/* PersistentMBean.java -- Interface for beans that should persist.
   Copyright (C) 2007 Free Software Foundation, Inc.

This file is part of GNU Classpath.

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permission to link this library with independent modules to produce an
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package javax.management;

/**
 * Beans may implement this interface in order to become
 * persistent.  The {@link #load()} method should be
 * called on construction in order to reload the stored
 * state.  The {@link #store()} method should be called
 * sometime during the bean's lifetime in order to create
 * a persistent copy of the bean's instance data.  This
 * method may also be called by the {@link MBeanServer}
 * as a result of the {@link Descriptor} of an
 * {@link javax.management.modelmbean.ModelMBean}.
 *
 * @author Andrew John Hughes (gnu_andrew@member.fsf.org)
 * @since 1.5
 */
public interface PersistentMBean
{

  /**
   * Instantiates the bean with the data previously stored
   * using a call to {@link #store()}.  The data stored can
   * include values held by attributes as well as those returned
   * by operations.  This method should be called during
   * construction or initialisation of the bean, before
   * it becomes registered with an {@link MBeanServer}.
   *
   * @throws MBeanException if persistence is not supported,
   *                        or another exception is thrown
   *                        (which this then wraps).
   * @throws RuntimeOperationsException if the persistence
   *                                    mechanism throws an
   *                                    exception.
   * @throws InstanceNotFoundException if the bean can not
   *                                   be found in the
   *                                   persistent store.
   */
  void load()
    throws MBeanException, RuntimeOperationsException,
           InstanceNotFoundException;

  /**
   * <p>
   * Captures the current state of the bean and stores it
   * for future retrieval by the {@link #load()} method.
   * The data stored can include values held by attributes
   * as well as those returned by operations.
   * </p>
   * <p>
   * Whether the state is stored or not depends on the
   * <code>persistPolicy</code> field of the MBean/attribute
   * descriptor.  The state should be stored if the policy
   * is set to any of the following:
   * </p>
   * <ul>
   * <li><code>always</code></li>
   * <li><code>onTimer</code> and <code>now</code> is
   * greater than or equal to <code>lastPersistTime +
   * persistPeriod</code>.</li>
   * <li><code>noMoreOftenThan</code> and <code>now</code> is
   * greater than or equal to <code>lastPersistTime +
   * persistPeriod</code>.</li>
   * <li>onUnregister</li>
   * </ul>
   * <p>If the policy is set to any of the following, the state
   * should not be stored:</p>
   * <ul>
   * <li><code>never</code></li>
   * <li><code>onUpdate</code></li>
   * <li><code>onTimer</code> and <code>now</code> is
   * less than <code>lastPersistTime + persistPeriod</code>.
   * </li>
   * </ul>
   *
   * @throws MBeanException if persistence is not supported,
   *                        or another exception is thrown
   *                        (which this then wraps).
   * @throws RuntimeOperationsException if the persistence
   *                                    mechanism throws an
   *                                    exception.
   * @throws InstanceNotFoundException if the persistent
   *                                   store can not be found
   *                                   or accessed.
   */
  void store()
    throws MBeanException, RuntimeOperationsException,
           InstanceNotFoundException;

}