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authorupstream source tree <ports@midipix.org>2015-03-15 20:14:05 -0400
committerupstream source tree <ports@midipix.org>2015-03-15 20:14:05 -0400
commit554fd8c5195424bdbcabf5de30fdc183aba391bd (patch)
tree976dc5ab7fddf506dadce60ae936f43f58787092 /libjava/classpath/gnu/java/security/util/ExpirableObject.java
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+/* 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)
+ {
+ }
+ }
+ }
+}