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J2SE 1.4 breathes new life into the CORBA community, Part 3

Create enterprise-level apps with the POA

By Tarak Modi, JavaWorld.com, 10/25/02

Page 7 of 7

  // Create the AccountPOA and set its default servant (NON_RETAIN Policy)
  policies[0] = 
rootPOA.create_lifespan_policy(LifespanPolicyValue.PERSISTENT);
  policies[1] = 
    rootPOA.create_request_processing_policy(RequestProcessingPolicyValue.
          USE_DEFAULT_SERVANT);
  policies[2] = rootPOA.create_servant_retention_policy(ServantRetentionPolicyValue.
          NON_RETAIN);
  POA accountPOA = rootPOA.create_POA("AccountPOA",null,policies);
  AccountDefaultServantImpl defaultAcc = new bank.AccountDefaultServantImpl();
  rootPOA.activate_object(defaultAcc);
  accountPOA.set_servant(defaultAcc);

Use servertool to register the CORBA servers

Since the bank and account object references are persistent references, J2SE 1.4 requires me to register my server implementations using servertool, which comes bundled with J2SE 1.4. The relevant commands are shown below. Note that these commands assume that J2SE 1.4 is installed on the E drive in a folder called j2sdk1.4.0_01 and that the bank example source code is compiled into the E:\dev\Corba\Bank\classes directory:

orbd -ORBInitialPort 1050 -ORBInitialHost localhost
E:\j2sdk1.4.0_01\bin\servertool.exe orbd -ORBInitialPort 1050 -ORBInitialHost localhost
register -server bank.BankServer -applicationName BankServer -classpath E:\dev\Corba\Bank    classes -args "-ORBInitialPort 1050 -ORBInitialHost localhost"
register -server bank.BankServer2 -applicationName BankServer2 -classpath E:\dev\Corba\Bank\classes -args "-ORBInitialPort 1050 -ORBInitialHost localhost"
register -server bank.BankServer3 -applicationName BankServer3 -classpath E:\dev\Corba\Bank\classes -args "-ORBInitialPort 1050 -ORBInitialHost localhost"

As shown in the code above, I start ORBD (Object Request Broker Daemon), which is the J2SE 1.4 persistent naming service, and then use servertool to register BankServer, BankServer2, and BankServer3. Each registration command requires me to provide the classpath and any startup command-line parameters. Obviously, you will have to compile the Java source code before you can register. Compiling (running idlj and javac) the bank application proves no different from compiling Part 2's Hello World application. So I'll leave that as an exercise for you.

A test client

BankClient, shown below, is a generic client that can access and test all three solutions discussed above:

package bank.test;
import bank.Bank;
import bank.BankHelper;
import bank.Account;
import bank.AccountHelper;
import bank.AccountInformation;
import bank.AccountType;
import org.omg.CORBA.*;
import org.omg.CosNaming.*;
import org.omg.CosNaming.NamingContextPackage.*;
public class BankClient
{
  public static void main(String args[])
  {
    try
    {
      // Create and initialize the ORB
        ORB orb = ORB.init(args, null);
      // 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 = "BankServer";
      System.out.println(args.length);
      if(args.length == 5)
        name = args[4];
      Bank theBank = BankHelper.narrow(ncRef.resolve_str(name));
      System.out.println("Obtained a handle on server object: " + theBank);
      AccountInformation accInfo = new AccountInformation();
      accInfo.accNum="";
      accInfo.accType = AccountType.NIL;
      Account[] accounts = theBank.findAccounts(accInfo);
      for(int i=0; i<accounts.length; i++)
        System.out.println("Account Number " + ((Account)accounts[i]).accountNumber());
      accounts[0].deposit((float)1.1);
    }
    catch(bank.UnknownException e)
    {
      System.out.print(e.reason);
    }
    catch(bank.InvalidOperationException e)
    {
      System.out.print(e.reason);
    }
    catch (Exception e)
    {
      System.out.println("ERROR : " + e) ;
        e.printStackTrace(System.out);
    }
  }
}

The program takes one parameter: the server to access, which is BankServer, BankServer2, or BankServer3. The default is BankServer. This parameter is actually the fifth one on the command line since the first four are J2SE 1.4 ORB-related parameters as shown in the example command line below:

  java test.BankClient -ORBInitialHost localhost -ORBInitialPort 1050 BankServer2

The program then finds all accounts and deposits .10 in the first account found. So, before you run this program, ensure you have at least one account in your database.

Until next time

As promised, this article has been hands-on, with wide coverage of various POA programming aspects. Based on the knowledge gained from Parts 2 and 3 of this series, you should be in a good position to start using the POA in your own projects. I will conclude the series in Part 4, another hands-on article, where I cover two important topics: the Interoperable Naming Service and portable interceptors.

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