Obtaining an IOR for RMI-IIOP

Question

Hi -
I'm working to modify a C program (gnuplot) so that it can remotely call functions in Java.
My current plan is to use RMI-IIOP on the Java side. I'd like to create a class that implements java.rmi.Remote via some local implementation class, instantiate it, then obtain a stringified IOR for that object and pass it to gnuplot, which can then use the IOR to call remote methods.
Also, I'm planning to use CORBA DII on the client side, since I want a generic program where the remote method names can be set by user options at run time.
Does this make sense? I'm working with this tutorial code:
http://java.sun.com/j2se/1.5.0/docs/guide/rmi-iiop/tutorial.html
and am stuck on obtaining an IOR in the server code.
Any help would be appreciated...

Answer 1

Well, I figured it out. The key method is remoteToCorba in com.sun.jndi.toolkit.corba.CorbaUtils. Here's my server code:
//HelloServer.java
import java.io.*;
import org.omg.CORBA.ORB;
import com.sun.jndi.toolkit.corba.CorbaUtils;
public class HelloServer {
    public static void main(String[] args) {
        try {
            // Step 1: Instantiate the Hello servant
            HelloImpl helloRef = new HelloImpl();
            // Step 2: Initialize the ORB
            ORB orb = ORB.init(args, null);
            // Step 3: Convert the Hello servant to a CORBA object
            org.omg.CORBA.Object corba_obj;
            corba_obj = CorbaUtils.remoteToCorba(helloRef, orb);
            // Step 4a: Announce the IOR to STDOUT
            String ior = orb.object_to_string(corba_obj);
            System.out.println("IOR: " + ior);
            // Step 4b: Announce the IOR to a file
            FileWriter fw = new FileWriter("hello.ior");
            fw.write(ior);
            fw.close();
            System.out.println("Hello Server: Ready...");
         } catch (Exception e) {
            System.out.println("Trouble: " + e);
            e.printStackTrace();
}And here's the matching client code:
//HelloClient.java
import java.io.*;
import org.omg.CORBA.ORB;
import javax.rmi.PortableRemoteObject;
public class HelloClient {
    public static void  main( String args[] ) {
        HelloInterface hi;
        try {
            // Step 1: Initialize the ORB
            ORB orb = ORB.init(args, null);
            // Step 2: Obtain the stringified IOR from a file
            FileReader fr = new FileReader("hello.ior");
            BufferedReader br = new BufferedReader(fr);
            String ior = br.readLine();
            // Step 3: Convert the IOR to a CORBA object reference
            org.omg.CORBA.Object objref = orb.string_to_object(ior);
            // Step 4: Narrow the CORBA object reference to the concrete type
            hi = (HelloInterface) PortableRemoteObject.narrow(
                objref, HelloInterface.class);
            // Step 5: Invoke the method.
            hi.sayHello( " MARS " );
        } catch( Exception e ) {
            System.err.println( "Exception " + e + "Caught" );
            e.printStackTrace( );
            return;
}The other two files are unchanged from the original example:
//HelloInterface.java
import java.rmi.Remote;
public interface HelloInterface extends java.rmi.Remote {
   public void sayHello( String from ) throws java.rmi.RemoteException;
//HelloImpl.java
import javax.rmi.PortableRemoteObject;
public class HelloImpl extends PortableRemoteObject implements HelloInterface {
   public HelloImpl() throws java.rmi.RemoteException {
       super();     // invoke rmi linking and remote object initialization
   public void sayHello( String from ) throws java.rmi.RemoteException {
       System.out.println( "Hello from " + from + "!!" );
       System.out.flush();
}Compilation and usage is straightforward:
javac *.java
rmic -iiop HelloImpl
java -cp . HelloServer
java -cp . HelloClientIt gives warnings about using a Sun proprietary interface, but that's the only problem that I've had with the Java end. Getting the C end working has been more challenging. ORBit seems to have some serious interoperability problems. I haven't gotten it working yet with Java.