hammant 2002/11/29 13:30:07
Added: src/java/org/apache/avalon/cornerstone/blocks/event
DefaultEventManager.java
InvalidEventTypeException.java
src/java/org/apache/avalon/cornerstone/services/event
Event.java EventManager.java Filter.java
Publisher.java Register.java Subscriber.java
Log:
Mauro Talevi suppies "Event Notifier pattern by Gupta et al. (Java Report, Vol. 3,
No. 7, July 1998, 19-36)" block.
Revision Changes Path
1.1
jakarta-avalon-cornerstone/src/java/org/apache/avalon/cornerstone/blocks/event/DefaultEventManager.java
Index: DefaultEventManager.java
===================================================================
/*
* Copyright (C) The Apache Software Foundation. All rights reserved.
*
* This software is published under the terms of the Apache Software License
* version 1.1, a copy of which has been included with this distribution in
* the LICENSE.txt file.
*/
package org.apache.avalon.cornerstone.blocks.event;
import java.util.Hashtable;
import java.util.Enumeration;
import org.apache.avalon.framework.logger.AbstractLogEnabled;
import org.apache.avalon.framework.context.Contextualizable;
import org.apache.avalon.framework.context.Context;
import org.apache.avalon.framework.context.ContextException;
import org.apache.avalon.framework.configuration.Configurable;
import org.apache.avalon.framework.configuration.Configuration;
import org.apache.avalon.framework.configuration.ConfigurationException;
import org.apache.avalon.framework.service.Serviceable;
import org.apache.avalon.framework.service.ServiceManager;
import org.apache.avalon.framework.service.ServiceException;
import org.apache.avalon.framework.activity.Initializable;
import org.apache.avalon.framework.activity.Disposable;
import org.apache.avalon.phoenix.BlockContext;
import org.apache.avalon.cornerstone.services.event.Event;
import org.apache.avalon.cornerstone.services.event.Filter;
import org.apache.avalon.cornerstone.services.event.EventManager;
import org.apache.avalon.cornerstone.services.event.Publisher;
import org.apache.avalon.cornerstone.services.event.Register;
import org.apache.avalon.cornerstone.services.event.Subscriber;
/**
* EventManager Block
*
* @phoenix:block
* @phoenix:service name="org.apache.avalon.cornerstone.services.event.EventManager"
*
* @author Mauro Talevi
*/
public class DefaultEventManager extends AbstractLogEnabled
implements EventManager,
Contextualizable, Configurable, Serviceable, Initializable, Disposable
{
private final String m_rootEventType = "Event";
private Class m_eventClass;
private Publisher m_publisher = new DefaultPublisher();
private Register m_register = new DefaultRegister();
private Hashtable m_subscribers = new Hashtable();
public Publisher getPublisher(){
return m_publisher;
}
public Register getRegister(){
return m_register;
}
public void contextualize( final Context context )
{
}
public void configure( final Configuration configuration )
throws ConfigurationException
{
}
/**
* ServiceManager dependencies
*/
public void service( final ServiceManager serviceManager )
throws ServiceException
{
}
public void initialize()
throws Exception
{
m_eventClass = Class.forName( m_rootEventType );
getLogger().info("Initialising eventClass " + m_eventClass);
}
public void dispose()
{
}
class DefaultPublisher implements Publisher
{
public void publish( final Event event )
{
getLogger().info("Publishing event " + event.getClass());
System.out.println("Publishing event " + event.getClass());
for ( Enumeration e = m_subscribers.elements(); e.hasMoreElements(); ){
Subscriber subscriber = (Subscriber)e.nextElement();
if (subscriber.getEventType().isAssignableFrom(event.getClass())
&& (subscriber.getFilter() != null ||
subscriber.getFilter().filter(event))){
getLogger().info("Informing subscriber "+subscriber+" of event
"+event.getClass());
subscriber.inform(event);
}
}
}
}
class DefaultRegister implements Register
{
public void subscribe( final Subscriber subscriber )
throws InvalidEventTypeException
{
if ( !m_eventClass.isAssignableFrom( subscriber.getEventType() ) )
throw new InvalidEventTypeException();
getLogger().info( "Subscribing event " +
subscriber.getEventType().getName() );
// Add to list but prevent duplicate subscriptions
if ( !m_subscribers.containsKey( subscriber.getUID() ) ){
m_subscribers.put( subscriber.getUID(), subscriber );
getLogger().info( "Subscribed Event " +
subscriber.getEventType().getName() );
if ( getLogger().isDebugEnabled() ){
getLogger().debug( "Subscribers now active: " +
m_subscribers.size() );
}
}
}
public void unsubscribe( Subscriber subscriber )
throws InvalidEventTypeException
{
if ( !m_eventClass.isAssignableFrom( subscriber.getEventType() ) )
throw new InvalidEventTypeException();
if ( m_subscribers.containsKey( subscriber.getUID() ) ){
m_subscribers.remove( subscriber.getUID() );
getLogger().info( "Unsubscribed Event " +
subscriber.getEventType().getName() );
if ( getLogger().isDebugEnabled() ){
getLogger().debug( "Subscribers now active: " +
m_subscribers.size() );
}
} else {
getLogger().warn( "Subscriber " + subscriber.getUID() + " not found"
);
}
}
}
}
1.1
jakarta-avalon-cornerstone/src/java/org/apache/avalon/cornerstone/blocks/event/InvalidEventTypeException.java
Index: InvalidEventTypeException.java
===================================================================
/*
* Copyright (C) The Apache Software Foundation. All rights reserved.
*
* This software is published under the terms of the Apache Software License
* version 1.1, a copy of which has been included with this distribution in
* the LICENSE.txt file.
*/
package org.apache.avalon.cornerstone.blocks.event;
/**
* InvalidEventTypeException is thrown whenever the event type of a
<tt>Subscriber</tt>
* is not assignable from the root event type.
*
* @author Mauro Talevi
*/
public class InvalidEventTypeException extends RuntimeException
{
}
1.1
jakarta-avalon-cornerstone/src/java/org/apache/avalon/cornerstone/services/event/Event.java
Index: Event.java
===================================================================
/*
* Copyright (C) The Apache Software Foundation. All rights reserved.
*
* This software is published under the terms of the Apache Software License
* version 1.1, a copy of which has been included with this distribution in
* the LICENSE.txt file.
*/
package org.apache.avalon.cornerstone.services.event;
import java.io.Serializable;
/**
* <tt>Event</tt> is a common ancestor type for all events.
*
* It is Serializable to allow events to be published and received
* in a distributed architecture.
*
* @author Mauro Talevi
*/
public interface Event extends Serializable
{
/**
* Returns the event type
* @return int representing the event type
*/
public int getType();
/**
* Returns the event source
* @return Object representing the event source
*/
public Object getSource();
}
1.1
jakarta-avalon-cornerstone/src/java/org/apache/avalon/cornerstone/services/event/EventManager.java
Index: EventManager.java
===================================================================
/*
* Copyright (C) The Apache Software Foundation. All rights reserved.
*
* This software is published under the terms of the Apache Software License
* version 1.1, a copy of which has been included with this distribution in
* the LICENSE.txt file.
*/
package org.apache.avalon.cornerstone.services.event;
/**
* <p>Service to manage event notification. The designed has been inspired by the
paper by
* Gupta, S., J. M. Hartkopf, and S. Ramaswamy, in Java Report, Vol. 3, No. 7, July
1998, 19-36,
* "Event Notifier: A Pattern for Event Notification".</p>
*
* <p>EventManager brokers events between a <tt>Publisher</tt>, which produces
events,
* and a <tt>Subscriber</tt>, which handles the notification of events.
* A <tt>Filter</tt> discards events not of interest to a subscriber.
* All Events have a common ancestor type <tt>Event</tt> and the event types are
* identified by a <tt>Class</tt>.</p>
*
* @author Mauro Talevi
*/
public interface EventManager
{
/**
* Represents Role of the service
*/
String ROLE = EventManager.class.getName();
/**
* Returns the Publisher with which events can be published.
*/
public Publisher getPublisher();
/**
* Returns the Register with which subscribers can
* subscribe and unsubscribe interest to given Events.
*/
public Register getRegister();
}
1.1
jakarta-avalon-cornerstone/src/java/org/apache/avalon/cornerstone/services/event/Filter.java
Index: Filter.java
===================================================================
/*
* Copyright (C) The Apache Software Foundation. All rights reserved.
*
* This software is published under the terms of the Apache Software License
* version 1.1, a copy of which has been included with this distribution in
* the LICENSE.txt file.
*/
package org.apache.avalon.cornerstone.services.event;
import java.io.Serializable;
/**
* A Filter allows subscribers to specify which events
* they should be informed of.
* It is Serializable to allow events to be published and received
* in a distributed architecture.
*
* @author Mauro Talevi
*/
public interface Filter extends Serializable
{
/**
* Filters event, discarding those not of interest to the subscriber.
*
* @param event the <tt>Event</tt>
* @return boolean <code>true</code> if Event passes filter
*/
public boolean filter( Event event );
}
1.1
jakarta-avalon-cornerstone/src/java/org/apache/avalon/cornerstone/services/event/Publisher.java
Index: Publisher.java
===================================================================
/*
* Copyright (C) The Apache Software Foundation. All rights reserved.
*
* This software is published under the terms of the Apache Software License
* version 1.1, a copy of which has been included with this distribution in
* the LICENSE.txt file.
*/
package org.apache.avalon.cornerstone.services.event;
/**
* <tt>Publisher</tt> produces or publishes events that are brokered by
<tt>EventManager</tt>
* and of which the appropriate subscribers are informed of.
*
* @author Mauro Talevi
*/
public interface Publisher
{
/**
* Publishes an event for subscribers to be informed of.
*
* @param event the <tt>Event</tt> being published
*/
public void publish( Event event );
}
1.1
jakarta-avalon-cornerstone/src/java/org/apache/avalon/cornerstone/services/event/Register.java
Index: Register.java
===================================================================
/*
* Copyright (C) The Apache Software Foundation. All rights reserved.
*
* This software is published under the terms of the Apache Software License
* version 1.1, a copy of which has been included with this distribution in
* the LICENSE.txt file.
*/
package org.apache.avalon.cornerstone.services.event;
/**
* <tt>Register</tt> allows a <tt>Subscriber</tt> to subscribe to
* and unsubscribe from <tt>EventManager</tt>.
*
* @author Mauro Talevi
*/
public interface Register
{
/**
* Subscribes a Subscriber to the EventManager.
* The Subscriber abstracts all the information needed for the subscription.
* @param subscriber the Subscriber
* @see Subscriber
*/
public void subscribe( Subscriber subscriber );
/**
* Unsubscribes an Subscriber from the EventManager.
* @param subscriber the Subscriber
* @see Subscriber
*/
public void unsubscribe( Subscriber subscriber );
}
1.1
jakarta-avalon-cornerstone/src/java/org/apache/avalon/cornerstone/services/event/Subscriber.java
Index: Subscriber.java
===================================================================
/*
* Copyright (C) The Apache Software Foundation. All rights reserved.
*
* This software is published under the terms of the Apache Software License
* version 1.1, a copy of which has been included with this distribution in
* the LICENSE.txt file.
*/
package org.apache.avalon.cornerstone.services.event;
/**
* <tt>Subscriber</tt> registers its interest in a class of events and
* filters the events of which it should be notified.
*
* @author Mauro Talevi
*/
public interface Subscriber
{
/**
* Returns UID (Unique ID) set when the subscriber is created.
* The UID is required when the subscriber is remote, since the
* <tt>Filter</tt> will in general be deep-copied to a new object.
*
* @return the String encoding the UID
*/
public String getUID();
/**
* Returns the event type of the event on which the Subscriber is interested.
* The event type is encoded by a <tt>Class</tt>.
*
* @return the <tt>Class</tt> encoding the event type
*/
public Class getEventType();
/**
* Returns the filter used to select the events in which the subscriber is
* interested.
*
* @return the <tt>Filter</tt>
*/
public Filter getFilter();
/**
* Callback method informing the Subscriber of the occurence of an event.
*
* @param event the <tt>Event</tt> of which the <tt>Subscriber</tt> is informed
*/
public void inform( Event event );
}
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