StateFactory.java

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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.
 * @throws 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;
}