support sending back exported objects to the caller.

git-svn-id: https://hudson.dev.java.net/svn/hudson/trunk/hudson/main@6627 71c3de6d-444a-0410-be80-ed276b4c234a

remoting/src/main/java/hudson/remoting/Channel.java

@@ -10,7 +10,6 @@ import java.io.ObjectOutputStream;
 import java.io.OutputStream;
 import java.io.PrintWriter;
 import java.io.UnsupportedEncodingException;
-import java.lang.reflect.Proxy;
 import java.util.Collections;
 import java.util.Hashtable;
 import java.util.Map;
@@ -361,8 +360,7 @@ public class Channel implements VirtualChannel {
 
         // proxy will unexport this instance when it's GC-ed on the remote machine.
         final int id = export(instance);
-        return type.cast(Proxy.newProxyInstance( type.getClassLoader(), new Class[]{type},
-            new RemoteInvocationHandler(id,userProxy)));
+        return RemoteInvocationHandler.wrap(null,id,type,userProxy);
     }
 
     /*package*/ int export(Object instance) {

remoting/src/main/java/hudson/remoting/IReadResolve.java

+package hudson.remoting;
+
+import java.io.ObjectStreamException;
+
+/**
+ * Used internally in the remoting code to have the proxy object
+ * implement readResolve.
+ *
+ * @author Kohsuke Kawaguchi
+ */
+public interface IReadResolve {
+    Object readResolve() throws ObjectStreamException;
+}

remoting/src/main/java/hudson/remoting/RemoteInvocationHandler.java

@@ -3,6 +3,8 @@ package hudson.remoting;
 import java.io.IOException;
 import java.io.ObjectInputStream;
 import java.io.Serializable;
+import java.io.ObjectOutputStream;
+import java.io.ObjectStreamException;
 import java.lang.reflect.InvocationHandler;
 import java.lang.reflect.InvocationTargetException;
 import java.lang.reflect.Method;
@@ -35,6 +37,15 @@ final class RemoteInvocationHandler implements InvocationHandler, Serializable {
      */
     private final boolean userProxy;
 
+    /**
+     * If true, indicates that this proxy object is being sent back
+     * to where it came from. If false, indicate sthat this proxy
+     * is being sent to the remote peer.
+     *
+     * Only used in the serialized form of this class.
+     */
+    private boolean goingHome;
+
     RemoteInvocationHandler(int id, boolean userProxy) {
         this.oid = id;
         this.userProxy = userProxy;
@@ -53,7 +64,7 @@ final class RemoteInvocationHandler implements InvocationHandler, Serializable {
      * Wraps an OID to the typed wrapper.
      */
     public static <T> T wrap(Channel channel, int id, Class<T> type, boolean userProxy) {
-        return type.cast(Proxy.newProxyInstance( type.getClassLoader(), new Class[]{type},
+        return type.cast(Proxy.newProxyInstance( type.getClassLoader(), new Class[]{type,IReadResolve.class},
             new RemoteInvocationHandler(channel,id,userProxy)));
     }
 
@@ -88,6 +99,13 @@ final class RemoteInvocationHandler implements InvocationHandler, Serializable {
     }
 
     public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
+        if(method.getDeclaringClass()==IReadResolve.class) {
+            // readResolve on the proxy.
+            // if we are going back to where we came from, replace the proxy by the real object
+            if(goingHome)   return channel.getExportedObject(oid);
+            else            return proxy;
+        }
+
         if(channel==null)
             throw new IllegalStateException("proxy is not connected to a channel");
 
@@ -115,6 +133,11 @@ final class RemoteInvocationHandler implements InvocationHandler, Serializable {
         ois.defaultReadObject();
     }
 
+    private void writeObject(ObjectOutputStream oos) throws IOException {
+        goingHome = channel!=null;
+        oos.defaultWriteObject();
+    }
+
     /**
      * Two proxies are the same iff they represent the same remote object. 
      */

remoting/src/test/java/hudson/remoting/ChannelRunner.java

@@ -20,7 +20,7 @@ interface ChannelRunner {
 
     Class<? extends ChannelRunner>[] LIST = new Class[] {
         InProcess.class,
-        Fork.class
+        // Fork.class
     };
 
 

remoting/src/test/java/hudson/remoting/SimpleTest.java

@@ -56,6 +56,30 @@ public class SimpleTest extends RmiTestBase {
         }
     }
 
+    /**
+     * Makes sure that proxied object can be sent back to the origin and resolve correctly.
+     */
+    public void test3() throws Exception {
+        Foo c = new Foo() {};
+
+        Foo r = channel.call(new Echo<Foo>(channel.export(Foo.class,c)));
+        assertSame(c,r);
+    }
+
+    public static interface Foo {}
+
+    private static class Echo<T> implements Callable<T,RuntimeException> {
+        private final T t;
+
+        Echo(T t) {
+            this.t = t;
+        }
+
+        public T call() throws RuntimeException {
+            return t;
+        }
+    }
+
     public static Test suite() throws Exception {
         return buildSuite(SimpleTest.class);
     }