• Object Implementation
• Activating Objects Directly
• The Basic Object Adaptor
• Object and Implementation Deactivation

Persistent Object References

You can use persistent object references to implement long-running services that provide long-term tasks. Light-weight and domain-specific, transient object references take a relatively short amount of time to instantiate. Persistent object references take longer to instantiate. Consequently, the ideal mix is to have some persistent object references and many more transient object references used by your application. The following code example creates and registers a persistent object reference using the name ISB_Bank.

Creating a persistent object.

// Using Enterprise Server's ORB
public class Server {
  public static void main(String[] args) {
    try {
      // Initialize the ORB.
      org.omg.CORBA.ORB orb = org.omg.CORBA.ORB.init();
      // Initialize the BOA.
      org.omg.CORBA.BOA boa = orb.BOA_init();
      // Create the account manager object.
      AccountManager manager = new AccountManager("ISB_Bank");
      // Export the newly created object.
      boa.obj_is_ready(manager);
      String host = java.netInetAddress.getLocalHost().getHostName();
      netscape.WAI.Naming.register
         ("http://" + host + "/ISB_Bank", manager);

      // Or, if using Communicator's ORB, the call would be:
      // netscape.WAI.Naming.register
      //    ("http://" + host + "/NameService/ISB_Bank", manager);

      // Wait for incoming requests
      boa.impl_is_ready();
    } catch(org.omg.CORBA.SystemException se) {
        System.err.println(se);
    }
      catch(java.net.UnknownHostException u) {
        System.err.println(u);
    }
  }
}

Transient Object References

Creating a transient object.

// Using Enterprise Server's ORB
public class Server {
  public static void main(String[] args) {
    try {
      // Initialize the ORB.
      org.omg.CORBA.ORB orb = org.omg.CORBA.ORB.init();
      // Initialize the BOA.
      org.omg.CORBA.BOA boa = orb.BOA_init();
      // Create the account manager object.
      AccountManager manager = new AccountManager(); 
      // Export the newly created object.
      boa.obj_is_ready(manager);
      String host = java.netInetAddress.getLocalHost().getHostName();
      netscape.WAI.Naming.register
         ("http://" + host + "/ISB_Bank", manager);

      // Or, if using Communicator's ORB, the call would be:
      // netscape.WAI.Naming.register
      //    ("http://" + host + "/NameService/ISB_Bank", manager);

      // Wait for incoming requests
      boa.impl_is_ready();
    } catch(org.omg.CORBA.SystemException se) {
        System.err.println(se);
    }
      catch(java.net.UnknownHostException u) {
        System.err.println(u);
    }
  }
}

The obj_is_ready method notifies the BOA that a particular ORB object is ready to receive requests from client applications. If your server offers more than one ORB object, it must invoke obj_is_ready for each object, passing the object reference as an argument.

If a persistent object reference is passed to obj_is_ready, the BOA will register the object with the naming service. If the reference is transient, no such registration will occur. If obj_is_ready has not been invoked for an object by its server and a client attempts to bind to the object, the exception NO_IMPLEMENT is raised.

Once all of the objects have been instantiated and all the invocations of obj_is_ready have been made, the server must invoke the impl_is_ready method to enter an event loop and await client requests. Servers that are activated through a GUI (graphical user interface) or are activated by other means do not need to use impl_is_ready.

Activating Objects Directly

NOTE: The method BOA.obj_is_ready must be called for each object offered by the implementation.

// Using Enterprise Server's ORB
public class Server {
  public static void main(String[] args) {
    try {
      // Initialize the ORB.
      org.omg.CORBA.ORB orb = org.omg.CORBA.ORB.init();
      // Initialize the BOA.
      org.omg.CORBA.BOA boa = orb.BOA_init();
      // Create the account manager object for Chicago.
      AccountManager chicago = new AccountManager("Chicago");
      // Create the account manager object for Dallas.
      AccountManager dallas = new AccountManager("Dallas");
      // Export the newly created objects.
      boa.obj_is_ready(chicago);
      boa.obj_is_ready(dallas);
      System.out.println(chicago + " is ready.");
      System.out.println(dallas + " is ready.");
      String host = java.netInetAddress.getLocalHost().getHostName();

      // Or, if using Communicator's ORB, the call would be:
      // netscape.WAI.Naming.register
      //    ("http://" + host + "/NameService/bank", chicago);

      netscape.WAI.Naming.register("http://" + host + "/bank", chicago);
      netscape.WAI.Naming.register("http://" + host + "/bank", dallas);

      // Wait for incoming requests
      boa.impl_is_ready();
    } catch(org.omg.CORBA.SystemException se) {
        System.err.println(se);
    }
      catch(java.net.UnknownHostException u) {
        System.err.println(u);
    }
  }
}

A service can reside in the same process as its client or it can reside in a separate process called a server. Servers can contain and offer one or more services. Furthermore, they can be activated by the BOA on demand or they can be started by some entity external to the BOA.

Object and Implementation Deactivation

Service implementations that called obj_is_ready can be deactivated explicitly by calling deactivate_obj. Then, the implementation will not be available to service client requests. The service can only be re-activated if it is restarted or if it again calls obj_is_ready.

Last Updated: 02/04/98 13:46:53