By Dr. Jiang B. Liu

1. Java Computing By Dr. Jiang B. Liu 11. Java IDL and CORBA Generic ORB Core idltojava development tool CORBA Object Service (COS) name service - nameserv Java IDL Hello Example

2. Java IDL Network Computing • Java IDL provides connectivity and interoperability to the OMG CORBA standard. • IDL: specifies interfaces for objects (services,components, etc...) available anywhere in a network. The IDL definitions can be compiled with the idltojava stub generator tool to generate Java interface definitions and Java client and server stubs. • IIOP is a CORBA network protocol. Java IDL uses IIOP version 1.0 and it is based on a portable Java ORB core.

3. Network Computing: CORBA • CORBA network component computing model

4. Java IDL Client Invocation Model • An Object Invocation from a JavaIDL Client

5. ORB Client Invocation Model • The Structure of Object Request Broker Interfaces

6. OMG IDL Client Invocation Model • OMG Interface and Implementation Repositories

7. Java IDL Example: Hello.idl • Idl file module HelloApp { interface hello { string sayHello(); }; }; • Generate Java stubs idltojava -fno-cpp -fclient -fserver -fverbose hello.idl (Generate the following interfaces/classes in the HelloApp directory hello.java - interface (client/server) helloHolder.java - Holder class for each interface providing out/inout parameter passing modes. (not used in this example) helloHelper.java - Helper class for for each interface providing static methods such as read, write, insert, extract, id. (client) _helloImplBase - Implementation base (server) -helloStub - Stub (client/server)

8. Java IDL Example: Hello.idl • Start CORBA Object Service (COS) name service nameserv -ORBInitialPort 1050 • Compile and run Hello server object javac helloServer.java helloServant.java HelloApp\_helloImplBase.java HelloApp\_helloStub.java HelloApp\hello.java java helloServer -ORBInitialPort 1050 • Compile and run Hello client object javac helloClient.java HelloApp\helloHelper.java HelloApp\_helloStub.java HelloApp\hello.java java helloClient -ORBInitialPort 1050

9. Java IDL Example: Hello.idl • import HelloApp.*; • import org.omg.CosNaming.*; • import org.omg.CosNaming.NamingContextPackage.*; • import org.omg.CORBA.*; • class helloServant extends _helloImplBase • { • public String sayHello() • { • return "\nHello world !!\n"; • } • }

10. public class helloServer { • 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 • helloServant helloRef = new helloServant(); orb.connect(helloRef); • // get the root naming context • org.omg.CORBA.Object objRef = • orb.resolve_initial_references("NameService"); • NamingContext ncRef = NamingContextHelper.narrow(objRef); • // bind the Object Reference in Naming • NameComponent nc = new NameComponent("Hello", ""); • NameComponent path[] = {nc}; • ncRef.rebind(path, helloRef); • // wait for invocations from clients • java.lang.Object sync = new java.lang.Object(); • synchronized (sync) {sync.wait();} …}

11. public class helloClient { • 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"); • NamingContext ncRef = NamingContextHelper.narrow(objRef); • // resolve the Object Reference in Naming • NameComponent nc = new NameComponent("Hello", ""); • NameComponent path[] = {nc}; • hello helloRef = helloHelper.narrow(ncRef.resolve(path)); • // call the hello server object and print results • String hello = helloRef.sayHello(); • System.out.println(hello); • … }