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.

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permission to link this library with independent modules to produce an
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package java.beans.beancontext;

import java.util.Iterator;
import java.util.TooManyListenersException;

/**
 * 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 1.2
 */

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.
   */
  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.
   */
  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)
   */
  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>.
   */
  Object getService (BeanContextChild requestorChild, Object requestor,
                            Class serviceClass, Object serviceSelector,
                            BeanContextServiceRevokedListener listener)
    throws TooManyListenersException;

  /**
   * 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
   */
  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>.
   */
  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 available.
   */
  boolean hasService (Class serviceClass);

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