001/* A subscriber to exceptions that are handled by CatchExceptionAttribute.
002
003 Copyright (c) 2014 The Regents of the University of California.
004 All rights reserved.
005 Permission is hereby granted, without written agreement and without
006 license or royalty fees, to use, copy, modify, and distribute this
007 software and its documentation for any purpose, provided that the above
008 copyright notice and the following two paragraphs appear in all copies
009 of this software.
010
011 IN NO EVENT SHALL THE UNIVERSITY OF CALIFORNIA BE LIABLE TO ANY PARTY
012 FOR DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES
013 ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN IF
014 THE UNIVERSITY OF CALIFORNIA HAS BEEN ADVISED OF THE POSSIBILITY OF
015 SUCH DAMAGE.
016
017 THE UNIVERSITY OF CALIFORNIA SPECIFICALLY DISCLAIMS ANY WARRANTIES,
018 INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
019 MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE SOFTWARE
020 PROVIDED HEREUNDER IS ON AN "AS IS" BASIS, AND THE UNIVERSITY OF
021 CALIFORNIA HAS NO OBLIGATION TO PROVIDE MAINTENANCE, SUPPORT, UPDATES,
022 ENHANCEMENTS, OR MODIFICATIONS.
023
024 PT_COPYRIGHT_VERSION_2
025 COPYRIGHTENDKEY
026
027 */
028
029package ptolemy.actor.lib;
030
031//////////////////////////////////////////////////////////////////////////
032//// ExceptionSubscriber
033
034/**
035 * An ExceptionSubscriber is an entity that is informed of exceptions and the
036 * handling policy for exceptions caught by
037 * {@link ptolemy.actor.lib.CatchExceptionAttribute}.
038 * The ExceptionSubscriber can then take some action, if desired.
039 * For example, actors that communicate with outside clients may want to pass
040 * along information about the error that has occurred, instead of returning
041 * a generic message or a timeout error response.
042 *
043 * This follows the Command design pattern, where the invoker is
044 * {@link ptolemy.actor.lib.CatchExceptionAttribute}, the client is
045 * the Ptolemy developer (defines commands by dragging and dropping
046 * attributes into the model), and the receiver is a Ptolemy entity
047 * (such as an attribute that writes to a file.
048 *
049 * @author Elizabeth Latronico
050 * @version $Id: ExceptionSubscriber.java 69467 2014-06-29 14:35:19Z beth@berkeley.edu$
051 * @since Ptolemy II 10.0
052 * @Pt.ProposedRating Red (beth)
053 * @Pt.AcceptedRating Red (beth)
054 * @see ptolemy.actor.lib.CatchExceptionAttribute
055 */
056
057public interface ExceptionSubscriber {
058    /** Invoked by an exception handler (e.g. {@link ptolemy.actor.lib.ExceptionManager}) when an
059     *  exception occurs.  Some subscribers may need to set up access to
060     *  resources (such as opening a file) prior to being notified of an
061     *  exception. These could extend AbstractInitalizableAttribute to do so.
062     *
063     * @param policy  The exception handling policy (for example, restart) of
064     * the exception handler; see {@link ptolemy.actor.lib.CatchExceptionAttribute}
065     */
066
067    /** Action to execute upon the occurrence of an exception.
068     *  Some ExceptionReactions may need to set up and close access to resources
069     *  (such as opening and closing a file).  These could extend
070     *  AbstractInitalizableAttribute to do so.
071     *
072     * @param policy The handling policy of the exception manager (for example,
073     *  restart); see {@link ptolemy.actor.lib.CatchExceptionAttribute}
074     * @param exception The exception
075     * @return True if the subscriber successfully processed the information;
076     *  false otherwise (for example, an ExceptionEmailer that fails to send
077     *  an email)
078     */
079
080    public boolean exceptionOccurred(String policy, Throwable exception);
081
082    /** Invoked by an exception handler (e.g. {@link ptolemy.actor.lib.ExceptionManager}) after
083     *  an exception has been handled.
084     *
085     * @param successful True if the exception was successfully handled; false
086     * otherwise
087     * @param message A status message from the exception handler
088     * @return True if the subscriber successfully processed the information;
089     *  false otherwise (for example, an ExceptionEmailer that fails to send
090     *  an email)
091     */
092    public boolean exceptionHandled(boolean successful, String message);
093}