Vakgroep Informatietechnologie - IBCN CORBA & RMI Design of Distributed Software

Vakgroep Informatietechnologie - IBCN

CORBA & RMIDesign of Distributed Software

2ODS – Introduction to CORBA & RMIVakgroep Informatietechnologie - IBCN

Objectives

After this lab session you should be able to Write client and server applications Devlop object-oriented based distributed systems Use the CORBA and Java RMI technology CORBA = Common Object Request Brokerage Architecture Language neutral technology Allowing software components on multiple computers to

communicate

Java RMI Java specific technology Allowing software components on multiple computers to

communicate

2

ODS – Introduction to CORBA & RMIVakgroep Informatietechnologie - IBCN

CORBA &

Java RMI

Distributed system

4ODS – Introduction to CORBA & RMIVakgroep Informatietechnologie - IBCN

Outline

1. CORBAHow to write a CORBA application

5ODS – Introduction to CORBA & RMIVakgroep Informatietechnologie - IBCN

Writing CORBA in 5 steps

Writing the IDL files

Writing the Server

Writing the Servant

Writing the Client

Starting the application

6ODS – Introduction to CORBA & RMIVakgroep Informatietechnologie - IBCN

Writing the IDL files

The IDL file describes Which classes can be accessed remotely The signature of each remote method

Compile the file: idlj –fall server.idl

module ods{

module corba{

module bmicalculator{

interface BMICalculator{

double calculateBMI(in double length, in double weight);

};

};

};

};

7ODS – Introduction to CORBA & RMIVakgroep Informatietechnologie - IBCN

Writing the Server

Several classes were generatedWriting the server

Extending the abstract POA class No CORBA specific code is needed

package ods.corba.bmicalculator;

public class BMICalculatorImpl extends BMICalculatorPOA{

public double calculateBMI(double length,

double weight){

return weight / (length * length);

}

}

8ODS – Introduction to CORBA & RMIVakgroep Informatietechnologie - IBCN

Writing the servant

Servant: main class to start the serverSteps to take:

Initialize the ORB (Object Request Broker)

Start the Server object

java.util.Properties props = System.getProperties(); props.put("org.omg.CORBA.ORBInitialPort”,157.193.214.253); props.put("org.omg.CORBA.ORBInitialHost", 1049);

ORB orb = ORB.init(new String[0], props);

BMICalculatorImpl bmi_calc = new BMICalculatorImpl();

9ODS – Introduction to CORBA & RMIVakgroep Informatietechnologie - IBCN

Writing the servant

Find the Naming Service & Root POA

Activate the Server object with the POA

POA rootPOA = POAHelper.narrow(orb.resolve_initial_references("RootPOA"));

NamingContext namingContext = NamingContextHelper.narrow(orb.resolve_initial_references

("NameService"));

rootPOA.activate_object(bmi_calc);

BMICalculator bmicalcRef = BMICalculatorHelper.

narrow(rootPOA.servant_to_reference(bmi_calc));

10ODS – Introduction to CORBA & RMIVakgroep Informatietechnologie - IBCN

Writing the servant

Register the server object with the Naming Service

Activate the POA and start the ORB

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NameComponent nc = new NameComponent("BMICalculator", ""); NameComponent path[] = { nc };

namingContext.rebind(path, bmicalcRef);

rootPOA.the_POAManager().activate();

orb.run();

11ODS – Introduction to CORBA & RMIVakgroep Informatietechnologie - IBCN

Writing the client

Steps to take: Initialize the ORB (Object Request Broker)

Find the Naming Service

java.util.Properties props = System.getProperties(); props.put("org.omg.CORBA.ORBInitialPort”,157.193.214.253); props.put("org.omg.CORBA.ORBInitialHost", 1049);

ORB orb = ORB.init(new String[0], props);

NamingContext namingContext = NamingContextHelper.narrow(orb.resolve_initial_references

("NameService"));

12ODS – Introduction to CORBA & RMIVakgroep Informatietechnologie - IBCN

Writing the client

Obtain a reference to the remote object

Invoke a method just as a regular object

NameComponent nc = new NameComponent("BMICalculator", ""); NameComponent path[] = { nc };

BMICalculator server = BMICalculatorHelper.narrow(ncRef.resolve(path));

System.out.println(server.calculateBMI(1.87, 75));

13ODS – Introduction to CORBA & RMIVakgroep Informatietechnologie - IBCN

Starting the application

Starting the Naming Service

Starting the Server

Starting the client

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start orbd –ORBInitialPort 1049

start java ods.corba.bmicalculator.

StartBMICalculatorServer 157.193.214.253 1049

java ods.corba.bmicalculator.client.BMICalculatorClient 157.193.214.253 1049

14ODS – Introduction to CORBA & RMIVakgroep Informatietechnologie - IBCN

Outline

2. Java RMIHow to write a Java RMI application

15ODS – Introduction to CORBA & RMIVakgroep Informatietechnologie - IBCN

Writing Java RMI in 5 steps

Writing the remote Java interface

Writing the Server

Writing the Servant

Writing the Client

Starting the application

Writing the policy file

16ODS – Introduction to CORBA & RMIVakgroep Informatietechnologie - IBCN

Writing the remote interface

Define the class as remote Extend Remote interface

Define the available remote methods Add “throws RemoteException”

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package ods.rmi.bmicalculator.server;

import java.rmi.Remote;

import java.rmi.RemoteException;

public interface BMICalculatorServerInterface extends Remote {

public double calculateBMI(double length, double weight)

throws RemoteException;

}

17ODS – Introduction to CORBA & RMIVakgroep Informatietechnologie - IBCN

Implementing the remote interface No specific Java RMI code is needed

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public class BMICalculatorServer implements ods.rmi.bmicalculator.server.BMICalculatorServerInterface{

public BMICalculatorServer() {

super();

}

public double calculateBMI(double length, double weight)

throws RemoteException {

return weight/(length*length);

}

}

Writing the Server

18ODS – Introduction to CORBA & RMIVakgroep Informatietechnologie - IBCN

Writing the servant

Servant: main class to start the serverSteps to take:

Initialize the Security Manager

Start the Server object

if (System.getSecurityManager() == null) {

System.setSecurityManager(new SecurityManager());

}

BMICalculatorServerInterface bmiCalc = new

BMICalculatorServer();

BMICalculatorServerInterface stub =

(BMICalculatorServerInterface)

UnicastRemoteObject.exportObject(bmiCalc, 0);

19ODS – Introduction to CORBA & RMIVakgroep Informatietechnologie - IBCN

Writing the servant

Register the server with the Registry

Registry registry = LocateRegistry.getRegistry();

String name = (args[0]==null)?args[0]:"BMICalculator";

registry.rebind(name, stub);

20ODS – Introduction to CORBA & RMIVakgroep Informatietechnologie - IBCN

Writing the client

Steps to take: Initialize the Security Manager

Obtain a reference to the remote object

Invoke a method

if (System.getSecurityManager() == null) {

System.setSecurityManager(new SecurityManager());

}

Registry registry = LocateRegistry.(args[0]);

BMICalculatorServerInterface calculator =

(BMICalculatorServerInterface)registry.lookup(args[1]);

System.out.println(calculator.calculateBMI(1.87, 75));

21ODS – Introduction to CORBA & RMIVakgroep Informatietechnologie - IBCN

Writing a policy file

Policy file needed to allow network communication

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grant{

permission java.net.SocketPermission "*:1024-65535", "connect,accept";

};

22ODS – Introduction to CORBA & RMIVakgroep Informatietechnologie - IBCN

Starting the application

Starting the Registry

Starting the Server

Starting the client

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rmiregistry [port]

start java -Djava.security.policy=java.policy ods.rmi.bmicalculator.server.BMICalculatorServer BMICalculator

java -Djava.security.policy=java.policy

ods.rmi.bmicalculator.client.BMIClientProgram

157.193.214.124 BMICalculator