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jeremybenn |
/* GuardedObject.java -- An object protected by a Guard
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Copyright (C) 1998, 2002, 2004, 2005 Free Software Foundation, Inc.
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This file is part of GNU Classpath.
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GNU Classpath is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2, or (at your option)
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any later version.
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GNU Classpath is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with GNU Classpath; see the file COPYING. If not, write to the
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Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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02110-1301 USA.
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Linking this library statically or dynamically with other modules is
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making a combined work based on this library. Thus, the terms and
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conditions of the GNU General Public License cover the whole
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combination.
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As a special exception, the copyright holders of this library give you
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permission to link this library with independent modules to produce an
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executable, regardless of the license terms of these independent
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modules, and to copy and distribute the resulting executable under
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terms of your choice, provided that you also meet, for each linked
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independent module, the terms and conditions of the license of that
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module. An independent module is a module which is not derived from
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or based on this library. If you modify this library, you may extend
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this exception to your version of the library, but you are not
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obligated to do so. If you do not wish to do so, delete this
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exception statement from your version. */
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package java.security;
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import java.io.IOException;
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import java.io.ObjectOutputStream;
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import java.io.Serializable;
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/**
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* This class is an object that is guarded by a <code>Guard</code> object.
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* The object that is being guarded is retrieved by a call to the only
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* method in this class - <code>getObject</code>. That method returns the
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* guarded <code>Object</code> after first checking with the
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* <code>Guard</code>. If the <code>Guard</code> disallows access, an
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* exception will be thrown.
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*
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* @author Aaron M. Renn (arenn@urbanophile.com)
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* @since 1.1
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* @status updated to 1.4
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*/
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public class GuardedObject implements Serializable
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{
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/**
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* Compatible with JDK 1.1+.
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*/
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private static final long serialVersionUID = -5240450096227834308L;
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/**
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* This is the Guard that is protecting the object.
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*
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* @serial the guard
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*/
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private final Guard guard;
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/**
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* This is the object that is being guarded.
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*
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* @serial the protected object
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*/
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private final Object object;
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/**
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* This method initializes a new instance of <code>GuardedObject</code>
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* that protects the specified <code>Object</code> using the specified
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* <code>Guard</code>. A null guard means there are no restrictions on
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* accessing the object.
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*
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* @param object the <code>Object</code> to guard
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* @param guard the <code>Guard</code> that is protecting the object
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*/
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public GuardedObject(Object object, Guard guard)
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{
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this.object = object;
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this.guard = guard;
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}
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/**
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* This method first call the <code>checkGuard</code> method on the
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* <code>Guard</code> object protecting the guarded object. If the
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* <code>Guard</code> disallows access, an exception is thrown, otherwise
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* the <code>Object</code> is returned.
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*
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* @return The object being guarded
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* @throws SecurityException if access is denied
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*/
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public Object getObject()
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{
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if (guard != null)
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guard.checkGuard(object);
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return object;
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}
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/**
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* Ensures that serialization is legal, by checking the guard.
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*
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* @param s the stream to write to
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* @throws IOException if the underlying stream fails
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*/
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private void writeObject(ObjectOutputStream s) throws IOException
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{
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if (guard != null)
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guard.checkGuard(object);
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s.defaultWriteObject();
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}
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} // class GuardedObject
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