001/* MBeanServerFactory.java -- Manages server instances.
002   Copyright (C) 2006 Free Software Foundation, Inc.
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 javax.management;
039
040import gnu.classpath.SystemProperties;
041
042import java.util.ArrayList;
043import java.util.HashMap;
044import java.util.Iterator;
045import java.util.Map;
046
047import javax.management.loading.ClassLoaderRepository;
048
049/**
050 * <p>
051 * Creates and maintains a set of {@link MBeanServer} instances.
052 * Server instances, as of JMX 1.2, are created using a subclass
053 * of {@link MBeanServerBuilder}.  The exact class used is controlled
054 * by the property <code>javax.management.builder.initial</code>,
055 * and allows the instances created by {@link MBeanServerBuilder}
056 * to be wrapped, thus providing additional functionality.
057 * </p>
058 * <p>
059 * The property is used as follows:
060 * </p>
061 * <ol>
062 * <li>If the property has no value, then an instance of
063 * {@link MBeanServerBuilder} is used.</li>
064 * <li>If a value is given, then:
065 * <ol>
066 * <li>The class is loaded using
067 * <code>Thread.currentThread().getContextClassLoader()</code>, or,
068 * if this is <code>null</code>, by <code>Class.forName()</code>.</li>
069 * <li><code>Class.newInstance()</code> is used to create an instance
070 * of the class.  The class must be public and have a public empty
071 * constructor.  If an exception is thrown, it is propogated as
072 * a {@link JMRuntimeException} and no new server instances may be
073 * created until the property is set to a valid value.</li>
074 * </ol></li>
075 * <li>The value is checked on each successive request for a server.
076 * If it differs from the class of the existing instance of
077 * {@link MBeanServerBuilder}, then the value is used to create
078 * a new instance.</li>
079 * </ol>
080 */
081public class MBeanServerFactory
082{
083
084  /**
085   * The last builder instance.
086   */
087  private static MBeanServerBuilder builder;
088
089  /**
090   * The map of registered servers (identifiers to servers).
091   */
092  private static final Map<Object,MBeanServer> servers =
093    new HashMap<Object,MBeanServer>();
094
095  /**
096   * Private constructor to prevent instance creation.
097   */
098  private MBeanServerFactory() {}
099
100  /**
101   * Returns a server implementation using the default domain name
102   * of <code>"DefaultDomain"</code>.  The default domain name is
103   * used when the domain name specified by the user is <code>null</code.
104   * A reference to the created server is retained, so that it can
105   * be retrieved at a later date using {@link #findMBeanServer}.
106   * Calling this method is equivalent to calling
107   * {@link createMBeanServer(String)} with a <code>null</code> value.
108   *
109   * @return a new {@link MBeanServer} instance.
110   * @throws SecurityException if a security manager exists and the
111   *                           caller's permissions don't imply {@link
112   *                           MBeanServerPermission(String)}("createMBeanServer")
113   * @throws JMRuntimeException if the property
114   *                     <code>javax.management.builder.initial</code>
115   *                     exists but names a class which either can not be
116   *                     instantiated or provides an implementation that returns
117   *                     <code>null</code> from either
118   *                     {@link MBeanServerBuilder#newMBeanServerDelegate()}
119   *                     or {@link MBeanServerBuilder#newMBeanServer()}
120   * @throws ClassCastException if the property
121   *                     <code>javax.management.builder.initial</code>
122   *                     exists but names a class which is not a subclass
123   *                     of {@link MBeanServerBuilder}.
124   * @see #createMBeanServer(String)
125   */
126  public static MBeanServer createMBeanServer()
127  {
128    return createMBeanServer(null);
129  }
130
131  /**
132   * Returns a server implementation using the default domain name
133   * given, or <code>"DefaultDomain"</code> if this is <code>null</code>.
134   * The default domain name is used when the domain name specified by
135   * the user is <code>null</code.  A reference to the created server is
136   * retained, so that it can be retrieved at a later date using
137   * {@link #findMBeanServer}.
138   *
139   * @param domain the default domain name of the server.
140   * @return a new {@link MBeanServer} instance.
141   * @throws SecurityException if a security manager exists and the
142   *                           caller's permissions don't imply {@link
143   *                           MBeanServerPermission(String)}("createMBeanServer")
144   * @throws JMRuntimeException if the property
145   *                     <code>javax.management.builder.initial</code>
146   *                     exists but names a class which either can not be
147   *                     instantiated or provides an implementation that returns
148   *                     <code>null</code> from either
149   *                     {@link MBeanServerBuilder#newMBeanServerDelegate()}
150   *                     or {@link MBeanServerBuilder#newMBeanServer()}
151   * @throws ClassCastException if the property
152   *                     <code>javax.management.builder.initial</code>
153   *                     exists but names a class which is not a subclass
154   *                     of {@link MBeanServerBuilder}.
155   */
156  public static MBeanServer createMBeanServer(String domain)
157  {
158    SecurityManager sm = System.getSecurityManager();
159    if (sm != null)
160      sm.checkPermission(new MBeanServerPermission("createMBeanServer"));
161    MBeanServer server = createServer(domain);
162    try
163      {
164        ObjectName dn = new
165          ObjectName("JMImplementation:type=MBeanServerDelegate");
166        servers.put(server.getAttribute(dn, "MBeanServerId"), server);
167      }
168    catch (MalformedObjectNameException e)
169      {
170        throw (Error)
171          (new InternalError("Malformed delegate bean name.").initCause(e));
172      }
173    catch (MBeanException e)
174      {
175        throw (Error)
176          (new InternalError("Exception in getMBeanServerId().").initCause(e));
177      }
178    catch (AttributeNotFoundException e)
179      {
180        throw (Error)
181          (new InternalError("Could not find MBeanServerId attribute.").initCause(e));
182      }
183    catch (InstanceNotFoundException e)
184      {
185        throw (Error)
186          (new InternalError("Could not find the delegate bean.").initCause(e));
187      }
188    catch (ReflectionException e)
189      {
190        throw (Error)
191          (new InternalError("Could not call getMBeanServerId().").initCause(e));
192      }
193    return server;
194  }
195
196  /**
197   * Returns the specified server, or, if <code>id</code> is <code>null</code>,
198   * a list of all registered servers.  A registered server is one that
199   * was created using {@link #createMBeanServer()} or
200   * {@link #createMBeanServer(String)} and has not yet been released
201   * using {@link releaseMBeanServer(MBeanServer)}.
202   *
203   * @param id the id of the server to retrieve, or <code>null</code>
204   *           to return all servers.
205   * @return a list of {@link MBeanServer}s.
206   * @throws SecurityException if a security manager exists and the
207   *                           caller's permissions don't imply {@link
208   *                           MBeanServerPermission(String)}("findMBeanServer")
209   */
210  public static ArrayList<MBeanServer> findMBeanServer(String id)
211  {
212    SecurityManager sm = System.getSecurityManager();
213    if (sm != null)
214      sm.checkPermission(new MBeanServerPermission("findMBeanServer"));
215    if (id == null)
216      return new ArrayList<MBeanServer>(servers.values());
217    ArrayList<MBeanServer> list = new ArrayList<MBeanServer>();
218    MBeanServer server = servers.get(id);
219    if (server != null)
220      list.add(servers.get(id));
221    return list;
222  }
223
224  /**
225   * Returns the class loader repository used by the specified server.
226   * This is equivalent to calling {@link MBeanServer#getClassLoaderRepository()}
227   * on the given server.
228   *
229   * @param server the server whose class loader repository should be
230   *               retrieved.
231   * @throws NullPointerException if <code>server</code> is <code>null</code>.
232   * @throws SecurityException if a security manager exists and the
233   *                           caller's permissions don't imply {@link
234   *                           MBeanPermission(String,String,ObjectName,String)
235   *                           <code>MBeanPermission(null, null, null,
236   *                           "getClassLoaderRepository")</code>
237   */
238  public static ClassLoaderRepository getClassLoaderRepository(MBeanServer server)
239  {
240    return server.getClassLoaderRepository();
241  }
242
243  /**
244   * Returns a server implementation using the default domain name
245   * of <code>"DefaultDomain"</code>.  The default domain name is
246   * used when the domain name specified by the user is <code>null</code.
247   * No reference to the created server is retained, so the server is
248   * garbage collected when it is no longer used, but it can not be
249   * retrieved at a later date using {@link #findMBeanServer}.
250   * Calling this method is equivalent to calling
251   * {@link newMBeanServer(String)} with a <code>null</code> value.
252   *
253   * @return a new {@link MBeanServer} instance.
254   * @throws SecurityException if a security manager exists and the
255   *                           caller's permissions don't imply {@link
256   *                           MBeanServerPermission(String)}("newMBeanServer")
257   * @throws JMRuntimeException if the property
258   *                     <code>javax.management.builder.initial</code>
259   *                     exists but names a class which either can not be
260   *                     instantiated or provides an implementation that returns
261   *                     <code>null</code> from either
262   *                     {@link MBeanServerBuilder#newMBeanServerDelegate()}
263   *                     or {@link MBeanServerBuilder#newMBeanServer()}
264   * @throws ClassCastException if the property
265   *                     <code>javax.management.builder.initial</code>
266   *                     exists but names a class which is not a subclass
267   *                     of {@link MBeanServerBuilder}.
268   * @see #newMBeanServer(String)
269   */
270  public static MBeanServer newMBeanServer()
271  {
272    return newMBeanServer(null);
273  }
274
275  /**
276   * Returns a server implementation using the default domain name
277   * given, or <code>"DefaultDomain"</code> if this is <code>null</code>.
278   * The default domain name is used when the domain name specified by
279   * the user is <code>null</code.  No reference to the created server is
280   * retained, so the server is garbage collected when it is no longer
281   * used, but it can not be retrieved at a later date using
282   * {@link #findMBeanServer}.
283   *
284   * @param domain the default domain name of the server.
285   * @return a new {@link MBeanServer} instance.
286   * @throws SecurityException if a security manager exists and the
287   *                           caller's permissions don't imply {@link
288   *                           MBeanServerPermission(String)}("newMBeanServer")
289   * @throws JMRuntimeException if the property
290   *                     <code>javax.management.builder.initial</code>
291   *                     exists but names a class which either can not be
292   *                     instantiated or provides an implementation that returns
293   *                     <code>null</code> from either
294   *                     {@link MBeanServerBuilder#newMBeanServerDelegate()}
295   *                     or {@link MBeanServerBuilder#newMBeanServer()}
296   * @throws ClassCastException if the property
297   *                     <code>javax.management.builder.initial</code>
298   *                     exists but names a class which is not a subclass
299   *                     of {@link MBeanServerBuilder}.
300   */
301  public static MBeanServer newMBeanServer(String domain)
302  {
303    SecurityManager sm = System.getSecurityManager();
304    if (sm != null)
305      sm.checkPermission(new MBeanServerPermission("newMBeanServer"));
306    return createServer(domain);
307  }
308
309  /**
310   * Common method to create a server for the {@link #createMBeanServer(String)}
311   * and {@link #newMBeanServer(String)} methods above.
312   *
313   * @param domain the default domain name of the server.
314   * @throws JMRuntimeException if the property
315   *                     <code>javax.management.builder.initial</code>
316   *                     exists but names a class which either can not be
317   *                     instantiated or provides an implementation that returns
318   *                     <code>null</code> from either
319   *                     {@link MBeanServerBuilder#newMBeanServerDelegate()}
320   *                     or {@link MBeanServerBuilder#newMBeanServer()}
321   * @throws ClassCastException if the property
322   *                     <code>javax.management.builder.initial</code>
323   *                     exists but names a class which is not a subclass
324   *                     of {@link MBeanServerBuilder}.
325   */
326  private static MBeanServer createServer(String domain)
327    {
328    if (domain == null)
329      domain = "DefaultDomain";
330    String builderClass =
331      SystemProperties.getProperty("javax.management.builder.initial");
332    if (builderClass == null)
333      {
334        if (builder == null ||
335            builder.getClass() != MBeanServerBuilder.class)
336          builder = new MBeanServerBuilder();
337      }
338    else if (!(builder != null &&
339               builderClass.equals(builder.getClass().getName())))
340      {
341        ClassLoader cl = Thread.currentThread().getContextClassLoader();
342        if (cl == null)
343          cl = MBeanServerFactory.class.getClassLoader();
344        try
345          {
346            Class<?> bClass = Class.forName(builderClass, true, cl);
347            builder = (MBeanServerBuilder) bClass.newInstance();
348          }
349        catch (ClassNotFoundException e)
350          {
351            throw (JMRuntimeException) (new JMRuntimeException("The builder class, "
352                                                               + builderClass +
353                                                               ", could not be found."))
354              .initCause(e);
355          }
356        catch (InstantiationException e)
357          {
358            throw (JMRuntimeException) (new JMRuntimeException("The builder class, "
359                                                               + builderClass +
360                                                               ", could not be instantiated."))
361              .initCause(e);
362          }
363        catch (IllegalAccessException e)
364          {
365            throw (JMRuntimeException) (new JMRuntimeException("The builder class, "
366                                                               + builderClass +
367                                                               ", could not be accessed."))
368              .initCause(e);
369          }
370      }
371    MBeanServerDelegate delegate = builder.newMBeanServerDelegate();
372    if (delegate == null)
373      throw new JMRuntimeException("A delegate could not be created.");
374    MBeanServer server = builder.newMBeanServer(domain, null, delegate);
375    if (server == null)
376      throw new JMRuntimeException("A server could not be created.");
377    return server;
378  }
379
380  /**
381   * Removes the reference to the specified server, thus allowing it to
382   * be garbage collected.
383   *
384   * @param server the server to remove.
385   * @throws IllegalArgumentException if a reference to the server is not
386   *                                  held (i.e. it wasn't created by
387   *                                  {@link #createMBeanServer(String)}
388   *                                  or this method has already been called
389   *                                  on it.
390   * @throws SecurityException if a security manager exists and the
391   *                           caller's permissions don't imply {@link
392   *                           MBeanServerPermission(String)}("releaseMBeanServer")
393   */
394  public static void releaseMBeanServer(MBeanServer server)
395  {
396    SecurityManager sm = System.getSecurityManager();
397    if (sm != null)
398      sm.checkPermission(new MBeanServerPermission("releaseMBeanServer"));
399    Iterator<MBeanServer> i = servers.values().iterator();
400    while (i.hasNext())
401      {
402        MBeanServer s = i.next();
403        if (server == s)
404          {
405            i.remove();
406            return;
407          }
408      }
409    throw new IllegalArgumentException("The server given is not referenced.");
410  }
411
412
413}