I am currently trying the approach to Singleton MBeans for clustering suggested in the
JBoss Clustering article by Ivelin Ivanov at
http://www.onjava.com/pub/a/onjava/2003/08/20/jboss_clustering.html, however there is
not enough information in the article -- and I am still working on this approach. I
have modified a singleton class to be a singleton MBean as described but as yet I am
having trouble with the JBoss not being able to start the service, with complaints of
a nested throwable and an method not being available in the singleton class:
| 12:38:51,141 ERROR [URLDeploymentScanner] Incomplete Deployment listing:
| Incompletely deployed packages:
| [EMAIL PROTECTED] {
url=file:/C:/jboss-3.2.5/server/all/farm/cluster-examples-service.xml }
| deployer: [EMAIL PROTECTED]
| status: Deployment FAILED reason: create operation failed for package
file:/C:/jboss-3.2.5/server/all/farm/cluster-examples-service.xml; - nested throwable:
(org.jboss.deployment.DeploymentException:
com.harborsideplus.grover.mbean.AllUserMessagesSingleton.<init>(); - nested throwable:
(java.lang.NoSuchMethodException:
com.harborsideplus.grover.mbean.AllUserMessagesSingleton.<init>()))
| state: FAILED
| watch: file:/C:/jboss-3.2.5/server/all/farm/cluster-examples-service.xml
|
I have modified the singleton to be a MBean as described in the article, the MBean and
interfaces are listed below:
| // ---------- All UserMessagesSingletonMBean interface ----------------
| package com.harborsideplus.grover.mbean;
|
| import com.harborsideplus.grover.util.UserMessages;
|
| /**
| * @author James Adams
| *
| */
| public interface AllUserMessagesSingletonMBean
| {
|
//================================================================================
| // managed MBean operations, which control the lifecycle of the singleton
service
|
//================================================================================
| public void startSingleton ();
| public void stopSingleton ();
|
|
|
//================================================================================
| // exposed methods
|
//================================================================================
|
| /**
| *
| * @return
| */
| public boolean isMasterNode ();
|
|
| /**
| * Get the user's messages beginning at the specified index.
| *
| * @param userId
| * @param index
| * @return
| */
| public UserMessages getUserMessages (String userId,
| int index);
|
|
| /**
| * Add a message for the specified user. If the specified user doesn't already
| * have a UserMessages list then one will be initialized before adding the
message.
| *
| * @param userId
| * @param message
| */
| public void addMessage (String userId,
| String message);
|
|
| /**
| * Get the number of messages for the specified user.
| * @param userId
| * @return
| */
| public int getNumberOfUserMessages (String userId);
|
| }
|
|
|
| //----------- AllUserMessagesSingleton class ---------------------
|
| package com.harborsideplus.grover.mbean;
|
| import java.util.ArrayList;
| import java.util.Enumeration;
| import java.util.Hashtable;
|
| import com.harborsideplus.grover.util.UserMessages;
|
| /**
| * @author James Adams
| *
| */
| public class AllUserMessagesSingleton
| implements AllUserMessagesSingletonMBean
| {
| // reference to the singleton
| private static AllUserMessagesSingleton m_reference;
|
| // hashtable of UserMessages
| private Hashtable m_userMessagesTable;
|
| // flag showing whether or not running on master node
| private boolean m_isMasterNode;
|
|
|
//================================================================================
| // managed MBean operations, which control the lifecycle of the singleton
service
|
//================================================================================
|
| /**
| *
| */
| public void startSingleton ()
| {
| m_isMasterNode = true;
| }
|
| /**
| *
| */
| public void stopSingleton ()
| {
| m_isMasterNode = false;
| }
|
|
| //=============================================================
| // Singleton-related methods
| //=============================================================
|
| /**
| * Constructor method which is private to insure that the class can't be
instantiated.
| * A reference to an object of the class must be obtained via the
getIOIMessagesBean() method.
| *
| */
| private AllUserMessagesSingleton ()
| {
| // initialize the ArrayList
| m_userMessagesTable = new Hashtable();
| }
|
|
| /**
| * Method used to obtain a reference to the object.
| *
| * @return reference to the singleton object
| */
| public static synchronized AllUserMessagesSingleton getReference ()
| {
| // if the reference hasn't already been created then instantiate an object
| if (m_reference == null)
| {
| // call the constructor
| m_reference = new AllUserMessagesSingleton();
| }
|
| // return our reference
| return m_reference;
| }
|
|
| /**
| * Method provided in order to prevent cloning of the object. The method
always throws an
| * exception to indicate that cloning is not supported by this class.
| *
| * @return never returns anything
| * @throws CloneNotSupportedException to inicate that cloning is not supported
by this class
| */
| public Object clone ()
| throws CloneNotSupportedException
| {
| // do not allow cloning - throw an exception
| throw new CloneNotSupportedException();
| }
|
|
| //======================================================================
| // Public methods
| //======================================================================
|
| /**
| *
| */
| public boolean isMasterNode ()
| {
| return m_isMasterNode;
| }
|
|
| /**
| * Get the UserMessages for the specified user.
| *
| * @param userId
| * @return
| */
| /*
| public UserMessages getUserMessages (String userId)
| {
| // handle null keys
| if (userId == null)
| {
| return null;
| }
|
| // return the corresponding UserMessages, or null if it doesn't exist
| return (UserMessages) m_userMessagesTable.get(userId);
| }
| */
|
| /**
| * Get the UserMessages for the specified user, from the specified index to
the end.
| *
| * @param userId
| * @param index
| * @return
| */
| public UserMessages getUserMessages (String userId,
| int index)
| {
| // handle bad parameters
| if ((userId == null) || (index < 0))
| {
| return null;
| }
|
| // get the UserMessages for the specified user
| UserMessages userMessages = (UserMessages) m_userMessagesTable.get(userId);
|
| if (userMessages != null)
| {
| // if the index is past the range then return null
| if (index > userMessages.getLastIndex())
| {
| return null;
| }
| // if the index is zero then we want the entire thing -- no need to
get a subset
| else if (index == 0)
| {
| return userMessages;
| }
| // return a subset of the original messages
| else
| {
| // index is within range - copy the messages from the index
| // to the end into a new UserMessages object and return it
|
| // create the new UserMessages we'll return
| UserMessages newUserMessages = new UserMessages(userId);
|
| // loop over the original messages, copying them into the new
messages object
| for (int i = index; i <= userMessages.getLastIndex(); i++)
| {
| newUserMessages.addMessage(userMessages.getMessage(i));
| }
|
| // return the messages
| return newUserMessages;
| }
| }
| else
| {
| // no messages were found for the specified user
| return null;
| }
| }
|
|
| /**
| * Add a message for the specified user. If the specified user doesn't already
| * have a UserMessages list then one will be initialized before adding the
message.
| *
| * @param userId
| * @param message
| */
| public void addMessage (String userId,
| String message)
| {
| // either add to an existing list or create one first before adding to it
| if (m_userMessagesTable.containsKey(userId))
| {
| // get the existing UserMessages for this user
| UserMessages userMessages = (UserMessages)
m_userMessagesTable.get(userId);
|
| // add the message to the list
| userMessages.addMessage(message);
| }
| else
| {
| // create a UserMessages for this user
| UserMessages userMessages = new UserMessages(userId);
|
| // add the message to the list
| userMessages.addMessage(message);
|
| // add the user messages list to the hash
| m_userMessagesTable.put(userId, userMessages);
| }
| }
|
|
| /**
| * Get the number of messages for the specified user.
| * @param userId
| * @return
| */
| public int getNumberOfUserMessages (String userId)
| {
| if (m_userMessagesTable.containsKey(userId))
| {
| return ((UserMessages) m_userMessagesTable.get(userId)).size();
| }
| else
| {
| return 0;
| }
| }
|
| }
|
|
|
The MBean classes are being included with my application's EJB Jar file which is part
of the EAR file which is deployed in the JBOSS_HOME/server/all/deploy directory.
I have modified JBOSS_HOME/server/all/farm/cluster-examples-service.xml by adding the
following entry:
| <!-- ===================================================== -->
| <!-- This MBean is an example of a cluster Singleton -->
| <!-- ===================================================== -->
| <mbean code="com.harborsideplus.grover.mbean.AllUserMessagesSingleton"
| name="grover.mbean:service=AllUserMessagesSingleton">
| </mbean>
|
| <!-- ===================================================== -->
| <!-- | This is a singleton controller which works similarly to the -->
| <!-- | SchedulerProvider (when a MBean target is used) -->
| <!-- ===================================================== -->
| <mbean code="org.jboss.ha.singleton.HASingletonController"
| name="jboss:service=HASingletonController">
| <depends>jboss:service=DefaultPartition</depends>
| <depends>grover.mbean:service=AllUserMessagesSingleton</depends>
| <attribute
name="TargetName">grover.mbean:service=AllUserMessagesSingleton</attribute>
| <attribute name="TargetStartMethod">startSingleton</attribute>
| <attribute name="TargetStopMethod">stopSingleton</attribute>
| </mbean>
|
Any suggestions as to what I am doing wrong ? Thanks in advance for any ideas,
feedback, etc.
-James
View the original post :
http://www.jboss.org/index.html?module=bb&op=viewtopic&p=3843109#3843109
Reply to the post :
http://www.jboss.org/index.html?module=bb&op=posting&mode=reply&p=3843109
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