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1   /*
2    * Copyright 2001-2002,2004 The Apache Software Foundation.
3    * 
4    * Licensed under the Apache License, Version 2.0 (the "License");
5    * you may not use this file except in compliance with the License.
6    * You may obtain a copy of the License at
7    * 
8    *      http://www.apache.org/licenses/LICENSE-2.0
9    * 
10   * Unless required by applicable law or agreed to in writing, software
11   * distributed under the License is distributed on an "AS IS" BASIS,
12   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13   * See the License for the specific language governing permissions and
14   * limitations under the License.
15   */
16  
17  
18  package org.apache.commons.modeler;
19  
20  
21  import java.util.Enumeration;
22  import java.util.Hashtable;
23  
24  import javax.management.AttributeChangeNotification;
25  import javax.management.InstanceNotFoundException;
26  import javax.management.MBeanException;
27  import javax.management.MBeanServer;
28  import javax.management.MBeanServerNotification;
29  import javax.management.Notification;
30  import javax.management.NotificationBroadcaster;
31  import javax.management.NotificationListener;
32  import javax.management.ObjectName;
33  import javax.naming.Context;
34  
35  import org.apache.commons.logging.Log;
36  import org.apache.commons.logging.LogFactory;
37  
38  // EXPERIMENTAL. It may fit better in tomcat jndi impl.
39  
40  
41  /***
42   *
43   * Link between JNDI and JMX. JNDI can be used for persistence ( it is
44   * an API for storing hierarchical data and a perfect fit for that ), as
45   * well as an alternate view of the MBean registry.
46   *
47   * If this component is enabled, all MBeans will be registered in JNDI, and
48   * all attributes that are set via JMX can be stored in a DirContext.
49   *
50   * This acts as a "recorder" for creation of mbeans and attribute changes
51   * done via JMX.
52   *
53   * XXX How can we control ( filter ) which mbeans will be registere ? Or
54   * attributes ?
55   * XXX How can we get the beans and attributes loaded before jndijmx ?
56   *
57   * The intended use:
58   * - do whatever you want to start the application
59   * - load JndiJmx as an mbean
60   * - make changes via JMX. All changes are recorded
61   * - you can use JndiJmx to save the changes in a Jndi context.
62   * - you can use JndiJmx to load changes from a JndiContext and replay them.
63   *
64   * The main benefit is that only changed attributes are saved, and the Jndi
65   * layer can preserve most of the original structure of the config file. The
66   * alternative is to override the config files with config info extracted
67   * from the live objects - but it's very hard to save only what was actually
68   * changed and preserve structure and comments.
69   *
70   * @author Costin Manolache
71   */
72  public class JndiJmx extends BaseModelMBean implements NotificationListener {
73  
74  
75      private static Log log= LogFactory.getLog(JndiJmx.class);
76  
77      protected Context componentContext;
78      protected Context descriptorContext;
79      protected Context configContext;
80  
81      MBeanServer mserver;
82  
83      /***
84       * Protected constructor to require use of the factory create method.
85       */
86      public JndiJmx() throws MBeanException {
87          super(JndiJmx.class.getName());
88      }
89  
90  
91      /*** If a JNDI context is set, all components
92       * will be registered in the context.
93       *
94       * @param ctx
95       */
96      public void setComponentContext(Context ctx) {
97          this.componentContext= ctx;
98      }
99  
100     /*** JNDI context for component descriptors ( metadata ).
101      *
102      * @param ctx
103      */
104     public void setDescriptorContext(Context ctx) {
105         this.descriptorContext= ctx;
106     }
107 
108     /*** JNDI context where attributes will be stored for persistence
109      *
110      */
111     public void setConfigContext( Context ctx ) {
112         this.configContext= ctx;
113     }
114 
115     // --------------------  Registration/unregistration --------------------
116     // temp - will only set in the jndi contexts
117     Hashtable attributes=new Hashtable();
118     Hashtable instances=new Hashtable();
119 
120     public void handleNotification(Notification notification, Object handback)
121     {
122         // register/unregister mbeans in jndi
123         if( notification instanceof MBeanServerNotification ) {
124             MBeanServerNotification msnot=(MBeanServerNotification)notification;
125 
126             ObjectName oname=msnot.getMBeanName();
127 
128             if( "jmx.mbean.created".equalsIgnoreCase( notification.getType() )) {
129                 try {
130                     Object mbean=mserver.getObjectInstance(oname);
131 
132                     if( log.isDebugEnabled() )
133                         log.debug( "MBean created " + oname + " " + mbean);
134 
135                     // XXX add filter support
136                     if( mbean instanceof NotificationBroadcaster ) {
137                         // register for attribute changes
138                         NotificationBroadcaster nb=(NotificationBroadcaster)mbean;
139                         nb.addNotificationListener(this, null, null);
140                         if( log.isDebugEnabled() )
141                             log.debug( "Add attribute change listener");
142                     }
143 
144                     instances.put( oname.toString(), mbean );
145                 } catch( InstanceNotFoundException ex ) {
146                     log.error( "Instance not found for the created object", ex );
147                 }
148             }
149             if( "jmx.mbean.deleted".equalsIgnoreCase( notification.getType() )) {
150                 instances.remove(oname.toString());
151             }
152         }
153 
154         // set attributes in jndi
155        //     if( "jmx.attribute.changed".equals( notification.getType() )) {
156         if( notification instanceof AttributeChangeNotification) {
157 
158             AttributeChangeNotification anotif=(AttributeChangeNotification)notification;
159             String name=anotif.getAttributeName();
160             Object value=anotif.getNewValue();
161             Object source=anotif.getSource();
162             String mname=null;
163 
164             Hashtable mbeanAtt=(Hashtable)attributes.get( source );
165             if( mbeanAtt==null ) {
166                 mbeanAtt=new Hashtable();
167                 attributes.put( source, mbeanAtt);
168                 if( log.isDebugEnabled())
169                     log.debug("First attribute for " + source );
170             }
171             mbeanAtt.put( name, anotif );
172 
173             log.debug( "Attribute change notification " + name + " " + value + " " + source );
174 
175         }
176 
177     }
178 
179     public String dumpStatus() throws Exception
180     {
181         StringBuffer sb=new StringBuffer();
182         Enumeration en=instances.keys();
183         while (en.hasMoreElements()) {
184             String on = (String) en.nextElement();
185             Object mbean=instances.get(on);
186             Hashtable mbeanAtt=(Hashtable)attributes.get(mbean);
187 
188             sb.append( "<mbean class=\"").append(on).append("\">");
189             sb.append( "\n");
190             Enumeration attEn=mbeanAtt.keys();
191             while (attEn.hasMoreElements()) {
192                 String an = (String) attEn.nextElement();
193                 AttributeChangeNotification anotif=
194                         (AttributeChangeNotification)mbeanAtt.get(an);
195                 sb.append("  <attribute name=\"").append(an).append("\" ");
196                 sb.append("value=\"").append(anotif.getNewValue()).append("\">");
197                 sb.append( "\n");
198             }
199 
200 
201             sb.append( "</mbean>");
202             sb.append( "\n");
203         }
204         return sb.toString();
205     }
206 
207     public void replay() throws Exception
208     {
209 
210 
211     }
212 
213 
214     public void init() throws Exception
215     {
216 
217         MBeanServer mserver=(MBeanServer)Registry.getRegistry().getMBeanServer();
218         ObjectName delegate=new ObjectName("JMImplementation:type=MBeanServerDelegate");
219 
220         // XXX need to extract info about previously loaded beans
221 
222         // we'll know of all registered beans
223         mserver.addNotificationListener(delegate, this, null, null );
224 
225     }
226 
227 }