gcc/libjava/classpath/java/beans/beancontext/BeanContextServiceProvider.java

/* java.beans.beancontext.BeanContextServiceProvider
   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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any later version.
 
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02110-1301 USA.

Linking this library statically or dynamically with other modules is
making a combined work based on this library.  Thus, the terms and
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permission to link this library with independent modules to produce an
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modules, and to copy and distribute the resulting executable under
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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;

/**
 * An actual factory for services.
 * <P>
 *
 * It is the <code>BeanContextServiceProvider</code>'s responsibility to
 * register itself with whatever <code>BeanContextServices</code> object
 * it wishes to provide services through using the
 * <code>addService()</code> method.
 * <P>
 *
 * If for some reason it can no longer provide services for a particular
 * class, this class must invoke
 * <code>BeanContextServices.revokeService(serviceClass,this,true)</code>
 * for all the places it has registered the service.
 *
 * @author John Keiser
 * @since JDK1.2
 */

public interface BeanContextServiceProvider {
	/**
	 * Get a service.
	 * Called from <code>BeanContextServices.getService()</code>.
	 *
	 * <p>If the requested service class is not available, or if this
	 * <code>BeanContextServiceProvider</code> chooses not honor the
	 * request for some reason, then this method will return
	 * <code>null</code>.</p>
	 *
	 * This method may throw unchecked exceptions, so watch out.
	 *
	 * @param services the <code>BeanContextServices</code> that wants
	 *        to get the service.  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.
	 * @return an instance of <code>serviceClass</code> (such that
	 *        <code>instanceof</code> serviceClass is true), or
	 *        <code>null</code>.
	 * @see java.beans.beancontext.BeanContextServices#getService(java.beans.beancontext.BeanContextChild,java.lang.Object,java.lang.Class,java.lang.Object,java.beans.beancontext.BeanContextServiceRevokedListener)
	 */
	Object getService(BeanContextServices services, Object requestor, Class serviceClass, Object serviceSelector);

	/**
	 * Release the service.
	 * <P>
	 *
	 * Called by <code>BeanContextServices.releaseService()</code>.
	 * <P>
	 *
	 * Most <code>BeanContextServiceProvider</code>s won't have to do
	 * anything here.
	 *
	 * @param services the <code>BeanContextServices</code> that wants
	 *        to release the service.  Only weak references to this will
	 *        be retained, and it will never be changed, only queried
	 *        in a read-only manner.
	 * @param requestor the original requestor of the service.
	 * @param service the service to relinquish
	 * @see java.beans.beancontext.BeanContextServices#releaseService(java.beans.beancontext.BeanContextChild,java.lang.Object,java.lang.Object)
	 */
	void releaseService(BeanContextServices services, Object requestor, Object service);

	/**
	 * Get a list of valid service selectors for the specified service class.
	 * This method is called from
	 * <code>BeanContextServices.getCurrentServiceSelectors()</code>.
	 * <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 services the <code>BeanContextServices</code> that wants
	 *        to get the service selectors.  Only weak references to this will
	 *        be retained, and it will never be changed, only queried
	 *        in a read-only manner.
	 * @param serviceClass the service class to get selectors for.
	 * @return a list of valid service selectors for the service
	 *         class, or <code>null</code>.
	 * @see java.beans.beancontext.BeanContextServices#getCurrentServiceSelectors(java.lang.Class)
	 */
	Iterator getCurrentServiceSelectors(BeanContextServices services, Class serviceClass);
}