Added some magic on the road toward more elegant support for dynamic languages

like Groovy and JRuby. Created a DynamicEventDispatcher that automatically maps
attribute, element and set events to methods. Say you have a field:

  public DSet occupantInfo;

you can create a method in any class:

  public void occupantInfoAdded (BodyObject source, OccupantInfo entry);

and then bind that class as a listener using the dynamic event dispatcher:

  _myobj.addListener(new DynamicEventDispatcher(object));

I also created a nicer replacement for the MessageHandler system which is
clunky but still way simpler than using a full InvocationService. Basically we
dispatch MessageEvent as if it were a method call. 

For example, in AtlantiManager I define:

    public void placeTile (BodyObject placer, AtlantiTile tile)

which receives a request by a player to place a tile on their turn. Then in
AtlantiController, I simply call:

   _atlobj.manager.invoke("placeTile", tile);

Of course, in JRuby and Groovy, that's going to look like:

   _atlobj.manager.placeTile(tile);

which is all part of the fun.


git-svn-id: svn+ssh://src.earth.threerings.net/narya/trunk@4344 542714f4-19e9-0310-aa3c-eee0fc999fb1

src/java/com/threerings/presents/dobj/DynamicEventDispatcher.java

@@ -0,0 +1,135 @@
+//
+// $Id$
+//
+// Narya library - tools for developing networked games
+// Copyright (C) 2002-2006 Three Rings Design, Inc., All Rights Reserved
+// http://www.threerings.net/code/narya/
+//
+// This library is free software; you can redistribute it and/or modify it
+// under the terms of the GNU Lesser General Public License as published
+// by the Free Software Foundation; either version 2.1 of the License, or
+// (at your option) any later version.
+//
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+// Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public
+// License along with this library; if not, write to the Free Software
+// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+
+package com.threerings.presents.dobj;
+
+import java.lang.reflect.Method;
+
+import java.util.HashMap;
+import java.util.logging.Level;
+
+import com.samskivert.util.MethodFinder;
+import com.samskivert.util.StringUtil;
+
+import static com.threerings.presents.Log.log;
+
+/**
+ * Maps distributed object events to methods using reflection.
+ */
+public class DynamicEventDispatcher
+    implements AttributeChangeListener, ElementUpdateListener, SetListener
+{
+    /**
+     * Creates a dynamic event dispatcher on the supplied target.
+     */
+    public DynamicEventDispatcher (Object target)
+    {
+        _target = target;
+        _finder = new MethodFinder(target.getClass());
+    }
+
+    // from interface AttributeChangeListener
+    public void attributeChanged (AttributeChangedEvent event)
+    {
+        dispatchMethod(event.getName() + "Changed",
+            new Object[] { event.getValue() });
+    }
+
+    // from interface ElementUpdateListener
+    public void elementUpdated (ElementUpdatedEvent event)
+    {
+        dispatchMethod(event.getName() + "Updated",
+            new Object[] { event.getIndex(), event.getValue() });
+    }
+
+    // from interface SetListener
+    public void entryAdded (EntryAddedEvent event)
+    {
+        dispatchMethod(event.getName() + "Added",
+            new Object[] { event.getEntry() });
+    }
+
+    // from interface SetListener
+    public void entryUpdated (EntryUpdatedEvent event)
+    {
+        dispatchMethod(event.getName() + "Updated",
+            new Object[] { event.getEntry() });
+    }
+
+    // from interface SetListener
+    public void entryRemoved (EntryRemovedEvent event)
+    {
+        dispatchMethod(event.getName() + "Removed",
+            new Object[] { event.getKey() });
+    }
+
+    /**
+     * Dynamically looks up the method in question on our target and dispatches
+     * an event if it does.
+     */
+    public void dispatchMethod (String name, Object[] arguments)
+    {
+        // first check the cache
+        Method method = _mcache.get(name);
+        if (method == null) {
+            // if we haven't already determined this method doesn't exist, try
+            // to resolve it
+            if (!_mcache.containsKey(name)) {
+                _mcache.put(name, method = resolveMethod(name, arguments));
+            }
+        }
+        if (method != null) {
+            try {
+                method.invoke(_target, arguments);
+            } catch (Exception e) {
+                log.log(Level.WARNING, "Failed to dispatch event callback " +
+                    name + "(" + StringUtil.toString(arguments) + ").", e);
+            }
+        }
+    }
+
+    /**
+     * Looks for a method that matches the supplied signature.
+     */
+    protected Method resolveMethod (String name, Object[] arguments)
+    {
+        Class clazz = _target.getClass();
+        Class[] ptypes = new Class[arguments.length];
+        for (int ii = 0; ii < arguments.length; ii++) {
+            ptypes[ii] = arguments[ii] == null ?
+                Object.class : arguments[ii].getClass();
+        }
+        try {
+            return _finder.findMethod(name, ptypes);
+        } catch (Exception e) {
+            return null;
+        }
+    }
+
+    /** The object on which we will dynamically dispatch events. */
+    protected Object _target;
+
+    /** Used to look up methods. */
+    protected MethodFinder _finder;
+
+    /** A cache of already resolved methods. */
+    protected HashMap<String,Method> _mcache = new HashMap<String,Method>();
+}