START THE NAMING SERVICE¶

You must start the Java IDL naming service before an application or applet that uses its naming service. Installation of the Java IDL product creates a script (Oracle Solaris: tnameserv) or executable file (Windows: tnameserv.exe) that starts the Java IDL naming service. Start the naming service so it runs in the background.

If you do not specify otherwise, then the Java IDL naming service listens on port 900 for the bootstrap protocol used to implement the ORB resolve_initial_references and list_initial_references methods, as follows:

tnameserv -ORBInitialPort nameserverport&

If you do not specify the name server port, then port 900 is used by default. When running Oracle Solaris software, you must become the root user to start a process on a port below 1024. For this reason, it is recommended that you use a port number greater than or equal to 1024. To specify a different port, for example, 1050, and to run the naming service in the background, from a UNIX command shell, enter:

tnameserv -ORBInitialPort 1050&

From an MS-DOS system prompt (Windows), enter:

start tnameserv -ORBInitialPort 1050

Clients of the name server must be made aware of the new port number. Do this by setting the org.omg.CORBA.ORBInitialPort property to the new port number when you create the ORB object.

RUN THE SERVER AND CLIENT ON DIFFERENT HOSTS¶

In most of the Java IDL and RMI-IIOP tutorials, the naming service, server, and client are all running on the development machine. In real-world deployment, the client and server probably run on different host machines from the Naming Service.

For the client and server to find the Naming Service, they must be made aware of the port number and host on which the naming service is running. Do this by setting the org.omg.CORBA.ORBInitialPort and org.omg.CORBA.ORBInitialHost properties in the client and server files to the machine name and port number on which the Naming Service is running. An example of this is shown in Getting Started Using RMI-IIOP at http://docs.oracle.com/javase/8/docs/technotes/guides/rmi-iiop/rmiiiopexample.html

You could also use the command-line options -ORBInitialPort nameserverport# and -ORBInitialHost nameserverhostname to tell the client and server where to find the naming service. For one example of doing this using the command-line option, see Java IDL: The Hello World Example on Two Machines at http://docs.oracle.com/javase/8/docs/technotes/guides/idl/tutorial/jidl2machines.html

For example, suppose the Transient Naming Service, tnameserv is running on port 1050 on host nameserverhost. The client is running on host clienthost, and the server is running on host serverhost.

Start tnameserv on the host nameserverhost:

tnameserv -ORBInitialPort 1050

Start the server on the serverhost:

java Server -ORBInitialPort 1050 -ORBInitialHost nameserverhost

Start the client on the clienthost:

java Client -ORBInitialPort 1050 -ORBInitialHost nameserverhost

STOP THE NAMING SERVICE¶

To stop the Java IDL naming service, use the relevant operating system command, such as kill for a Unix process or Ctrl+C for a Windows process. The naming service continues to wait for invocations until it is explicitly shut down. Note that names registered with the Java IDL naming service disappear when the service is terminated.

ADD OBJECTS TO THE NAME SPACE¶

The following example shows how to add names to the name space. It is a self-contained Transient Naming Service client that creates the following simple tree.

Initial Naming Context

     plans

     Personal

          calendar

          schedule

In this example, plans is an object reference and Personal is a naming context that contains two object references: calendar and schedule.

import java.util.Properties;

import org.omg.CORBA.*;

import org.omg.CosNaming.*;

public class NameClient {

    public static void main(String args[]) {

        try {

In Start the Naming Service, the nameserver was started on port 1050. The following code ensures that the client program is aware of this port number.

            Properties props = new Properties();

            props.put("org.omg.CORBA.ORBInitialPort", "1050");

            ORB orb = ORB.init(args, props);

This code obtains the initial naming context and assigns it to ctx. The second line copies ctx into a dummy object reference objref that is attached to various names and added into the name space.

            NamingContext ctx =

                NamingContextHelper.narrow(

                    orb.resolve_initial_references("NameService"));

             NamingContext objref = ctx;

This code creates a name plans of type text and binds it to the dummy object reference. plans is then added under the initial naming context using the rebind method. The rebind method enables you to run this program over and over again without getting the exceptions from using the bind method.

            NameComponent nc1 = new NameComponent("plans", "text");

            NameComponent[] name1 = {nc1};

            ctx.rebind(name1, objref);

            System.out.println("plans rebind successful!");

This code creates a naming context called Personal of type directory. The resulting object reference, ctx2, is bound to the name and added under the initial naming context.

            NameComponent nc2 = new NameComponent("Personal", "directory");

            NameComponent[] name2 = {nc2};

            NamingContext ctx2 = ctx.bind_new_context(name2);

            System.out.println("new naming context added..");

The remainder of the code binds the dummy object reference using the names schedule and calendar under the Personal naming context (ctx2).

            NameComponent nc3 = new NameComponent("schedule", "text");

            NameComponent[] name3 = {nc3};

            ctx2.rebind(name3, objref);

            System.out.println("schedule rebind successful!");

            NameComponent nc4 = new NameComponent("calender", "text");

            NameComponent[] name4 = {nc4};

            ctx2.rebind(name4, objref);

            System.out.println("calender rebind successful!");

        } catch (Exception e) {

            e.printStackTrace(System.err);

        }

    }

}

BROWSING THE NAME SPACE¶

The following sample program shoes how to browse the name space.

import java.util.Properties;

import org.omg.CORBA.*;

import org.omg.CosNaming.*;

public class NameClientList {

    public static void main(String args[]) {

        try {

In Start the Naming Service, the nameserver was started on port 1050. The following code ensures that the client program is aware of this port number.

            Properties props = new Properties();

            props.put("org.omg.CORBA.ORBInitialPort", "1050");

            ORB orb = ORB.init(args, props);

The following code obtains the initial naming context.

            NamingContext nc =

            NamingContextHelper.narrow(

                orb.resolve_initial_references("NameService"));

The list method lists the bindings in the naming context. In this case, up to 1000 bindings from the initial naming context will be returned in the BindingListHolder; any remaining bindings are returned in the BindingIteratorHolder.

            BindingListHolder bl = new BindingListHolder();

            BindingIteratorHolder blIt= new BindingIteratorHolder();

            nc.list(1000, bl, blIt);

This code gets the array of bindings out of the returned BindingListHolder. If there are no bindings, then the program ends.

            Binding bindings[] = bl.value;

            if (bindings.length == 0) return;

The remainder of the code loops through the bindings and prints outs the names.

            for (int i=0; i < bindings.length; i++) {

                // get the object reference for each binding

                org.omg.CORBA.Object obj = nc.resolve(bindings[i].binding_name);

                String objStr = orb.object_to_string(obj);

                int lastIx = bindings[i].binding_name.length-1;

                // check to see if this is a naming context

                if (bindings[i].binding_type == BindingType.ncontext) {

                    System.out.println("Context: " +

                        bindings[i].binding_name[lastIx].id);

                } else {

                    System.out.println("Object: " +

                        bindings[i].binding_name[lastIx].id);

                }

            }

        } catch (Exception e) {

            e.printStackTrace(System.err)

        }

    }

}