ParameterNoticeBoard
Class EventBroadcaster

java.lang.Object
  java.lang.Thread
      ParameterNoticeBoard.EventBroadcaster

All Implemented Interfaces:

java.lang.Runnable

 class EventBroadcaster
extends java.lang.Thread

Used to broadcast an event on a item in the parameter noticeboard to all of the listeners which have subscribed to it. It does this by creating thread for each listener in order to send the update to all of the listeners simultaneously. All of the threads are syncronised at the end of the run method. The advantage of this is that if one of the listeners has gone away and the ORB spends sometime working this out, the rest of the listeners will be updated asyncronously. If an attempt to connect to a listener fails, that listener is then removed from the list of listeners which are associated with that parameter noticeboard item.

The class makes extensive use of the new concurrency features of Java 5.0 and in particular it uses the ExecutorService in order to fire off the update listener threads and then again to syncronise when all of the threads have completed.

Version:

$Id: EventBroadcaster.java,v 1.3 2008/05/21 11:16:41 cb Exp $

Author:

Craige Bevil

Nested Class Summary

private class

EventBroadcaster.ListenerUpdaterThread This inner class will be used to update the listener within it's own thread by

Nested classes/interfaces inherited from class java.lang.Thread

java.lang.Thread.State, java.lang.Thread.UncaughtExceptionHandler

Field Summary

private java.util.concurrent.ExecutorService	ListenerUpdateThreadService This is used for starting threads which will be used to update listeners when there are events on the parameters which they are subscribed to
private java.util.concurrent.ConcurrentHashMap<java.lang.String,NonResponsiveClient>	NonResponsiveClientHash Used to keep a track of the non-responsive clients
(package private) java.util.concurrent.ConcurrentHashMap<iParameterNoticeBoard.ParameterNoticeBoardListener,ParameterSubscriber>	ParameterListeners This is a hash map which contains the listeners which are subscribed to this particular parameter.
(package private) java.lang.String	ParameterName This is the name of the parameter which has had the update.
(package private) org.omg.CORBA.Any	ParameterValue This is the value of the parameter which is to be broadcast
(package private) MessageHandler	SyslogMessageHandler Used for interacting with the syslog

Fields inherited from class java.lang.Thread

MAX_PRIORITY, MIN_PRIORITY, NORM_PRIORITY

Constructor Summary

EventBroadcaster(java.util.concurrent.ConcurrentHashMap<java.lang.String,NonResponsiveClient> NonResponsiveClientHash, java.util.concurrent.ConcurrentHashMap<iParameterNoticeBoard.ParameterNoticeBoardListener,ParameterSubscriber> ParameterListeners, java.lang.String ParameterName, org.omg.CORBA.Any ParameterValue, MessageHandler SyslogMessageHandler)
Constructor

Method Summary

void	run() The main method of the thread.

Methods inherited from class java.lang.Thread

activeCount, checkAccess, countStackFrames, currentThread, destroy, dumpStack, enumerate, getAllStackTraces, getContextClassLoader, getDefaultUncaughtExceptionHandler, getId, getName, getPriority, getStackTrace, getState, getThreadGroup, getUncaughtExceptionHandler, holdsLock, interrupt, interrupted, isAlive, isDaemon, isInterrupted, join, join, join, resume, setContextClassLoader, setDaemon, setDefaultUncaughtExceptionHandler, setName, setPriority, setUncaughtExceptionHandler, sleep, sleep, start, stop, stop, suspend, toString, yield

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

ListenerUpdateThreadService

private java.util.concurrent.ExecutorService ListenerUpdateThreadService

This is used for starting threads which will be used to update listeners when there are events on the parameters which they are subscribed to

NonResponsiveClientHash

private java.util.concurrent.ConcurrentHashMap<java.lang.String,NonResponsiveClient> NonResponsiveClientHash

Used to keep a track of the non-responsive clients

ParameterListeners

java.util.concurrent.ConcurrentHashMap<iParameterNoticeBoard.ParameterNoticeBoardListener,ParameterSubscriber> ParameterListeners

This is a hash map which contains the listeners which are subscribed to this particular parameter.

ParameterName

java.lang.String ParameterName

This is the name of the parameter which has had the update.

ParameterValue

org.omg.CORBA.Any ParameterValue

This is the value of the parameter which is to be broadcast

SyslogMessageHandler

MessageHandler SyslogMessageHandler

Used for interacting with the syslog

Constructor Detail

EventBroadcaster

EventBroadcaster(java.util.concurrent.ConcurrentHashMap<java.lang.String,NonResponsiveClient> NonResponsiveClientHash,
                 java.util.concurrent.ConcurrentHashMap<iParameterNoticeBoard.ParameterNoticeBoardListener,ParameterSubscriber> ParameterListeners,
                 java.lang.String ParameterName,
                 org.omg.CORBA.Any ParameterValue,
                 MessageHandler SyslogMessageHandler)

Constructor

Parameters:

NonResponsiveClientHash - This is a hash which contains a list of all of the clients which are not responsive.

ParameterListeners - This is a hash map of all of the listeners which are subscribed to this parameter noticeboard item.

ParameterName - This is the name of the item in the parameter noticeboard which these listeners are subscribed.

ParameterValue - This is the CORBA any value which contains the event which is to be redistributed.

SyslogMessageHandler - This is a object which can be used to interact with the syslog.

Method Detail

run

public void run()

The main method of the thread. Will spawn a thread for every listener which is subscribed to the parameter noticeboard and update that listener. It will then wait until all of them listener threads have completed before it itself will terminate.

Specified by:

run in interface java.lang.Runnable

Overrides:

run in class java.lang.Thread