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Java IDL: Interoperable Naming Service (INS) Example - JDK 5 Documentation v1.4.1, Java 2 SDK 英文文档

Java IDL: Interoperable Naming Service (INS) Example

The Interoperable Naming Service (INS) is an extension to the CosNaming service. It provides the following additional features:

The following diagram shows how INS fits into ORBD:

ORBD



An object reference contains at least three pieces of information: an address, the name of the POA that created an object reference, and an Object ID.

Using INS, you can provide an URL to access the CORBA object, which is more readable than a stringified Interoperable Object References (IOR). The following stringified object reference formats are allowed:

NamingContextExt API

The NamingContextExt interface, derived from NamingContext provides the operations required to use URLs and stringified names. Some of the APIs in NamingContextExt for converting between CosNames, Stringified Names, and URLs are listed below. See the COS Naming Specification, Section 3.6.4, for more information on these API.

Conversions from URLs to objects are handled by org.omg.CORBA.ORB.string_to_object() as described in the CORBA 2.3 Specification, Section 13.6.6.

The following Java IDL tutorials use NamingContextExt:

Bootstrap Options for the ORB

The ORB can be configured to return the handle of a customized CORBA service from resolve_initial_references() using either ORBInitRef and/or ORBDefaultInitRef. For example,

The order of resolution when these options are used is as follows:

  1. Objects registered with register_initial_references
  2. -ORBInitRef
  3. -ORBDefaultInitRef
  4. Proprietary Bootstrap (Sun ORBs only)

For more information about INS, refer to the OMG specification at (ptc/00-08-07).

INS Example: Publishing a Reference to be Accessed by INS URL's

This document is a high-level overview of how to create a complete CORBA (Common Object Request Broker Architecture) application using the Interoperable Naming Service (INS).

This example makes use of the following files:

Each step in the tutorial is indicated by this symbol.

Defining the Interface (Service.idl)

The first step to creating a CORBA application is to specify all of your objects and their interfaces using the OMG's Interface Definition Language (IDL).

The following code is written in the OMG IDL, and describes a CORBA object whose ping() operation pings the INS Service.

Create the file Service.idl and add the following code:

Service.idl 

// A very simple interface to explain this example
interface Service {
    void ping();
};

Implementing the Server (INSServer.java)

The INSServer class has the server's main() method, which:

Create the file INSServer.java and add the following code:

INSServer.java 

// INSServer.java
// Copyright and License 
import java.util.Properties;
import org.omg.CORBA.Object;
import org.omg.CORBA.ORB;
import org.omg.CORBA.Policy;
import org.omg.PortableServer.POA;
import org.omg.PortableServer.*;
import org.omg.PortableServer.Servant;

public class INSServer {
    public static void main( String args[] ) {
        try {
            Properties properties = System.getProperties( );
            // STEP 1: Set ORBPeristentServerPort property
            // Set the proprietary property to open up a port to listen to
            // INS requests. 
            // Note: This property is subject to change in future releases
            properties.put( "com.sun.CORBA.POA.ORBPersistentServerPort",
                Integer.toString(1060) );

            // STEP 2: Instantiate the ORB, By passing in the 
            // ORBPersistentServerPort property set in the previous step
            ORB orb = ORB.init( args, properties );


            // STEP 3: Instantiate the Service Object that needs to be published
            // and associate it with RootPOA.
            ServiceImpl servant = new ServiceImpl( );
            POA rootPOA = POAHelper.narrow( orb.resolve_initial_references( "RootPOA" ));
            rootPOA.the_POAManager().activate();
            rootPOA.activate_object( servant );

            // STEP 4: Publish the INS Service using 
            // orb.register_initial_reference( <ObjectKey>, <ObjectReference> 
            // NOTE: Sun private internal API, not part of CORBA 2.3.1.
            // May move as our compliance with OMG standards evolves.
            ((com.sun.corba.se.internal.Interceptors.PIORB) orb).
                register_initial_reference( 
                "PingService", rootPOA.servant_to_reference(servant) );

            System.out.println( "INS Server is Ready..." );
             
            // STEP 5: We are ready to receive requests
            orb.run( );
        } catch ( Exception e ) {
             System.err.println( "Error in setup : " + e );
        }
    } 
}
 

Implementing the Service (ServiceImpl.java)

The example implementation, ServiceImpl, is the implementation of the Service IDL interface.

Create the file ServiceImpl.java and add the following code:

ServiceImpl.java 

// ServiceImpl.java
// Copyright and License 

// Implementation of Service interface
public class ServiceImpl extends ServicePOA {
    public void ping( ) {
        System.out.println( "PingService.ping called..." );
    }
}

Implementing the Client Application (INSClient.java)

The example application client that follows:

Create the file INSClient.java and add the following code:

INSClient.java 

// INSClient.java
// Copyright and License 
 
import org.omg.CORBA.ORB;

public class INSClient {
    public static void main( String args[] ) {
        try {
            // STEP 1: Instantiate the ORB
            ORB orb = ORB.init( args, null );

            // STEP 2: Resolve PingService using orb.resolve_initial_references()
            // In this example we have used -ORBInitRef argument to locate the
            // PingService. User can also choose to pass the corbaloc: url to
            // orb.string_to_object to resolve the published PingService 
            // reference.
            org.omg.CORBA.Object object = orb.resolve_initial_references(
                "PingService" );

            // STEP 3: Narrow the reference and we are ready to invoke method
            // on PingService.
            Service insService = ServiceHelper.narrow( object );

            insService.ping( );
            System.out.println( "The server has been pinged" );
            
        } catch ( Exception e ) {
            System.err.println( "Exception in INSClient " + e );
            e.printStackTrace( );
        }
    }
}
 

Building and Running the INS Example

When running this example, we recommend that you use a port number greater than or equal to 1024. This is because you must become root to start a process on a port under 1024 when using Solaris software. The ORBPersistentServerPort property of the server has been set to 1060 in this example.

Compile the Interface Definition

Change to the directory that contains the file Service.idl, and run the IDL-to-Java compiler as shown below: 

  idlj -fall  Service.idl

You must use the -fall option with the idlj compiler to generate both client and server-side bindings. For more information on the idlj options, link to IDL-to-Java compiler options.

The files generated by the idlj compiler for Service.idl, with the -fall command line option, are:

Compile the Java files

Compile the .java files, including the stubs and skeletons, as follows: 

   javac *.java

Start the INS Server

Start the INS server: 

  java -classpath . INSServer

If the INS Server is running correctly, the following message will display: 

INS Server is Ready...

Start the Client Application

Open another terminal window or DOS shell and run the client application:

  java -classpath . INSClient -ORBInitRef 
    PingService=corbaloc:iiop:1.2@localhost:1060/PingService

When the client is run with the -ORBInitRef option, it will be able to locate PingService. The following message displays in the client window: 

The server has been pinged

And the following message displays in the server window: 

PingService.ping called...

When you have finished this tutorial, be sure to shut down or kill the INS server. To do this from a DOS prompt, select the window that is running the server and enter Ctrl+C to shut it down. To do this from a Unix shell, open the shell that was running the client and type pkill INSServer.

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