Writing a custom RMI Activator process

Question

Hello Group,
I am in the process of implementing a custom RMI activation scheme, in which remote Activatable objects will be hosted in a custom EXE process, instead of the standard Java.exe/Javaw.exe. I intend to use JNI to create the JVM in this custom EXE process and then load Java classes. I have used JNI to create JVMs in native processes before, but have no experience writing custom RMI activation systems.
Has anyone attempted this before, and knows if there are any gotchas that I should know early on?
Thanks,
Ranjit

Answer 1

I have a breakthrough. I am able to host a simple RMI server inside a custom EXE. All I do is inside the main of a Win32 EXE, create the JVM and use JNI to call the ‘main’ of a Java class I wrote below.
This class runs (some undocumented) code to bootstrap the RMI machinery. Hereafter my EXE process process remains alive and is available to service RMI requests. Using this approach, I wouldn’t need to recompile java.c inorder to rename it as long as my custom JNI code is able to parse in all the VM options passed in by RMID in order to create the JVM.
I was missing the crucial step of calling back into rmid (the Activator) and registering the newly created group, only after which would rmid start creating instances of the remote object. Your advice that I carefully read the spec helped!
public class Host {
public static void main(String[] args) throws Exception {
Class clsInputStream = Class.forName("sun.rmi.server.MarshalInputStream");
Constructor ctor = clsInputStream.getConstructor(InputStream.class);
Method readObj = clsInputStream.getMethod("readObject", null);
Method readLong = clsInputStream.getMethod("readLong", null);
// Instantiate MarshalInputStream
Object in = ctor.newInstance(System.in);
// Read all the data passed in by the Activator (rmid)
ActivationGroupID id = (ActivationGroupID) readObj.invoke(in);
ActivationGroupDesc desc = (ActivationGroupDesc) readObj.invoke(in);
long incarnation = (Long) readLong.invoke(in);
// Create the ActivationGroup
ActivationGroup grp = ActivationGroup.createGroup(id, desc, incarnation);
// Callback into rmid to register the group.
ActivationGroup.getSystem().activeGroup(id, grp, incarnation);
// rmid will now invoke ActivationGroup.newInstance to create the RMI server
Thanks,
Ranjit