001    /* PersistentMBean.java -- Interface for beans that should persist.
002       Copyright (C) 2007 Free Software Foundation, Inc.
003    
004    This file is part of GNU Classpath.
005    
006    GNU Classpath is free software; you can redistribute it and/or modify
007    it under the terms of the GNU General Public License as published by
008    the Free Software Foundation; either version 2, or (at your option)
009    any later version.
010    
011    GNU Classpath is distributed in the hope that it will be useful, but
012    WITHOUT ANY WARRANTY; without even the implied warranty of
013    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
014    General Public License for more details.
015    
016    You should have received a copy of the GNU General Public License
017    along with GNU Classpath; see the file COPYING.  If not, write to the
018    Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
019    02110-1301 USA.
020    
021    Linking this library statically or dynamically with other modules is
022    making a combined work based on this library.  Thus, the terms and
023    conditions of the GNU General Public License cover the whole
024    combination.
025    
026    As a special exception, the copyright holders of this library give you
027    permission to link this library with independent modules to produce an
028    executable, regardless of the license terms of these independent
029    modules, and to copy and distribute the resulting executable under
030    terms of your choice, provided that you also meet, for each linked
031    independent module, the terms and conditions of the license of that
032    module.  An independent module is a module which is not derived from
033    or based on this library.  If you modify this library, you may extend
034    this exception to your version of the library, but you are not
035    obligated to do so.  If you do not wish to do so, delete this
036    exception statement from your version. */
037    
038    package javax.management;
039    
040    /**
041     * Beans may implement this interface in order to become
042     * persistent.  The {@link #load()} method should be
043     * called on construction in order to reload the stored
044     * state.  The {@link #store()} method should be called
045     * sometime during the bean's lifetime in order to create
046     * a persistent copy of the bean's instance data.  This
047     * method may also be called by the {@link MBeanServer}
048     * as a result of the {@link Descriptor} of an
049     * {@link javax.management.modelmbean.ModelMBean}.
050     *
051     * @author Andrew John Hughes (gnu_andrew@member.fsf.org)
052     * @since 1.5
053     */
054    public interface PersistentMBean
055    {
056    
057      /**
058       * Instantiates the bean with the data previously stored
059       * using a call to {@link #store()}.  The data stored can
060       * include values held by attributes as well as those returned
061       * by operations.  This method should be called during
062       * construction or initialisation of the bean, before
063       * it becomes registered with an {@link MBeanServer}.
064       *
065       * @throws MBeanException if persistence is not supported,
066       *                        or another exception is thrown
067       *                        (which this then wraps).
068       * @throws RuntimeOperationsException if the persistence
069       *                                    mechanism throws an
070       *                                    exception.
071       * @throws InstanceNotFoundException if the bean can not
072       *                                   be found in the
073       *                                   persistent store.
074       */
075      void load()
076        throws MBeanException, RuntimeOperationsException,
077               InstanceNotFoundException;
078    
079      /**
080       * <p>
081       * Captures the current state of the bean and stores it
082       * for future retrieval by the {@link #load()} method.
083       * The data stored can include values held by attributes
084       * as well as those returned by operations.
085       * </p>
086       * <p>
087       * Whether the state is stored or not depends on the
088       * <code>persistPolicy</code> field of the MBean/attribute
089       * descriptor.  The state should be stored if the policy
090       * is set to any of the following:
091       * </p>
092       * <ul>
093       * <li><code>always</code></li>
094       * <li><code>onTimer</code> and <code>now</code> is
095       * greater than or equal to <code>lastPersistTime +
096       * persistPeriod</code>.</li>
097       * <li><code>noMoreOftenThan</code> and <code>now</code> is
098       * greater than or equal to <code>lastPersistTime +
099       * persistPeriod</code>.</li>
100       * <li>onUnregister</li>
101       * </ul>
102       * <p>If the policy is set to any of the following, the state
103       * should not be stored:</p>
104       * <ul>
105       * <li><code>never</code></li>
106       * <li><code>onUpdate</code></li>
107       * <li><code>onTimer</code> and <code>now</code> is
108       * less than <code>lastPersistTime + persistPeriod</code>.
109       * </li>
110       * </ul>
111       *
112       * @throws MBeanException if persistence is not supported,
113       *                        or another exception is thrown
114       *                        (which this then wraps).
115       * @throws RuntimeOperationsException if the persistence
116       *                                    mechanism throws an
117       *                                    exception.
118       * @throws InstanceNotFoundException if the persistent
119       *                                   store can not be found
120       *                                   or accessed.
121       */
122      void store()
123        throws MBeanException, RuntimeOperationsException,
124               InstanceNotFoundException;
125    
126    }