gcc/libjava/java/beans/beancontext/BeanContextServices.java

/* java.beans.beancontext.BeanContextServices
   Copyright (C) 1999 Free Software Foundation, Inc.

This file is part of GNU Classpath.

GNU Classpath is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
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02111-1307 USA.

Linking this library statically or dynamically with other modules is
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permission to link this library with independent modules to produce an
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independent module, the terms and conditions of the license of that
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this exception to your version of the library, but you are not
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exception statement from your version. */


package java.beans.beancontext;

import java.util.Iterator;

/**
 * Allows a <code>BeanContext</code> to provide services to its children.
 *
 * @specnote it is unclear whether a <code>BeanContextServices</code>
 *           should delegate unhandled requests to parents.  I assume so.
 * @author John Keiser
 * @since JDK1.2
 */

public interface BeanContextServices extends BeanContext, BeanContextServicesListener {
	/**
	 * Register a service to make it available to others.
	 * This class may refuse to add the service based on whatever
	 * information it can gather, including whether the service
	 * provider is trusted.
	 *
	 * @param serviceClass the service class.
	 * @param provider the factory that will actually provide the service.
	 * @return whether the service was added or not.
	 */
	public boolean addService(Class serviceClass, BeanContextServiceProvider provider);

	/**
	 * Make it so that no one else can use this service.
	 * <P>
	 *
	 * If <code>revokeNow</code> is <code>false</code>, the only
	 * effect of this method is to make all subsequent calls to
	 * <code>getService()</code> on this service class fail.
	 * <P>
	 *
	 * If it is <code>true</code>, a message is also sent out to all
	 * listeners on the service and all references to it are released.
	 *
	 * @param serviceClass the service class to revoke.
	 * @param provider the service provider providing the service class.
	 * @param revokeNow whether to release all current references to
	 *        the service.
	 */
	public void revokeService(Class serviceClass, BeanContextServiceProvider provider, boolean revokeNow);

	/**
	 * Release your copy of this service.
	 * <P>
	 *
	 * If all copies of the service's class have been relinquished by
	 * the requestor, the <code>BeanContextServiceRevokedListener</code>
	 * previously registered by <code>getService()</code> will be
	 * unregistered.
	 *
	 * @param requestorChild the original <code>BeanContextChild</code>
	 *        requesting the service.
	 * @param requestor the original requestor of the service.
	 * @param service the service to relinquish
	 * @see #getService(java.beans.beancontext.BeanContextChild,java.lang.Object,java.lang.Class,java.lang.Object,java.beans.beancontext.BeanContextServiceRevokedListener)
	 */
	public void releaseService(BeanContextChild requestorChild, Object requestor, Object service);

	/**
	 * Get a service from this <code>BeanContextServices</code>.
	 * <P>
	 *
	 * The specified listener will be registered to receive a
	 * revocation notice for the specified serviceClass.  One
	 * notification per service class per requestor object will be
	 * sent.
	 * <P>
	 *
	 * The listener will be unregistered when all services that were
	 * obtained by that requestor for that service class are released.
	 * <P>
	 *
	 * If the requested service class is not available, or if this
	 * <code>BeanContextServices</code> object chooses not honor the
	 * request because the service class has been revoked or for some
	 * other reason, then this method will return <code>null</code>.
	 * <P>
	 *
	 * This method may throw unchecked exceptions, so watch out.
	 *
	 * @specnote it is not specified what happens when two subsequent
	 *           calls are made to <code>getService()</code> with the
	 *           same requestor object and service class but different
	 *           listeners.  Which listener is to be notified?
	 *
	 * @param requestorChild the <code>BeanContextChild</code>
	 *        associated with the requestor.  Typically this will be
	 *        the same as the requestor itself, but since any
	 *        <code>Object</code>, even one outside the hierarchy, may
	 *        make a request, this parameter is necessary.  Only weak
	 *        references to this will be retained, and it will never
	 *        be changed, only queried in a read-only manner.
	 * @param requestor the actual requestor of the service.  Only
	 *        weak references to this will be retained, and it will
	 *        never be changed, only queried in a read-only manner.
	 * @param serviceClass the <code>Class</code> of the service being
	 *        requested.
	 * @param serviceSelector a parameter to customize the service
	 *        returned with.
	 * @param listener a listener that will be notified if the service
	 *        being requested is revoked.
	 * @return an instance of <code>serviceClass</code> (such that
	 *        <code>instanceof</code> serviceClass is true), or
	 *        <code>null</code>.
	 */
	public Object getService(BeanContextChild requestorChild, Object requestor, Class serviceClass, Object serviceSelector, BeanContextServiceRevokedListener listener);

	/**
	 * Get a list of all service classes supported.
	 * <P>
	 *
	 * This method must synchronize on
	 * <code>BeanContext.globalHierarchyLock</code>.
	 *
	 * @return a list of all service classes supported.
	 * @see java.beans.beancontext.BeanContext#globalHierarchyLock
	 */
	public Iterator getCurrentServiceClasses();

	/**
	 * Get a list of valid service selectors for the specified service class.
	 * <P>
	 *
	 * If the specified service class does not have a finite number of
	 * valid service selectors, it should return <code>null</code>.
	 * If it takes a general <code>Integer</code> parameter, for
	 * example, you may as well return <code>null</code> or the poor
	 * soul who called this method will be iterating all day.
	 * <P>
	 *
	 * If it has no valid service selectors, it should still return an empty
	 * <code>Iterator</code>.
	 *
	 * @param serviceClass the service class to get selectors for.
	 * @return a list of valid service selectors for the service
	 *         class, or <code>null</code>.
	 */
	public Iterator getCurrentServiceSelectors(Class serviceClass);

	/**
	 * Tell whether the specified service class is available.
	 * Iff getService() could return a non-null value for the
	 * specified service, this method will return <code>true</code>.
	 *
	 * @param serviceClass the service class to check on.
	 * @return whether the specified service class is availabe.
	 */
	public boolean hasService(Class serviceClass);

	/**
	 * Add a listener on all adds and removes of services.
	 * @param listener the listener to add.
	 */
	public void addBeanContextServicesListener(BeanContextServicesListener listener);

	/**
	 * Remove a listener on all adds and removes of services.
	 * @specnote it is not certain whether this should remove this
	 *           listener if it was specified in
	 *           <code>getService()</code>.
	 * @param listener the listener to add.
	 */
	public void removeBeanContextServicesListener(BeanContextServicesListener listener);
}