/*
 * @(#)StateFactory.java	1.6 01/12/03
 *
 * Copyright 2002 Sun Microsystems, Inc. All rights reserved.
 * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */
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 <tt>Reference</tt>s, the printer
  * <tt>Reference</tt> 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 <tt>ObjectFactory</tt> is responsible
  * for creating objects of a specific type.  In the above example,
  * you may have a <tt>PrinterObjectFactory</tt> for creating 
  * <tt>Printer</tt> 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 <tt>ctx</tt> uses a state factory
  * to obtain the state of <tt>printer</tt> for binding into its namespace.
  * A state factory for the <tt>Printer</tt> type object might return
  * a more compact object for storage in the naming system.
  *<p>
  * A state factory must implement the <tt>StateFactory</tt> interface.
  * In addition, the factory class must be public and must have a 
  * public constructor that accepts no parameters.
  *<p>
  * The <tt>getStateToBind()</tt> method of a state factory may
  * be invoked multiple times, possibly using different parameters.
  * The implementation is thread-safe.
  *<p>
  * <tt>StateFactory</tt> is intended for use with service providers
  * that implement only the <tt>Context</tt> interface.
  * <tt>DirStateFactory</tt> is intended for use with service providers
  * that implement the <tt>DirContext</tt> interface.
  *
  * @author Rosanna Lee
  * @author Scott Seligman
  * @version 1.6 01/12/03
  *
  * @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>
 * <tt>NamingManager.getStateToBind()</tt>
 * successively loads in state factories and invokes this method
 * on them until one produces a non-null answer.  
 * <tt>DirectoryManager.getStateToBind()</tt>
 * successively loads in state factories.  If a factory implements
 * <tt>DirStateFactory</tt>, then <tt>DirectoryManager</tt>
 * invokes <tt>DirStateFactory.getStateToBind()</tt>; otherwise
 * it invokes <tt>StateFactory.getStateToBind()</tt>.
 *<p> When an exception
 * is thrown by a factory, the exception is passed on to the caller
 * of <tt>NamingManager.getStateToBind()</tt> and
 * <tt>DirectoryManager.getStateToBind()</tt>. 
 * 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 <tt>name</tt> and <tt>environment</tt> 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;
}
