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From akaras...@apache.org
Subject svn commit: rev 47040 - incubator/directory/seda/trunk/src/java/org/apache/seda/event
Date Wed, 22 Sep 2004 09:39:34 GMT
Author: akarasulu
Date: Wed Sep 22 02:39:32 2004
New Revision: 47040

Added:
   incubator/directory/seda/trunk/src/java/org/apache/seda/event/RoutingAdvice.java
Modified:
   incubator/directory/seda/trunk/src/java/org/apache/seda/event/DefaultEventRouter.java
   incubator/directory/seda/trunk/src/java/org/apache/seda/event/EventRouter.java
Log:
Commit changes ...

 o added RoutingAdvice interface
 o added method to apply advice to routing
 o added 1/2 implementation to publish
 
Todos ...

 o figure out what effective advice when is more than one advice is applicable
 o add changes for multiple applicaple advice to publish()
 o write some unit test cases to make sure this thing works and complies with
   the specified semantics.
   


Modified: incubator/directory/seda/trunk/src/java/org/apache/seda/event/DefaultEventRouter.java
==============================================================================
--- incubator/directory/seda/trunk/src/java/org/apache/seda/event/DefaultEventRouter.java
(original)
+++ incubator/directory/seda/trunk/src/java/org/apache/seda/event/DefaultEventRouter.java
Wed Sep 22 02:39:32 2004
@@ -17,9 +17,9 @@
 package org.apache.seda.event;
 
 
-import java.util.Set;
-import java.util.HashSet;
+import java.util.List;
 import java.util.Iterator;
+import java.util.ArrayList;
 import java.util.EventObject;
 
 
@@ -31,8 +31,10 @@
  */
 public class DefaultEventRouter implements EventRouter
 {
-    /** the set of subscriptions made with this router */
-    private Set subscriptions = new HashSet();
+    /** a list of applied routing advice */
+    private List adviceList = new ArrayList( 2 );
+    /** the list of subscriptions made with this router */
+    private List subscriptions = new ArrayList( 15 );
     /** the monitor - initially set to the null monitor */
     private EventRouterMonitor monitor = new EventRouterMonitorAdapter();
     
@@ -152,36 +154,108 @@
      */
     public void publish( EventObject event ) 
     {
-        final Subscription [] l_subscriptions;
-        
+        final ArrayList applicableAdvice = new ArrayList();
+
+        // --------------------------------------------------------------------
+        // Try and see what advice we can apply
+        // --------------------------------------------------------------------
+
+        synchronized( adviceList )
+        {
+            for ( int ii = 0; ii < adviceList.size(); ii++ )
+            {
+                RoutingAdvice advice = ( RoutingAdvice ) adviceList.get( ii ) ;
+
+                if ( advice.isApplicable( event ) )
+                {
+                    applicableAdvice.add( advice );
+                }
+            }
+        }
+
+
+        Subscription[] subscrArray;
         synchronized ( subscriptions )
         {
-            l_subscriptions = ( Subscription [] ) subscriptions
+            subscrArray = ( Subscription [] ) subscriptions
                 .toArray( new Subscription [ subscriptions.size() ] );
         }
 
-        for ( int ii = 0; ii < l_subscriptions.length; ii++ )
+        if ( applicableAdvice.isEmpty() )
         {
-            boolean isAssignable = l_subscriptions[ii].getType()
-                .isAssignableFrom( event.getClass() );
-            
+
+            publish( event, subscrArray );
+            return;
+        }
+
+
+        if ( applicableAdvice.size() == 1 )
+        {
+            RoutingAdvice advice = ( RoutingAdvice ) adviceList.get( 0 ) ;
+            publish( advice.getEvent( event ),
+                advice.getSubscriptions( event, subscrArray ) );
+            return;
+        }
+
+        throw new UnsupportedOperationException( "only one advice supported" );
+
+        /*
+         * you know I'm still not sure what sematics are best here whether to
+         * keep resubsituting events and the subscriptions or what.
+         *
+
+        EventObject newEvent = null;
+        for ( int ii = 0; ii < applicableAdvice.size(); ii++ )
+        {
+            RoutingAdvice advice = ( RoutingAdvice ) adviceList.get( ii ) ;
+
+            if ( ii >= applicableAdvice.size() - 1 )
+            {
+                newEvent = advice.getEvent( event );
+
+            }
+        }
+        */
+
+    }
+
+
+
+    private void publish( EventObject ev, Subscription[] subscriptions )
+    {
+        for ( int ii = 0; ii < subscriptions.length; ii++ )
+        {
+            boolean isAssignable = subscriptions[ii].getType()
+                .isAssignableFrom( ev.getClass() );
+
             if ( ! isAssignable )
             {
                 continue;
             }
-            
-            if ( l_subscriptions[ii].getFilter() == null )
+
+            if ( subscriptions[ii].getFilter() == null )
             {
-                l_subscriptions[ii].getSubscriber().inform( event );
+                subscriptions[ii].getSubscriber().inform( ev );
             }
-            else if ( l_subscriptions[ii].getFilter().accept( event ) )  
+            else if ( subscriptions[ii].getFilter().accept( ev ) )
             {
-                l_subscriptions[ii].getSubscriber().inform( event );
+                subscriptions[ii].getSubscriber().inform( ev );
             }
         }
     }
-    
-    
+
+
+    /**
+     * Adds advice to the advice list.
+     *
+     * @param advice the advice to apply
+     */
+    public void apply( RoutingAdvice advice )
+    {
+        adviceList.add( advice );
+    }
+
+
     /**
      * Sets the event router's monitor.
      * 

Modified: incubator/directory/seda/trunk/src/java/org/apache/seda/event/EventRouter.java
==============================================================================
--- incubator/directory/seda/trunk/src/java/org/apache/seda/event/EventRouter.java	(original)
+++ incubator/directory/seda/trunk/src/java/org/apache/seda/event/EventRouter.java	Wed Sep
22 02:39:32 2004
@@ -41,7 +41,7 @@
     /**
      * Subscribes an event subscriber.
      * 
-     * @param type an event type enumeration value
+     * @param type an event type
      * @param subscriber the Subscriber to subscribe
      */
     void subscribe( Class type, Subscriber subscriber );
@@ -56,6 +56,7 @@
     /**
      * Unsubscribes an event subscriber.
      * 
+     * @param type an event type
      * @param subscriber the Subscriber to unsubscribe
      */
     void unsubscribe( Class type, Subscriber subscriber );
@@ -67,4 +68,11 @@
      * @param event the event to publish
      */
     void publish( EventObject event );
+
+    /**
+     * Applies some routing advice to applicable events.
+     *
+     * @param advice the advice to apply
+     */
+    void apply( RoutingAdvice advice );
 }

Added: incubator/directory/seda/trunk/src/java/org/apache/seda/event/RoutingAdvice.java
==============================================================================
--- (empty file)
+++ incubator/directory/seda/trunk/src/java/org/apache/seda/event/RoutingAdvice.java	Wed Sep
22 02:39:32 2004
@@ -0,0 +1,66 @@
+/*
+ *   Copyright 2004 The Apache Software Foundation
+ *
+ *   Licensed under the Apache License, Version 2.0 (the "License");
+ *   you may not use this file except in compliance with the License.
+ *   You may obtain a copy of the License at
+ *
+ *       http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *   Unless required by applicable law or agreed to in writing, software
+ *   distributed under the License is distributed on an "AS IS" BASIS,
+ *   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *   See the License for the specific language governing permissions and
+ *   limitations under the License.
+ *
+ */
+package org.apache.seda.event;
+
+
+import java.util.EventObject;
+
+
+/**
+ * Used to add another dimension to making fine grained routing decisions.
+ * RoutingAdvice can add to or prune from the registered set of Subscriptions.
+ * They can transform the event by cloning before Subscribers are informed.
+ * Other types of logic using these substitutions can be used to implement a
+ * gambit of routing rules and behavoirs.  These objects are stackable in that
+ * more than one piece of advice can be used to route the same event: this is
+ * acheived by feeding the result of one advice operation into the input of
+ * another in a chain.
+ *
+ * @author <a href="mailto:directory-dev@incubator.apache.org">Apache Directory Project</a>
+ * @version $Rev$
+ */
+public interface RoutingAdvice
+{
+    /**
+     * Returns an alternative list of Subscriptions which may or may not be
+     * the same as those already registered with the router service.
+     *
+     * @param ev the original event without any chained substitutions
+     * @param subscriptions the subscriptions already registered with the router
+     * @return the advised list of subscriptions to use instead
+     */
+    public Subscription[] getSubscriptions( EventObject ev, Subscription[] subscriptions
);
+
+
+    /**
+     * Gets an alternative event to use as the argument to inform Subscribers
+     * which may or may not be the same as the event argument.
+     *
+     * @param ev the event being published
+     * @return the advised event to use instead
+     */
+    public EventObject getEvent( EventObject ev );
+
+
+    /**
+     * Checks to see if this advice is applicable to an event.
+     *
+     * @param ev the event to check for advice applicability
+     * @return true if this advice applies, false otherwise
+     */
+    public boolean isApplicable( EventObject ev );
+}

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