# Class SyncFactory

java.lang.Object
javax.sql.rowset.spi.SyncFactory

public class SyncFactory extends Object
The Service Provider Interface (SPI) mechanism that generates `SyncProvider` instances to be used by disconnected `RowSet` objects. The `SyncProvider` instances in turn provide the `javax.sql.RowSetReader` object the `RowSet` object needs to populate itself with data and the `javax.sql.RowSetWriter` object it needs to propagate changes to its data back to the underlying data source.

Because the methods in the `SyncFactory` class are all static, there is only one `SyncFactory` object per Java VM at any one time. This ensures that there is a single source from which a `RowSet` implementation can obtain its `SyncProvider` implementation.

## 1.0 Overview

The `SyncFactory` class provides an internal registry of available synchronization provider implementations (`SyncProvider` objects). This registry may be queried to determine which synchronization providers are available. The following line of code gets an enumeration of the providers currently registered.

        java.util.Enumeration e = SyncFactory.getRegisteredProviders();

All standard `RowSet` implementations must provide at least two providers:

- an optimistic provider for use with a `CachedRowSet` implementation or an implementation derived from it
- an XML provider, which is used for reading and writing XML, such as with `WebRowSet` objects

Note that the JDBC RowSet Implementations include the `SyncProvider` implementations `RIOptimisticProvider` and `RIXmlProvider`, which satisfy this requirement.

The `SyncFactory` class provides accessor methods to assist applications in determining which synchronization providers are currently registered with the `SyncFactory`.

Other methods let `RowSet` persistence providers be registered or de-registered with the factory mechanism. This allows additional synchronization provider implementations to be made available to `RowSet` objects at run time.

Applications can apply a degree of filtering to determine the level of synchronization that a `SyncProvider` implementation offers. The following criteria determine whether a provider is made available to a `RowSet` object:

1. If a particular provider is specified by a `RowSet` object, and the `SyncFactory` does not contain a reference to this provider, a `SyncFactoryException` is thrown stating that the synchronization provider could not be found.
2. If a `RowSet` implementation is instantiated with a specified provider and the specified provider has been properly registered, the requested provider is supplied. Otherwise a `SyncFactoryException` is thrown.
3. If a `RowSet` object does not specify a `SyncProvider` implementation and no additional `SyncProvider` implementations are available, the reference implementation providers are supplied.

## 2.0 Registering `SyncProvider` Implementations

Both vendors and developers can register `SyncProvider` implementations using one of the following mechanisms.

- Using the command line
  The name of the provider is supplied on the command line, which will add the provider to the system properties. For example:

         -Drowset.provider.classname=com.fred.providers.HighAvailabilityProvider

- Using the Standard Properties File
  The reference implementation is targeted to ship with J2SE 1.5, which will include an additional resource file that may be edited by hand. Here is an example of the properties file included in the reference implementation:

        #Default JDBC RowSet sync providers listing
        #

        # Optimistic synchronization provider
        rowset.provider.classname.0=com.sun.rowset.providers.RIOptimisticProvider
        rowset.provider.vendor.0=Oracle Corporation
        rowset.provider.version.0=1.0

        # XML Provider using standard XML schema
        rowset.provider.classname.1=com.sun.rowset.providers.RIXMLProvider
        rowset.provider.vendor.1=Oracle Corporation
        rowset.provider.version.1=1.0

  The `SyncFactory` checks this file and registers the `SyncProvider` implementations that it contains. A developer or vendor can add other implementations to this file. For example, here is a possible addition:

          rowset.provider.classname.2=com.fred.providers.HighAvailabilityProvider
          rowset.provider.vendor.2=Fred, Inc.
          rowset.provider.version.2=1.0

- Using a JNDI Context
  Available providers can be registered on a JNDI context, and the `SyncFactory` will attempt to load `SyncProvider` implementations from that JNDI context. For example, the following code fragment registers a provider implementation on a JNDI context. This is something a deployer would normally do. In this example, `MyProvider` is being registered on a CosNaming namespace, which is the namespace used by J2EE resources.

         import javax.naming.*;

         Hashtable svrEnv = new  Hashtable();
         srvEnv.put(Context.INITIAL_CONTEXT_FACTORY, "CosNaming");

         Context ctx = new InitialContext(svrEnv);
         com.fred.providers.MyProvider = new MyProvider();
         ctx.rebind("providers/MyProvider", syncProvider);

Next, an application will register the JNDI context with the `SyncFactory` instance. This allows the `SyncFactory` to browse within the JNDI context looking for `SyncProvider` implementations.

       Hashtable appEnv = new Hashtable();
       appEnv.put(Context.INITIAL_CONTEXT_FACTORY, "CosNaming");
       appEnv.put(Context.PROVIDER_URL, "iiop://hostname/providers");
       Context ctx = new InitialContext(appEnv);

       SyncFactory.registerJNDIContext(ctx);

If a `RowSet` object attempts to obtain a `MyProvider` object, the `SyncFactory` will try to locate it. First it searches for it in the system properties, then it looks in the resource files, and finally it checks the JNDI context that has been set. The `SyncFactory` instance verifies that the requested provider is a valid extension of the `SyncProvider` abstract class and then gives it to the `RowSet` object. In the following code fragment, a new `CachedRowSet` object is created and initialized with env, which contains the binding to `MyProvider`.

       Hashtable env = new Hashtable();
       env.put(SyncFactory.ROWSET_SYNC_PROVIDER, "com.fred.providers.MyProvider");
       CachedRowSet crs = new com.sun.rowset.CachedRowSetImpl(env);

Further details on these mechanisms are available in the `javax.sql.rowset.spi` package specification.

Since:
  1.5
See Also:
  - `SyncProvider`
  - `SyncFactoryException`

- ## Field Summary

  Fields
  Modifier and Type
  Field
  Description
  `static final String`
  `ROWSET_SYNC_PROVIDER`
  The standard property-id for a synchronization provider implementation name.
  `static final String`
  `ROWSET_SYNC_PROVIDER_VERSION`
  The standard property-id for a synchronization provider implementation version tag.
  `static final String`
  `ROWSET_SYNC_VENDOR`
  The standard property-id for a synchronization provider implementation vendor name.

- ## Method Summary

  Modifier and Type
  Method
  Description
  `static SyncProvider`
  `getInstance(String providerID)`
  Returns the `SyncProvider` instance identified by providerID.
  `static Logger`
  `getLogger()`
  Returns the logging object for applications to retrieve synchronization events posted by SyncProvider implementations.
  `static Enumeration<SyncProvider>`
  `getRegisteredProviders()`
  Returns an Enumeration of currently registered synchronization providers.
  `static SyncFactory`
  `getSyncFactory()`
  Returns the `SyncFactory` singleton.
  `static void`
  `registerProvider(String providerID)`
  Adds the given synchronization provider to the factory register.
  `static void`
  `setJNDIContext(Context ctx)`
  Sets the initial JNDI context from which SyncProvider implementations can be retrieved from a JNDI namespace
  `static void`
  `setLogger(Logger logger)`
  Sets the logging object to be used by the `SyncProvider` implementation provided by the `SyncFactory`.
  `static void`
  `setLogger(Logger logger, Level level)`
  Sets the logging object that is used by `SyncProvider` implementations provided by the `SyncFactory` SPI.
  `static void`
  `unregisterProvider(String providerID)`
  Removes the designated currently registered synchronization provider from the Factory SPI register.

  ### Methods declared in class Object

  `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

- ## Field Details

  - ### ROWSET_SYNC_PROVIDER

    public static final String ROWSET_SYNC_PROVIDER
    The standard property-id for a synchronization provider implementation name.
    See Also:
      - Constant Field Values

  - ### ROWSET_SYNC_VENDOR

    public static final String ROWSET_SYNC_VENDOR
    The standard property-id for a synchronization provider implementation vendor name.
    See Also:
      - Constant Field Values

  - ### ROWSET_SYNC_PROVIDER_VERSION

    public static final String ROWSET_SYNC_PROVIDER_VERSION
    The standard property-id for a synchronization provider implementation version tag.
    See Also:
      - Constant Field Values

- ## Method Details

  - ### registerProvider

    public static void registerProvider(String providerID) throws SyncFactoryException
    Adds the given synchronization provider to the factory register. Guidelines are provided in the `SyncProvider` specification for the required naming conventions for `SyncProvider` implementations.

    Synchronization providers bound to a JNDI context can be registered by binding a SyncProvider instance to a JNDI namespace.

        SyncProvider p = new MySyncProvider();
        InitialContext ic = new InitialContext();
        ic.bind ("jdbc/rowset/MySyncProvider", p);

    Furthermore, an initial JNDI context should be set with the `SyncFactory` using the `setJNDIContext` method. The `SyncFactory` leverages this context to search for available `SyncProvider` objects bound to the JNDI context and its child nodes.
    Parameters:
      `providerID` - A `String` object with the unique ID of the synchronization provider being registered
    Throws:
      `SyncFactoryException` - if an attempt is made to supply an empty or null provider name
    See Also:
      - `setJNDIContext(Context)`

  - ### getSyncFactory

    public static SyncFactory getSyncFactory()
    Returns the `SyncFactory` singleton.
    Returns:
      the `SyncFactory` instance

  - ### unregisterProvider

    public static void unregisterProvider(String providerID) throws SyncFactoryException
    Removes the designated currently registered synchronization provider from the Factory SPI register.
    Parameters:
      `providerID` - The unique-id of the synchronization provider
    Throws:
      `SyncFactoryException` - If an attempt is made to unregister a SyncProvider implementation that was not registered.

  - ### getInstance

    public static SyncProvider getInstance(String providerID) throws SyncFactoryException
    Returns the `SyncProvider` instance identified by providerID.
    Parameters:
      `providerID` - the unique identifier of the provider
    Returns:
      a `SyncProvider` implementation
    Throws:
      `SyncFactoryException` - If the SyncProvider cannot be found, the providerID is `null`, or some error was encountered when trying to invoke this provider.

  - ### getRegisteredProviders

    public static Enumeration<SyncProvider> getRegisteredProviders() throws SyncFactoryException
    Returns an Enumeration of currently registered synchronization providers. A `RowSet` implementation may use any provider in the enumeration as its `SyncProvider` object.

    At a minimum, the reference synchronization provider allowing RowSet content data to be stored using a JDBC driver should be possible.

    Returns:
      Enumeration A enumeration of available synchronization providers that are registered with this Factory
    Throws:
      `SyncFactoryException` - If an error occurs obtaining the registered providers

  - ### setLogger

    public static void setLogger(Logger logger)
    Sets the logging object to be used by the `SyncProvider` implementation provided by the `SyncFactory`. All `SyncProvider` implementations can log their events to this object and the application can retrieve a handle to this object using the `getLogger` method.
    Parameters:
      `logger` - A Logger object instance
    Throws:
      `NullPointerException` - if the logger is null

  - ### setLogger

    public static void setLogger(Logger logger, Level level)
    Sets the logging object that is used by `SyncProvider` implementations provided by the `SyncFactory` SPI. All `SyncProvider` implementations can log their events to this object and the application can retrieve a handle to this object using the `getLogger` method.
    Parameters:
      `logger` - a Logger object instance
      `level` - a Level object instance indicating the degree of logging required
    Throws:
      `NullPointerException` - if the logger is null

  - ### getLogger

    public static Logger getLogger() throws SyncFactoryException
    Returns the logging object for applications to retrieve synchronization events posted by SyncProvider implementations.
    Returns:
      The `Logger` that has been specified for use by `SyncProvider` implementations
    Throws:
      `SyncFactoryException` - if no logging object has been set.

  - ### setJNDIContext

    public static void setJNDIContext(Context ctx) throws SyncFactoryException
    Sets the initial JNDI context from which SyncProvider implementations can be retrieved from a JNDI namespace
    Parameters:
      `ctx` - a valid JNDI context
    Throws:
      `SyncFactoryException` - if the supplied JNDI context is null