| /* ExpirableObject.java -- an object that is automatically destroyed. |
| Copyright (C) 2004, 2006 Free Software Foundation, Inc. |
| |
| This file is a 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 |
| the Free Software Foundation; either version 2 of the License, or (at |
| your option) any later version. |
| |
| GNU Classpath 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 for more details. |
| |
| You should have received a copy of the GNU General Public License |
| along with GNU Classpath; if not, write to the Free Software |
| Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 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 |
| conditions of the GNU General Public License cover the whole |
| combination. |
| |
| As a special exception, the copyright holders of this library give you |
| permission to link this library with independent modules to produce an |
| executable, regardless of the license terms of these independent |
| modules, and to copy and distribute the resulting executable under |
| terms of your choice, provided that you also meet, for each linked |
| independent module, the terms and conditions of the license of that |
| module. An independent module is a module which is not derived from |
| or based on this library. If you modify this library, you may extend |
| this exception to your version of the library, but you are not |
| obligated to do so. If you do not wish to do so, delete this |
| exception statement from your version. */ |
| |
| |
| package gnu.java.security.util; |
| |
| import java.util.Timer; |
| import java.util.TimerTask; |
| |
| import javax.security.auth.DestroyFailedException; |
| import javax.security.auth.Destroyable; |
| |
| /** |
| * The base class for objects with sensitive data that are automatically |
| * destroyed after a timeout elapses. On creation, an object that extends this |
| * class will automatically be added to a {@link Timer} object that, once a |
| * timeout elapses, will automatically call the {@link Destroyable#destroy()} |
| * method. |
| * <p> |
| * Concrete subclasses must implement the {@link #doDestroy()} method instead of |
| * {@link Destroyable#destroy()}; the behavior of that method should match |
| * exactly the behavior desired of <code>destroy()</code>. |
| * <p> |
| * Note that if a {@link DestroyFailedException} occurs when the timeout |
| * expires, it will not be reported. |
| * |
| * @see Destroyable |
| */ |
| public abstract class ExpirableObject |
| implements Destroyable |
| { |
| /** |
| * The default timeout, used in the default constructor. |
| */ |
| public static final long DEFAULT_TIMEOUT = 3600000L; |
| |
| /** |
| * The timer that expires instances. |
| */ |
| private static final Timer EXPIRER = new Timer(true); |
| |
| /** |
| * A reference to the task that will destroy this object when the timeout |
| * expires. |
| */ |
| private final Destroyer destroyer; |
| |
| /** |
| * Create a new expirable object that will expire after one hour. |
| */ |
| protected ExpirableObject() |
| { |
| this(DEFAULT_TIMEOUT); |
| } |
| |
| /** |
| * Create a new expirable object that will expire after the specified timeout. |
| * |
| * @param delay The delay before expiration. |
| * @throws IllegalArgumentException If <i>delay</i> is negative, or if |
| * <code>delay + System.currentTimeMillis()</code> is negative. |
| */ |
| protected ExpirableObject(final long delay) |
| { |
| destroyer = new Destroyer(this); |
| EXPIRER.schedule(destroyer, delay); |
| } |
| |
| /** |
| * Destroys this object. This method calls {@link #doDestroy}, then, if no |
| * exception is thrown, cancels the task that would destroy this object when |
| * the timeout is reached. |
| * |
| * @throws DestroyFailedException If this operation fails. |
| */ |
| public final void destroy() throws DestroyFailedException |
| { |
| doDestroy(); |
| destroyer.cancel(); |
| } |
| |
| /** |
| * Subclasses must implement this method instead of the {@link |
| * Destroyable#destroy()} method. |
| * |
| * @throws DestroyFailedException If this operation fails. |
| */ |
| protected abstract void doDestroy() throws DestroyFailedException; |
| |
| /** |
| * The task that destroys the target when the timeout elapses. |
| */ |
| private final class Destroyer |
| extends TimerTask |
| { |
| private final ExpirableObject target; |
| |
| Destroyer(final ExpirableObject target) |
| { |
| super(); |
| this.target = target; |
| } |
| |
| public void run() |
| { |
| try |
| { |
| if (! target.isDestroyed()) |
| target.doDestroy(); |
| } |
| catch (DestroyFailedException dfe) |
| { |
| } |
| } |
| } |
| } |