source: trunk/gcc/libjava/java/beans/beancontext/BeanContext.java

/* java.beans.beancontext.BeanContext
   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.Collection;
import java.beans.Visibility;
import java.beans.DesignMode;
import java.net.URL;
import java.io.InputStream;
import java.io.IOException;

/**
 * Acts as a container for sub-beans and as a sub-bean,
 * so that an entire hierarchy of beans can be made up of
 * <code>BeanContext</code>s.
 * <P>
 *
 * Since I can't sprinkle the <code>Collections</code> interface
 * documentation with special information for <code>BeanContext</code>
 * implementors, I'll have to document special requirements for
 * implementors of those functions here.
 * <P>
 *
 * <code><strong>add()</strong></code> or <code>addAll()</code>:
 * <br>
 * <OL>
 *   <LI>
 *     May add any <code>Object</code> into the hierarchy as well as a
 *     <code>BeanContextChild</code>, <code>BeanContext</code> or
 *     <code>BeanContextProxy</code> object.
 *     This way, any Bean can be in the hierarchy.
 *   </LI>
 *   <LI>
 *     Must synchronize on <code>BeanContext.globalHierarchyLock</code>.
 *   </LI>
 *   <LI>
 *     Don't add the <code>Object</code> if it's already there (only once
 *     per <code>BeanContext</code>).
 *   </LI>
 *   <LI>
 *     If it is a <code>BeanContextChild</code> implementor, call
 *     <code>setBeanContext()</code> on it.  If it's a
 *     <code>BeanContextProxy</code> implementor, call
 *     <code>getBeanContextProxy().setBeanContext()</code> on it.
 *     If <code>setBeanContext()</code> vetoes the change, back out
 *     all changes so far and throw <code>IllegalStateException</code>.
 *   </LI>
 *   <LI>
 *     If it (or its proxy) implements <code>Visibility</code>, call
 *     <code>dontUseGui()</code> or <code>okToUseGui()</code> on it,
 *     depending on whether you (the <code>BeanContext</code>) feel like
 *     allowing it to use the GUI or not.
 *   </LI>
 *   <LI>
 *     If it implements <code>BeanContextChild</code> or
 *     <code>BeanContextProxy</code>, register yourself (the
 *     <code>BeanContext</code>) as both a
 *     <code>PropertyChangeListener</code> and
 *     <code>VetoableChangeListener</code> on the "beanContext"
 *     property (it may also add itself on any other properties it wishes
 *     to).
 *   </LI>
 *   <LI>
 *     If it is a listener or event source that you (the
 *     <code>BeanContext</code>) are interested in, you may register
 *     yourself to it or register it to you.
 *   </LI>
 *   <LI>
 *     Fire a <code>java.beans.beancontext.BeanContextMembershipEvent</code>
 *     before exiting.  <code>addAll()</code> should wait until everything
 *     is done changing before firing the event (or events) so that if a
 *     failure occurs, the backing-out process can proceed without any
 *     events being fired at all.
 *   </LI>
 * </OL>
 * <P>
 *
 * <code><strong>remove()</strong></code> or <code>removeAll()</code>:
 * <br>
 * <OL>
 *   <LI>
 *     Must synchronize on <code>BeanContext.globalHierarchyLock</code>.
 *   </LI>
 *   <LI>
 *     If the specified <code>Object</code> is not a child of this
 *     <code>BeanContext</code>, just exit without performing any actions.
 *   </LI>
 *   <LI>
 *     Remove the <code>Object</code> from your collection of children.
 *   </LI>
 *   <LI>
 *     If it is a <code>BeanContextChild</code> implementor, call
 *     <code>setBeanContext(null)</code> on it.  If it's a
 *     <code>BeanContextProxy</code> implementor, call
 *     <code>getBeanContextProxy().setBeanContext(null)</code> on it.
 *     If <code>setBeanContext()</code> vetoes the change, back out
 *     all changes so far and throw <code>IllegalStateException</code>.
 *   </LI>
 *   <LI>
 *     If you registered the <code>Object</code> to listen to you or
 *     registered yourself as a listener on the <code>Object</code> during
 *     <code>add()</code> or <code>addAll()</code>, undo the registration
 *     bycalling the appropriate <code>removeListener()</code> method.
 *   </LI>
 *   <LI>
 *     Fire a <code>java.beans.beancontext.BeanContextMembershipEvent</code>
 *     before exiting.  <code>removeAll()</code> should wait until
 *     everything is done changing before firing the event (or events) so
 *     that if a failure occurs, the backing-out process can proceed
 *     without any events being fired at all.
 *   </LI>
 * </OL>
 * <P>
 *
 * <code>addAll()</code>, <code>removeAll()</code>,
 * <code>retainAll()</code> and <code>clear()</code> do not need to be
 * implemented, but may be if so desired.
 * <P>
 *
 * Similarly, <code>Visibility</code> and <code>DesignMode</code> methods
 * should propagate changed values to children that implement interfaces
 * of the same name.
 * <P>
 *
 * A hierarchy of beans is mainly useful so that different sets of beans
 * can be established, each with their own set of resources.
 *
 * @author John Keiser
 * @since JDK1.2
 */

public interface BeanContext
        extends Collection, BeanContextChild, Visibility, DesignMode {

        /**
         * The global lock on changing any BeanContext hierarchy.
         * It kinda sucks that there is only one lock, since there can be
         * multiple hierarchies.  Oh well, I didn't design, I just code.
         * <P>
         *
         * Methods that must (or do) synchronize on the global lock:
         * <BR>
         * <UL>
         *   <LI>
         *     Implementors of <CODE>BeanContext.add()</CODE> and <code>addAll()</code>
         *   </LI>
         * </UL>
         * @fixme fill in the rest of the methods which use the global lock.
         */
        public static final Object globalHierarchyLock = new Object();

        /** 
         * Instantiate a Bean using this Bean's <code>ClassLoader</code>
         * and this <code>BeanContext</code> as the parent.
         * <P>
         *
         * This method exists mainly so that <code>BeanContext</code>
         * implementations can perform extra actions on Beans that are
         * created within them.
         *
         * @param beanName the name of the bean to instantiate
         * @return the created Bean
         *
         * @see java.beans.Beans#instantiate(java.lang.ClassLoader,java.lang.String)
         * @see java.beans.Beans#instantiate(java.lang.ClassLoader,java.lang.String,java.lang.BeanContext)
         * @exception IOException if there is an I/O problem during
         *            instantiation.
         * @exception ClassNotFoundException if a serialized Bean's class
         *            is not found.
         */
        public Object instantiateChild(String beanName)
                        throws IOException,
                               ClassNotFoundException;

        /**
         * Get a resource.  The <code>BeanContext</code> will typically
         * call <code>ClassLoader.getResource()</code>, but may do it any
         * way it wants to.  This allows a <code>BeanContext</code> to
         * have its own set of resources separate from the rest of the
         * system.
         * <P>
         *
         * Beans should call this method on their parent rather than the
         * associated <code>ClassLoader</code> method.
         * <P>
         *
         * I am assuming, but am not entirely sure, that if a
         * <code>BeanContext</code> cannot find a resource, its
         * responsibility is to call the <code>getResource</code> method
         * of its parent <code>BeanContext</code>.
         *
         * @return a URL to the requested resource.
         * @param resourceName the name of the resource requested.
         * @param requestor a reference to the child requesting the resource.
         * @see java.lang.ClassLoader#getResource(java.lang.String)
         */
        public URL getResource(String resourceName, BeanContextChild requestor);

        /**
         * Get a resource as a stream.  The <code>BeanContext</code> will
         * typically call <code>ClassLoader.getResourceAsStream()</code>,
         * but may do it any way it wants to.  This allows a
         * <code>BeanContext</code>'s children to have their own set of
         * resources separate from the rest of the system.
         * <P>
         *
         * Beans should call this method on their parent rather than the
         * associated <code>ClassLoader</code> method.
         * <P>
         *
         * I am assuming, but am not entirely sure, that if a
         * <code>BeanContext</code> cannot find a resource, its
         * responsibility is to call the <code>getResourceAsStream</code>
         * method of its parent <code>BeanContext</code>.
         *
         * @return the requested resource as a stream.
         * @param resourceName the name of the resource requested.
         * @param requestor a reference to the child requesting the resource.
         * @see java.lang.ClassLoader#getResourceAsStream(java.lang.String)
         */
        public InputStream getResourceAsStream(String resourceName, BeanContextChild requestor);

        /**
         * Add a listener on changes to the membership of this
         * <code>BeanContext</code> object.
         * @param listener the listener to add.
         */
        public void addBeanContextMembershipListener(BeanContextMembershipListener listener);

        /**
         * Remove a listener on changes to the membership of this
         * <code>BeanContext</code> object.
         * @param listener the listener to remove.
         */
        public void removeBeanContextMembershipListener(BeanContextMembershipListener listener);
}