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JavaWorld.com > Java Standard Edition >

J2SE 1.4 breathes new life into the CORBA community, Part 1

Get started developing enterprise CORBA applications with the latest version of J2SE

By Tarak Modi, JavaWorld.com, 08/30/02

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Page 5 of 6

      idlj -fall Hello.idl


idlj is located in your J2SE 1.4 installation's bin directory. This compiler implements the CORBA IDL-to-Java mapping specifications. It produces some Java files as output, which I briefly describe below:

  • HelloPOA.java: The abstract class that our server object will extend
  • HelloHelper.java: Provides auxiliary functionality, notably the narrow() method required to cast CORBA object references to their proper types
  • HelloHolder.java: Used whenever the Hello interface (type) is an out or an inout parameter to a method defined in IDL
  • _HelloStub.java: The client stub, providing CORBA functionality for the client
  • Hello.java and HelloOperations.java: Together provide interfaces that contain the Java version of our IDL interface


Step 3: Implement the server application

As mentioned above, the implementation of the server application consists of two parts: one class that implements the methods from the server interface, and another class that hosts the server object and registers it with the ORB runtime and naming service: 

package hello;
import org.omg.CosNaming.*;
import org.omg.CosNaming.NamingContextPackage.*;
import org.omg.CORBA.*;
import org.omg.PortableServer.*;
import org.omg.PortableServer.POA;
import java.util.Properties;
class HelloImpl extends HelloPOA {
  private ORB orb;
  public void setORB(ORB orb_val) {
    orb = orb_val;
  }
  // Implement sayHello() method
  public String sayHello() {
    return "\nHello world !!\n";
  }
  // Implement shutdown() method
  public void shutdown() {
    orb.shutdown(false);
  }
}
public class HelloServer {
  public static void main(String args[]) {
    try{
      // Create and initialize the ORB
      ORB orb = ORB.init(args, System.getProperties());
      // Get reference to rootpoa 
      POA rootPOA = POAHelper.narrow(orb.resolve_initial_references("RootPOA"));      
      // Create servant and register it with the ORB
      HelloImpl helloImpl = new HelloImpl();
      helloImpl.setORB(orb);
      // Get object reference from the servant
      org.omg.CORBA.Object ref = rootPOA.servant_to_reference(helloImpl);
      Hello href = HelloHelper.narrow(ref);
      // Get the root naming context
      org.omg.CORBA.Object objRef =
          orb.resolve_initial_references("NameService");
      // Use NamingContextExt, which is part of the Interoperable
      // Naming Service (INS) specification
      NamingContextExt ncRef = NamingContextExtHelper.narrow(objRef);
      // Bind the Object reference in Naming
      String name = "Hello";
      NameComponent path[] = ncRef.to_name( name );
      ncRef.rebind(path, href);
    
      // Activate the POAManager
      rootPOA.the_POAManager().activate();
      System.out.println("HelloServer ready and waiting ...");
      System.out.println(orb.object_to_string(href));
      // Wait for invocations from clients
      orb.run();
    }
      catch (Exception e) {
        System.err.println("ERROR: " + e);
        e.printStackTrace(System.out);
      }
      System.out.println("HelloServer Exiting ...");
  }
}


Step 4: Create client applications to use the server

Here's a sample client to test the server:

package hello;
import org.omg.CosNaming.*;
import org.omg.CosNaming.NamingContextPackage.*;
import org.omg.CORBA.*;
import java.util.*;
public class HelloClient
{
  static Hello helloImpl;
  public static void main(String args[])
    {
      try{
        // Create and initialize the ORB.
        ORB orb = ORB.init(args, System.getProperties());
        // Get the root naming context.
        org.omg.CORBA.Object objRef =
          orb.resolve_initial_references("NameService");
        // Use NamingContextExt instead of NamingContext. This is
        // part of the Interoperable Naming Service.
        NamingContextExt ncRef = NamingContextExtHelper.narrow(objRef);
        // Resolve the Object reference in Naming.
        String name = "Hello";
        helloImpl = HelloHelper.narrow(ncRef.resolve_str(name));
        System.out.println("Obtained a handle on server object: " + helloImpl);
        System.out.println(helloImpl.sayHello());
        helloImpl.shutdown();
      } catch (Exception e) {          
        e.printStackTrace();
        }
    }
}


Compile the server and client Java source files. Start the naming service as follows:

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