/*
 * @(#)BeanContextServiceProvider.java	1.10 03/12/19
 *
 * Copyright 2004 Sun Microsystems, Inc. All rights reserved.
 * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */

package java.beans.beancontext;

import java.util.Iterator;

/**
 * <p>
 * One of the primary functions of a BeanContext is to act a as rendezvous 
 * between JavaBeans, and BeanContextServiceProviders.
 * </p>
 * <p>
 * A JavaBean nested within a BeanContext, may ask that BeanContext to 
 * provide an instance of a "service", based upon a reference to a Java
 * Class object that represents that service.
 * </p>
 * <p>
 * If such a service has been registered with the context, or one of its 
 * nesting context's, in the case where a context delegate to its context
 * to satisfy a service request, then the BeanContextServiceProvider associated with 
 * the service is asked to provide an instance of that service.
 * </p>
 * <p>
 * The ServcieProvider may always return the same instance, or it may
 * construct a new instance for each request.
 * </p>
 */

public interface BeanContextServiceProvider {

   /**
    * Invoked by <code>BeanContextServices</code>, this method 
    * requests an instance of a
    * service from this <code>BeanContextServiceProvider</code>. 
    * 
    * @param bcs The <code>BeanContextServices</code> associated with this
    * particular request. This parameter enables the
    * <code>BeanContextServiceProvider</code> to distinguish service 
    * requests from multiple sources.
    *
    * @param requestor	 	The object requesting the service
    *
    * @param serviceClass	The service requested
    *
    * @param serviceSelector the service dependent parameter 
    * for a particular service, or <code>null</code> if not applicable.
    * 
    * @return a reference to the requested service
    */
    Object getService(BeanContextServices bcs, Object requestor, Class serviceClass, Object serviceSelector);

    /**
     * Invoked by <code>BeanContextServices</code>, 
     * this method releases a nested <code>BeanContextChild</code>'s 
     * (or any arbitrary object associated with a
     * <code>BeanContextChild</code>) reference to the specified service.
     * 
     * @param bcs the <code>BeanContextServices</code> associated with this
     * particular release request
     *
     * @param requestor the object requesting the service to be released
     * 
     * @param service the service that is to be released
     */
    public void releaseService(BeanContextServices bcs, Object requestor, Object service);

    /**
     * Invoked by <code>BeanContextServices</code>, this method
     * gets the current service selectors for the specified service. 
     * A service selector is a service specific parameter, 
     * typical examples of which could include: a
     * parameter to a constructor for the service implementation class, 
     * a value for a particular service's property, or a key into a 
     * map of existing implementations. 
     *
     * @param bcs           the <code>BeanContextServices</code> for this request
     * @param serviceClass  the specified service
     * @return   the current service selectors for the specified serviceClass
     */
    Iterator getCurrentServiceSelectors(BeanContextServices bcs, Class serviceClass);
}