MSc Course in Advanced Distributed Systems

Session 2.2: Practical CORBA Programming

http://info.comp.lancs.ac.uk/msc/ads/index.htm

Resources

• three problems: Echo, Time and Notifier

• http://www.comp.lancs.ac.uk/~leek/msc2004/ has problem specifications

• There are 3 problems, Echo, File and Chat

• we will now look at the Echo example in some detail to get you started...

The Echo files (online)

Echo.idl produces (mainly)...– EchoInterface.java. The IDL interface represented as a Java

interface.

– _EchoInterfaceImplBase.java. It implements the

FileInterface.java interface – _EchoStub.java. The Stub.

• Client.java. The Client Implementation

• Server.java. The Server Implementation

Echo.idl

//// Echo.idl//

/// Put the interface in a module to avoid global namespace pollution

module Exercise{ // A very simple interface interface EchoServer { // Return the given string string echo(in string s); };};

server.java 1 (of 2)// server.java, stringified object reference versionimport java.io.*;import org.omg.CORBA.*;

class EchoServant extends _EchoImplBase { public String echo(String s) {

return s; }}public class server {

public static void main(String args[]) {

try{ // create and initialize the ORB ORB orb = ORB.init(args, null);

// create servant and register it with the ORB EchoServant echoRef = new EchoServant(); orb.connect(echoRef);

server.java 2 (of 2)// stringify the EchoRef and dump it in a file String str = orb.object_to_string(echoRef); String filename = System.getProperty("user.home")+ System.getProperty("file.separator")+"EchoIOR"; FileOutputStream fos = new FileOutputStream(filename); PrintStream ps = new PrintStream(fos); ps.print(str); ps.close();

// wait for invocations from clients java.lang.Object sync = new java.lang.Object(); synchronized (sync) { sync.wait(); }

} catch (Exception e) { System.err.println("ERROR: " + e); e.printStackTrace(System.out);}

}}

client.java 1 (of 2)

// client.java, stringified object reference version

import java.io.*;

import org.omg.CORBA.*;

public class client

{

public static void main(String args[])

{

try{

// create and initialize the ORB

ORB orb = ORB.init(args, null);

// Get the stringified object reference and destringify it.

String filename = System.getProperty("user.home")+

System.getProperty("file.separator")+"echoIOR";

BufferedReader br = new BufferedReader(new FileReader(filename));

client.cpp 2 (of 2)

String ior = br.readLine();

org.omg.CORBA.Object obj = orb.string_to_object(ior);

Echo echoRef = EchoHelper.narrow(obj);

// call the Echo server object and print results

String echo = echoRef.echo("Hello, World");

System.out.println(echo);

} catch (Exception e) {

System.out.println("ERROR : " + e) ;

e.printStackTrace(System.out);

}

}

}

Running the application

Follow the instructions on the web site to download the pre-compiled classes.

• running– run the server first: ‘java server’– then run the client: ‘java server’