This guide walks you through creating a simple CORBA application in Java, where a client communicates with a server to receive a message. We'll use Java 1.8 to implement CORBA (Common Object Request Broker Architecture) and define an IDL (Interface Definition Language) interface to facilitate communication between the client and server.
The goal of this lab is to design, develop, and test a banking application that manages an account, specifically allowing the following operations:
- Reading the account balance
- Crediting the account
- Debiting the account
The client will interact with the application via the menu below, which will enable them to execute these various operations. CORBA objects will be implemented through inheritance.
+---------------------------+
| Banking Service |
+---------------------------+
| 1 : Read account balance |
| 2 : Credit the account |
| 3 : Debit the account |
| 0 : Exit |
+---------------------------+
Type the operation code to perform:
- banque.idl: Interface of the Banking application
- server.java: Implementation of the Banking application server (inheritance version)
- client_banque.java: Implementation of the Banking application client
- impl_compte_heritage.java: Implementation of the Account object in the Banking application (inheritance version)
- Compile the IDL file:
idlj -fall banque.idl
- Develop the client and server.
- Compile the client, server, and files generated by the IDL compiler:
javac banque/*.java - Start the server:
java banque.Server
- Run the client:
java banque.client_banque
- Java 1.8 must be installed on your machine.
- CORBA IDL Compiler (
idlj) must be available.
Ensure you have Java 1.8 installed on your system. You can download it from the official Oracle archive:
- Install Java by following the instructions on the website.
- After installation, add the bin folder to your system's
PATH. This allows Java and CORBA tools likeidljto be executed from the command line.
Example PATH:
C:\Program Files\Java\jdk1.8.0_202\bin
Check if idlj (the IDL compiler) is available by running the following command in your terminal or command prompt:
idlj -versionIf the command runs successfully and shows the version, you're ready to proceed.
Create a new file named banque.idl. This file defines the CORBA interface, which will be used for communication between the client and server.
interface Compte {
double solde();
boolean credit(in double amount);
boolean debit(in double amount);
};Use the CORBA IDL compiler to generate the necessary classes for both client and server communication.
Run the following command:
idlj -fall hello.idl- A new directory named
hellowill be created. - Several Java classes will be generated. These include stubs and skeletons necessary for CORBA communication.
Make sure to open and review the generated files to understand the communication structure.
Now that the IDL has been compiled, implement the server and client in Java. Use the generated classes to handle CORBA object communication.
public class impl_compte_heritage extends ComptePOA{
double solde;
impl_compte_heritage(double solde){
this.solde = solde;
}
@Override
public double solde() {
return solde;
}
@Override
public boolean credit(double amount) {
if (amount >= 0) {
this.solde = this.solde + amount;
return true;
}
return false;
}
@Override
public boolean debit(double amount) {
if (amount <= solde) {
this.solde = this.solde - amount;
return true;
}
return false;
}
}public class server {
public static void main(String[] args) {
Properties props = System.getProperties();
int status = 0;
ORB orb = null;
try {
orb = ORB.init(args, props);
status = run(orb);
} catch (Exception ex) {
ex.printStackTrace();
status = 1;
}
if (orb != null) {
try {
orb.destroy();
} catch (Exception ex) {
ex.printStackTrace();
status = 1;
}
}
System.exit(status);
}
static int run(ORB orb) throws UserException, IOException {
POA rootPOA;
POAManager manager;
rootPOA = POAHelper.narrow(orb.resolve_initial_references("RootPOA"));
manager = rootPOA.the_POAManager();
impl_compte_heritage compte_impl = new impl_compte_heritage(5000);
Compte compte = compte_impl._this(orb);
String ref = orb.object_to_string(compte);
String refFile = "reference";
try (FileOutputStream file = new FileOutputStream(refFile);
PrintWriter out = new PrintWriter(file)) {
out.println(ref);
System.out.println("server en attente des clients\nRef: "+ref);
} catch (Exception ignored) {}
try {
if (manager != null) {
manager.activate();
}
orb.run();
} catch (Exception e) {
e.printStackTrace();
return 1;
}
return 0;
}
}public class ClientBanque {
public static void main(String[] args) {
Properties props = System.getProperties();
int status;
ORB orb = null;
try {
orb = ORB.init(args, props);
status = run(orb);
} catch (Exception ex) {
ex.printStackTrace();
status = 1;
}
if (orb != null) {
try {
orb.destroy();
} catch (Exception ex) {
ex.printStackTrace();
status = 1;
}
}
System.exit(status);
}
static int run(ORB orb) throws IOException {
Object obj;
String refFile = "reference";
try (FileInputStream file = new FileInputStream(refFile);
BufferedReader in = new BufferedReader(new InputStreamReader(file))) {
String ref = in.readLine();
obj = orb.string_to_object(ref);
Compte compte = CompteHelper.narrow(obj);
int choice;
double amount = 0.0;
Scanner scanner = new Scanner(System.in);
// Display menu
System.out.println("+---------------------------+");
System.out.println("| Service bancaire |");
System.out.println("+---------------------------+");
System.out.println("1 : Lecture du montant du compte");
System.out.println("2 : Crédit du compte");
System.out.println("3 : Débit du compte");
System.out.println("0 : Quitter");
do {
choice = scanner.nextInt();
switch (choice) {
case 1:
System.out.println("Lecture du montant du compte");
System.out.println(compte.solde());
break;
case 2:
System.out.println("Crédit du compte");
System.out.println("Taper le montant: ");
amount = scanner.nextDouble();
System.out.println(compte.credit(amount));
break;
case 3:
System.out.println("Débit du compte");
System.out.println("Taper le montant: ");
amount = scanner.nextDouble();
System.out.println(compte.debit(amount));
break;
case 0:
System.out.println("Quitter");
break;
default:
System.out.println("Choix invalide, veuillez réessayer.");
}
} while (choice != 0);
}
return 0;
}
}After implementing both the client and server:
-
Run the server:
- Open a terminal and execute the following command:
java server
-
Run the Client:
- Open another terminal and execute the following command:
java Client
If everything is set up correctly, the client will print Hello from the server! to the console.
This guide showed how to implement a simple CORBA-based client-server system in Java. By following these steps, you've defined a CORBA interface, compiled the necessary Java classes, implemented the server and client, and executed the communication between them.