module poaBank
{
interface Account
{
| exception InsufficientFunds {};
|
| float deposit(in float sum);
|
| float withdraw(in float sum) raises (InsufficientFunds);
|
| readonly attribute float balance;
};
interface Bank
{
| exception noSuchAccount {};
|
| Account getAccount(in long accountNum) raises (noSuchAccount);
};
};
package poaBankSrvntMgr;
import util.Util;
import org.omg.CORBA.ORB;
import org.omg.CORBA.Policy;
import org.omg.CosNaming.NameComponent;
import org.omg.CosNaming.NamingContext;
import org.omg.CosNaming.NamingContextHelper;
import org.omg.CosNaming.NamingContextPackage.NotFound;
import org.omg.PortableServer.POA;
import org.omg.PortableServer.Servant;
import org.omg.PortableServer.LifespanPolicyValue;
import org.omg.PortableServer.IdAssignmentPolicyValue;
import poaBank.Bank;
import poaBank.BankHelper;
public class Server
{
public static void main(String[] args)
{
| try {
| |
| | // create the jBroker ORB
| | ORB orb = ORB.init(args, null);
| |
| | // get the root POA
| | POA rootPOA = (POA) orb.resolve_initial_references("RootPOA");
| |
| | // create a persistent user assigned ids POA
| | POA bankPOA = rootPOA.create_POA("bankPOA",
| | rootPOA.the_POAManager(),
| | new Policy[] {
| | | rootPOA.create_id_assignment_policy(
| | | IdAssignmentPolicyValue.USER_ID),
| | | rootPOA.create_lifespan_policy(
| | | LifespanPolicyValue.PERSISTENT)
| | });
| |
| | // create and activate the bank servant
| | Servant bank = new BankImpl(bankPOA, args[0]);
| | bankPOA.activate_object_with_id("bank".getBytes(), bank);
| |
| | // get the root of the NameService
| | NamingContext root = NamingContextHelper.narrow(
| | orb.resolve_initial_references("NameService"));
| |
| | // if not done before, publish the bank objref
| | NameComponent nc = new NameComponent("bank2", "");
| | NameComponent[] name = new NameComponent[] { nc };
| | try {
| | | root.resolve(name);
| | } catch (NotFound ex) {
| | | // create the bank objref
| | | Bank bankObj = BankHelper.narrow(bankPOA.
| | | create_reference_with_id("bank".getBytes(),
| | | bank._all_interfaces(null, null)[0]));
| | | System.out.println(orb.object_to_string(bankObj));
| | | root.rebind(name, bankObj);
| | }
| |
| | // activate bankPOA
| | bankPOA.the_POAManager().activate();
| |
| | // wait for invocations
| | System.out.println("waiting for invocations ...");
| | orb.run();
| |
| } catch (Exception ex) {
| | ex.printStackTrace();
| }
}
}
package poaBankSrvntMgr;
import java.io.File;
import org.omg.CORBA.Policy;
import org.omg.PortableServer.POA;
import org.omg.PortableServer.Servant;
import org.omg.PortableServer.IdAssignmentPolicyValue;
import org.omg.PortableServer.ServantRetentionPolicyValue;
import org.omg.PortableServer.RequestProcessingPolicyValue;
import poaBank.BankPOA;
import poaBank.Account;
import poaBank.AccountImpl;
import poaBank.AccountHelper;
import poaBank.BankPackage.noSuchAccount;
public class BankImpl extends BankPOA
{
POA _acctPOA;
String _acctRepId; // repository Id for Account Objects
BankImpl(POA bankPOA, String dir) throws Exception
{
| // make sure that the DB dir exists
| File dbDir = new File (dir);
| if (!dbDir.exists()) dbDir.mkdir();
|
| // create the POA for Transient Account Objects
| _acctPOA = bankPOA.create_POA("acctPOA", bankPOA.the_POAManager(),
| new Policy[] {
| | bankPOA.create_id_assignment_policy(
| | IdAssignmentPolicyValue.USER_ID),
| | bankPOA.create_servant_retention_policy(
| | ServantRetentionPolicyValue.NON_RETAIN),
| | bankPOA.create_request_processing_policy(
| | RequestProcessingPolicyValue.USE_SERVANT_MANAGER)
| });
|
| // set the servant manager in Acct POA
| _acctPOA.set_servant_manager(new AccountServantMgr(dbDir));
|
| // compute the repository id for Account objects
| _acctRepId = new AccountImpl()._all_interfaces(null, null)[0];
}
public Account getAccount(int acctNum) throws noSuchAccount
{
| Account account = null;
|
| if ((acctNum >= 100) && (acctNum < 110)) {
| |
| | // construct the object id for account
| | byte objectId[] = new byte[1];
| | objectId[0] = (byte) ( acctNum & 0xFF);
| |
| | try {
| | | account = AccountHelper.narrow(_acctPOA.
| | | create_reference_with_id(objectId, _acctRepId));
| | } catch (Exception ex) {
| | | // org.omg.PortableServer.POAPackage.WrongPolicy
| | | // thrown on JDK 1.2 and 1.3
| | | ex.printStackTrace();
| | }
| }
|
| if (account == null) throw new noSuchAccount();
|
| return account;
}
}
The Servant Manager could also implement a cache instead of a table where it would time out servants. Using this approach you can literally support a very large number of objects.
package poaBankSrvntMgr;
import java.io.File;
import java.util.Hashtable;
import org.omg.CORBA.Policy;
import org.omg.CORBA.BAD_OPERATION;
import org.omg.CORBA.portable.ObjectImpl;
import org.omg.PortableServer.POA;
import org.omg.PortableServer.Servant;
import org.omg.PortableServer.ForwardRequest;
import org.omg.PortableServer.ServantLocator;
import org.omg.PortableServer.POAPackage.WrongPolicy;
import org.omg.PortableServer.IdAssignmentPolicyValue;
import org.omg.PortableServer.RequestProcessingPolicyValue;
import org.omg.PortableServer.ServantLocatorPackage.CookieHolder;
import poaBank.Account;
import poaBank.AccountImpl;
public class AccountServantMgr extends ObjectImpl
implements ServantLocator
{
File _dbDir;
Hashtable _accounts;
AccountServantMgr(File dbDir)
{
| _dbDir = dbDir;
| _accounts = new Hashtable(19);
}
public Servant preinvoke(byte[] oid, POA adapter, String operation,
CookieHolder the_cookie) throws ForwardRequest
{
| Servant servant = null;
|
| // get the account number
| int acctNum = oid[0];
| Integer AcctNum = new Integer(acctNum);
|
| // get the account servant
| synchronized (_accounts) {
| | // see if the account is already active
| | servant = (Servant) _accounts.get(AcctNum);
| |
| | // activate the servant
| | if (servant == null) {
| | | servant = new AccountImpl(_dbDir, acctNum);
| | | _accounts.put(AcctNum, servant);
| | }
| }
|
| return servant;
}
public void postinvoke(byte[] oid, POA adapter, String operation,
java.lang.Object the_cookie, Servant the_servant)
{
}
// servant manager is locality constrained
public String[] _ids()
{
| throw new BAD_OPERATION();
}
}
package poaBank;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import org.omg.CORBA.PERSIST_STORE;
import poaBank.AccountPackage.InsufficientFunds;
public class AccountImpl extends AccountPOA
{
float _balance;
File _acctDb;
public AccountImpl() {}
public AccountImpl(File dir, int i)
{
| _acctDb = new File(dir, new Integer(i).toString());
| if (_acctDb.exists()) _balance = readBalance();
}
public synchronized float deposit(float sum)
{
| _balance += sum;
|
| writeBalance();
|
| return _balance;
}
public synchronized float withdraw(float sum) throws InsufficientFunds
{
| if ((_balance - sum) < 0) throw new InsufficientFunds();
|
| _balance -= sum;
|
| writeBalance();
|
| return _balance;
}
public synchronized float balance()
{
| return _balance;
}
void writeBalance()
{
| try {
| | FileOutputStream fos = new FileOutputStream(_acctDb);
| | ObjectOutputStream oos = new ObjectOutputStream(fos);
| |
| | oos.writeObject(new Float(_balance));
| |
| | oos.close();
| } catch (Exception ex) {
| | throw new PERSIST_STORE();
| }
}
float readBalance()
{
| try {
| | FileInputStream fis = new FileInputStream(_acctDb);
| | ObjectInputStream ois = new ObjectInputStream(fis);
| |
| | float balance = ((Float) ois.readObject()).floatValue();
| |
| | ois.close();
| |
| | return balance;
| } catch (Exception ex) {
| | throw new PERSIST_STORE();
| }
}
}
server.main=poaBankSrvntMgr.Server server.alias=bank2 server.classpath=/usr/local/jbroker30/examples/lib server.args=/usr/local/jbroker30/examples/src/poaBankSrvntMgr/db server.vmflags=-Djava.compiler=NONE
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