/*

 * Copyright (c) 1997, 2004, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

package java.security;

/**

 * A GuardedObject is an object that is used to protect access to

 * another object.

 *

 * <p>A GuardedObject encapsulates a target object and a Guard object,

 * such that access to the target object is possible

 * only if the Guard object allows it.

 * Once an object is encapsulated by a GuardedObject,

 * access to that object is controlled by the <code>getObject</code>

 * method, which invokes the

 * <code>checkGuard</code> method on the Guard object that is

 * guarding access. If access is not allowed,

 * an exception is thrown.

 *

 * @see Guard

 * @see Permission

 *

 * @author Roland Schemers

 * @author Li Gong

 */

public class GuardedObject implements java.io.Serializable {

    private static final long serialVersionUID = -5240450096227834308L;

    private Object object; // the object we are guarding

    private Guard guard;   // the guard

    /**

     * Constructs a GuardedObject using the specified object and guard.

     * If the Guard object is null, then no restrictions will

     * be placed on who can access the object.

     *

     * @param object the object to be guarded.

     *

     * @param guard the Guard object that guards access to the object.

     */

    public GuardedObject(Object object, Guard guard)

    {

        this.guard = guard;

        this.object = object;

    }

    /**

     * Retrieves the guarded object, or throws an exception if access

     * to the guarded object is denied by the guard.

     *

     * @return the guarded object.

     *

     * @exception SecurityException if access to the guarded object is

     * denied.

     */

    public Object getObject()

        throws SecurityException

    {

        if (guard != null)

            guard.checkGuard(object);

        return object;

    }

    /**

     * Writes this object out to a stream (i.e., serializes it).

     * We check the guard if there is one.

     */

    private void writeObject(java.io.ObjectOutputStream oos)

        throws java.io.IOException

    {

        if (guard != null)

            guard.checkGuard(object);

        oos.defaultWriteObject();

    }

}