001/* MemoryNotificationInfo.java - Emitted memory notification info.
002   Copyright (C) 2006 Free Software Foundation
003
004This file is part of GNU Classpath.
005
006GNU Classpath is free software; you can redistribute it and/or modify
007it under the terms of the GNU General Public License as published by
008the Free Software Foundation; either version 2, or (at your option)
009any later version.
010
011GNU Classpath is distributed in the hope that it will be useful, but
012WITHOUT ANY WARRANTY; without even the implied warranty of
013MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
014General Public License for more details.
015
016You should have received a copy of the GNU General Public License
017along with GNU Classpath; see the file COPYING.  If not, write to the
018Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
01902110-1301 USA.
020
021Linking this library statically or dynamically with other modules is
022making a combined work based on this library.  Thus, the terms and
023conditions of the GNU General Public License cover the whole
024combination.
025
026As a special exception, the copyright holders of this library give you
027permission to link this library with independent modules to produce an
028executable, regardless of the license terms of these independent
029modules, and to copy and distribute the resulting executable under
030terms of your choice, provided that you also meet, for each linked
031independent module, the terms and conditions of the license of that
032module.  An independent module is a module which is not derived from
033or based on this library.  If you modify this library, you may extend
034this exception to your version of the library, but you are not
035obligated to do so.  If you do not wish to do so, delete this
036exception statement from your version. */
037
038package java.lang.management;
039
040import gnu.java.lang.management.MemoryMXBeanImpl;
041
042import javax.management.openmbean.CompositeData;
043import javax.management.openmbean.CompositeType;
044import javax.management.openmbean.SimpleType;
045
046/**
047 * <p>
048 * Represents the content of a notification emitted by the
049 * {@link MemoryMXBean}.  Such notifications are emitted when
050 * one of the memory pools exceeds its usage or collection
051 * usage threshold.  This object contains the following information,
052 * representing the state of the pool at the time of the
053 * notification:
054 * </p>
055 * <ul>
056 * <li>The name of the pool.</li>
057 * <li>The memory usage of the pool at the time of notification.</li>
058 * <li>The number of times the pool has exceeded this particular
059 * threshold in the past.</li>
060 * </ul>
061 * <p>
062 * Two types of notification are emitted by the {@link MemoryMXBean}:
063 * one for exceeding the usage threshold and one for exceeding the
064 * collection usage threshold.  The value returned by {@link #getCount()}
065 * is dependent on this type; if the threshold exceeded is the usage
066 * threshold, then the usage threshold count is returned.  If, instead,
067 * the collection usage threshold is exceeded, then the collection usage
068 * threshold count is returned.
069 * </p>
070 * <p>
071 * This data is held in the user data part of the notification (returned
072 * by {@link javax.management.Notification#getUserData()}) encapsulated in
073 * a {@link javax.management.openmbean.CompositeData} object.  The
074 * {@link #from(javax.management.openmbean.CompositeData)} method may be
075 * used to unwrap the value and obtain an instance of this class.
076 * </p>
077 *
078 * @author Andrew John Hughes (gnu_andrew@member.fsf.org)
079 * @since 1.5
080 */
081public class MemoryNotificationInfo
082{
083
084  /**
085   * The type of notification emitted when the usage threshold is exceeded.
086   * After a notification is emitted, the usage level must drop below the
087   * threshold again before another notification is emitted.  The value is
088   * <code>java.management.memory.threshold.exceeded</code>.
089   */
090  public static final String MEMORY_THRESHOLD_EXCEEDED =
091    "java.management.memory.threshold.exceeded";
092
093  /**
094   * The type of notification emitted when the collection usage threshold
095   * is exceeded, following a garbage collection cycle.  The value is
096   * <code>java.management.memory.collection.threshold.exceeded</code>.
097   */
098  public static final String MEMORY_COLLECTION_THRESHOLD_EXCEEDED =
099    "java.management.memory.collection.threshold.exceeded";
100
101  /**
102   * The name of the memory pool which exceeded the threshold.
103   */
104  private String poolName;
105
106  /**
107   * The usage level of the memory pool at the time of notification.
108   */
109  private MemoryUsage usage;
110
111  /**
112   * The number of times the threshold has been crossed.
113   */
114  private long count;
115
116  /**
117   * Constructs a new {@link MemoryNotificationInfo} object using the
118   * specified pool name, usage level and threshold crossing count.
119   *
120   * @param poolName the name of the pool which has exceeded a threshold.
121   * @param usage the usage level of the pool at the time of notification.
122   * @param count the number of times the threshold has been crossed.
123   */
124  public MemoryNotificationInfo(String poolName, MemoryUsage usage, long count)
125  {
126    this.poolName = poolName;
127    this.usage = usage;
128    this.count = count;
129  }
130
131  /**
132   * <p>
133   * Returns a {@link MemoryNotificationInfo} instance using the values
134   * given in the supplied
135   * {@link javax.management.openmbean.CompositeData} object.
136   * The composite data instance should contain the following
137   * attributes with the specified types:
138   * </p>
139   * <table>
140   * <th><td>Name</td><td>Type</td></th>
141   * <tr><td>poolName</td><td>java.lang.String</td></tr>
142   * <tr><td>usage</td><td>javax.management.openmbean.CompositeData
143   * </td></tr>
144   * <tr><td>count</td><td>java.lang.Long</td></tr>
145   * </table>
146   * <p>
147   * The usage level is further described as:
148   * </p>
149   * <table>
150   * <th><td>Name</td><td>Type</td></th>
151   * <tr><td>init</td><td>java.lang.Long</td></tr>
152   * <tr><td>used</td><td>java.lang.Long</td></tr>
153   * <tr><td>committed</td><td>java.lang.Long</td></tr>
154   * <tr><td>max</td><td>java.lang.Long</td></tr>
155   * </table>
156   *
157   * @param data the composite data structure to take values from.
158   * @return a new instance containing the values from the
159   *         composite data structure, or <code>null</code>
160   *         if the data structure was also <code>null</code>.
161   * @throws IllegalArgumentException if the composite data structure
162   *                                  does not match the structure
163   *                                  outlined above.
164   */
165  public static MemoryNotificationInfo from(CompositeData data)
166  {
167    if (data == null)
168      return null;
169    CompositeType type = data.getCompositeType();
170    ThreadInfo.checkAttribute(type, "poolName", SimpleType.STRING);
171    ThreadInfo.checkAttribute(type, "usage", MemoryMXBeanImpl.usageType);
172    ThreadInfo.checkAttribute(type, "count", SimpleType.LONG);
173    MemoryUsage usage = MemoryUsage.from((CompositeData) data.get("usage"));
174    return new MemoryNotificationInfo(((String) data.get("poolName")),
175                                      usage,
176                                      ((Long) data.get("count")).longValue());
177  }
178
179  /**
180   * Returns the number of times the memory pool has crossed the usage
181   * threshold, as of the time of notification.  If this is the notification
182   * represented by the type {@link #MEMORY_THRESHOLD_EXCEEDED}, then the
183   * count is the usage threshold count.  If this is the notification
184   * represented by the type {@link #MEMORY_COLLECTION_THRESHOLD_EXCEEDED},
185   * then the count is the collection usage threshold count.
186   *
187   * @return the number of times the appropriate threshold has been crossed.
188   */
189  public long getCount()
190  {
191    return count;
192  }
193
194  /**
195   * Returns the name of the pool which has crossed a threshold.
196   *
197   * @return the name of the pool.
198   */
199  public String getPoolName()
200  {
201    return poolName;
202  }
203
204  /**
205   * Returns the usage levels at the time of notification.
206   *
207   * @return the usage levels.
208   */
209  public MemoryUsage getUsage()
210  {
211    return usage;
212  }
213
214}