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package javax.naming.spi;
import javax.naming.*;
import java.util.Hashtable;
/**
* This interface represents a factory for obtaining the state of an
* object for binding.
*<p>
* The JNDI framework allows for object implementations to
* be loaded in dynamically via <em>object factories</em>.
* For example, when looking up a printer bound in the name space,
* if the print service binds printer names to {@code Reference}s, the printer
* {@code Reference} could be used to create a printer object, so that
* the caller of lookup can directly operate on the printer object
* after the lookup.
* <p>An {@code ObjectFactory} is responsible
* for creating objects of a specific type. In the above example,
* you may have a {@code PrinterObjectFactory} for creating
* {@code Printer} objects.
* <p>
* For the reverse process, when an object is bound into the namespace,
* JNDI provides <em>state factories</em>.
* Continuing with the printer example, suppose the printer object is
* updated and rebound:
* <blockquote><pre>
* ctx.rebind("inky", printer);
* </pre></blockquote>
* The service provider for {@code ctx} uses a state factory
* to obtain the state of {@code printer} for binding into its namespace.
* A state factory for the {@code Printer} type object might return
* a more compact object for storage in the naming system.
*<p>
* A state factory must implement the {@code StateFactory} interface.
* In addition, the factory class must be public and must have a
* public constructor that accepts no parameters.
* Note that in cases where the factory is in a named module then it must be
* in a package which is exported by that module to the {@code java.naming}
* module.
*<p>
* The {@code getStateToBind()} method of a state factory may
* be invoked multiple times, possibly using different parameters.
* The implementation is thread-safe.
*<p>
* {@code StateFactory} is intended for use with service providers
* that implement only the {@code Context} interface.
* {@code DirStateFactory} is intended for use with service providers
* that implement the {@code DirContext} interface.
*
* @author Rosanna Lee
* @author Scott Seligman
*
* @see NamingManager#getStateToBind
* @see DirectoryManager#getStateToBind
* @see ObjectFactory
* @see DirStateFactory
* @since 1.3
*/
public interface StateFactory {
/**
* Retrieves the state of an object for binding.
*<p>
* {@code NamingManager.getStateToBind()}
* successively loads in state factories and invokes this method
* on them until one produces a non-null answer.
* {@code DirectoryManager.getStateToBind()}
* successively loads in state factories. If a factory implements
* {@code DirStateFactory}, then {@code DirectoryManager}
* invokes {@code DirStateFactory.getStateToBind()}; otherwise
* it invokes {@code StateFactory.getStateToBind()}.
*<p> When an exception
* is thrown by a factory, the exception is passed on to the caller
* of {@code NamingManager.getStateToBind()} and
* {@code DirectoryManager.getStateToBind()}.
* The search for other factories
* that may produce a non-null answer is halted.
* A factory should only throw an exception if it is sure that
* it is the only intended factory and that no other factories
* should be tried.
* If this factory cannot create an object using the arguments supplied,
* it should return null.
* <p>
* The <code>name</code> and <code>nameCtx</code> parameters may
* optionally be used to specify the name of the object being created.
* See the description of "Name and Context Parameters" in
* {@link ObjectFactory#getObjectInstance ObjectFactory.getObjectInstance()}
* for details.
* If a factory uses <code>nameCtx</code> it should synchronize its use
* against concurrent access, since context implementations are not
* guaranteed to be thread-safe.
* <p>
* The {@code name} and {@code environment} parameters
* are owned by the caller.
* The implementation will not modify these objects or keep references
* to them, although it may keep references to clones or copies.
*
* @param obj A non-null object whose state is to be retrieved.
* @param name The name of this object relative to <code>nameCtx</code>,
* or null if no name is specified.
* @param nameCtx The context relative to which the <code>name</code>
* parameter is specified, or null if <code>name</code> is
* relative to the default initial context.
* @param environment The possibly null environment to
* be used in the creation of the object's state.
* @return The object's state for binding;
* null if the factory is not returning any changes.
* @exception NamingException if this factory encountered an exception
* while attempting to get the object's state, and no other factories are
* to be tried.
*
* @see NamingManager#getStateToBind
* @see DirectoryManager#getStateToBind
*/
public Object getStateToBind(Object obj, Name name, Context nameCtx,
Hashtable<?,?> environment)
throws NamingException;
}