>nextConflict</code> and
-<code>previousConflict</code>.
-<P>
-The <code>SyncResolver</code> interface also
-provides methods for doing the following:
-<UL>
- <LI>finding out whether the conflict involved an update, a delete, or an insert
- <LI>getting the value in the data source that caused the conflict
- <LI>setting the value that should be in the data source if it needs to be changed
- or setting the value that should be in the <code>RowSet</code> object if it needs
- to be changed
-</UL>
-<P>
-When the <code>CachedRowSet</code> method <code>acceptChanges</code> is called, it
-delegates to the <code>RowSet</code> object's <code>SyncProvider</code> object.
-How the writer provided by that <code>SyncProvider</code> object is implemented
-determines what level (grade) of checking for conflicts will be done. After all
-checking for conflicts is completed and one or more conflicts has been found, the method
-<code>acceptChanges</code> throws a <code>SyncProviderException</code> object. The
-application can catch the exception and use it to obtain a <code>SyncResolver</code> object.
-<P>
-The application can then use <code>SyncResolver</code> methods to get information
-about each conflict and decide what to do. If the application logic or the user
-decides that a value in the <code>RowSet</code> object should be the one to
-persist, the application or user can overwrite the data source value with it.
-<P>
-The comment for the <code>SyncResolver</code> interface has more detail.
-
-<h3><a id="relspec">5.0 Related Specifications</a></h3>
-<ul>
-<li><a href="http://docs.oracle.com/javase/jndi/tutorial/index.html">JNDI</a>
-<li><a href="{@docRoot}/java/util/logging/package-summary.html">Java Logging
-APIs</a>
-</ul>
-<h3><a id="reldocs">6.0 Related Documentation</a></h3>
-<ul>
-<li><a href="http://docs.oracle.com/javase/tutorial/jdbc/">DataSource for JDBC
-Connections</a>
-</ul>
-
-</body>
-</html>