Added a utility class/method to create proxies that implement

subinterfaces of InvocationProvider and forward requests to peer nodes 
in order to use the same methods on owning peers and cloning peers.


git-svn-id: svn+ssh://src.earth.threerings.net/narya/trunk@4546 542714f4-19e9-0310-aa3c-eee0fc999fb1

src/java/com/threerings/presents/peer/util/PeerUtil.java

@@ -0,0 +1,74 @@
+//
+// $Id: PeerClient.java 4509 2007-01-24 00:22:07Z dhoover $
+//
+// 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.peer.util;
+
+import java.util.HashMap;
+
+import java.lang.reflect.InvocationHandler;
+import java.lang.reflect.Method;
+import java.lang.reflect.Proxy;
+
+import com.threerings.presents.client.Client;
+import com.threerings.presents.client.InvocationService;
+import com.threerings.presents.server.InvocationProvider;
+
+/**
+ * Static methods of general utility for peer nodes.
+ */
+public class PeerUtil
+{
+    /**
+     * Creates a proxy object implementing the specified provider interface (a subinterface of
+     * {@link InvocationProvider} that forwards requests to the given service implementation
+     * (a subinterface of {@link InvocationService} corresponding to the provider interface)
+     * on the specified client.  This is useful for server entities that need to call a method
+     * either on the current server (with <code>null</code> as the caller parameter) or on a
+     * peer server.
+     *
+     * @param clazz the subclass of {@link InvocationProvider} desired to be implemented
+     * @param svc the implementation of the corresponding subclass of {@link InvocationService}
+     * @param client the client to pass to the service methods
+     */
+    public static <S extends InvocationProvider, T extends InvocationService>
+        S createProviderProxy (Class<S> clazz, final T svc, final Client client)
+    {
+        return clazz.cast(Proxy.newProxyInstance(
+            clazz.getClassLoader(), new Class[] { clazz },
+            new InvocationHandler() {
+                public Object invoke (Object proxy, Method method, Object[] args)
+                    throws Throwable {
+                    Method smethod = _pmethods.get(method);
+                    if (smethod == null) {
+                        Class[] ptypes = method.getParameterTypes();
+                        ptypes[0] = Client.class;
+                        _pmethods.put(method, smethod = svc.getClass().getMethod(
+                            method.getName(), ptypes));
+                    }
+                    args[0] = client;
+                    return smethod.invoke(svc, args);
+                }
+            }));
+    }
+
+    /** Maps provider interface methods to service interface methods. */
+    protected static HashMap<Method, Method> _pmethods = new HashMap<Method, Method>();
+}