1. Enterprise Java Bean Technology Briefing Markus Hebach

2. Agenda sThe Need for a Server Side Component Model sEJB 1.0 Architecture Overview sWhere does CORBA fit in? sThe Inprise EJB Solution - “Kodiak”

3. The Need for a Server Side Component Model

4. Distributed TX’s Security Authorization Data Access Legacy Integration Developing a Distributed Object Business Logic

5. Business Logic Developer = After Tax Operating Cash Flow P/E Ratio CF = (R - O)(1 - T) + Dep(T) - NWC Net Present Value Holding Period Returns Salil “Number Crunch” Deshpande

6. System Developer = Distributed Transactions Persistence Authentication Authorization Concurrency Geoff “Codermaniac” Bullen

7. Productive Distributed Developer??? Business Logic Security Distributed TX’s Data Access Legacy Integration Authorization =

8. EJB Acknowledges “Roles” Bean Provider Assembler DeployerSys Admin Logic Developer No Transaction Code No Concurrency Code No Security Code No Distribution of Beans Composes Applications Generally Understands Logic Expert at Apps, Applets Servlets etc.. Usually builds GUI Deployment to Operational Environment Defines Security Roles Defines Transactions A Systems Expert System Manager Keeps System Operational Typically a good card player

9. The EJB Development Flow JBuilder EJB JBuilder Servlet HTML JSP EJB Server EJB EJB Server EJB HTML JSP Servlet

10. EJB Architecture & Roles EJB Server Client App EJB Container EJB Bean Provider EJB Server Provider Assembler Deployer System Admin

11. EJB Architecture Overview

12. Enterprise Java Beans “The Enterprise Java Beans Architecture is a component architecture for the development and deployment of object oriented distributed enterprise-level applications”. - Sun Microsystems EJB 1.0 Specification March 1998

13. Responsibilities of the Container  Proper creation, initialization, and removal of beans  Ensuring that methods run in the proper transaction context  Visibility of the home object in a JNDI-accessible namespace  Swapping to and from secondary storage (for session beans)  Persistence management (for container managed entity beans)  Availability of a home object implementing creation and lookup services  Implementation of certain basic security services

14. Identifying an EJB EJB (ejb-jar) EJB Home EJB Remote Bean Instance Deployment Descriptor

15. Bean Architecture EJB Home Bean Instance RemoteInterface Container

16. EJB Home The Home Interface contains the signatures of the creation methods for the given bean. Each Create method must have a corresponding ejbCreate method in the bean. Remember - Only the container can actually create the instances! public interface myHome extends EJBHome { public myObject create() throws RemoteException; public myObject create(String str) throws RemoteException; }

17. EJB Remote In a similar fashion, the developer must create a “Remote Interface” which describes the business methods (signatures) of the bean that the developer would like the client to have access to. public interface Account extends javax.ejb.EJBObject { public void deposit(double amount) throws RemoteException; public void withdraw(double amount)throws RemoteException; public double balance() throws RemoteException; }

18. EJB Object The methods in your bean will NEVER be invoked directly from the client. The client calls the bean’s methods indirectly through the EJBObject, which acts as a proxy. public interface javax.ejb.EJBObject extends java.rmi.Remote { public EJBHome getEJBHome() throws RemoteException; public Object getPrimaryKey() throws RemoteException; public Handle getHandle() throws RemoteException; public void remove() throws RemoteException, public boolean isIdentical(EJBObject other) throws RemoteException; }

19. Bean Types s Session Beans (Required for EJB 1.0) s Entity Beans (Optional for EJB 1.0) Types differentiated by Interface implemented and by the type declaration in the deployment descriptor.

20. Bean Types s Session Beans Execute on behalf of single client Can be transaction aware Does not represent directly shared data in a database Are relatively short lived Are removed when the EJB server crashes

21. Bean Types s Entity Beans Represents data in a database Are transactional Allows shared access by multiple users Survives crash of EJB server

22. Session Bean Types Stateless Session The bean does not contain conversational state between method invocations - as a consequence any session bean instance can be used for any client. Stateless beans are designed to be pooled.

23. Session Bean Types Stateful Session The bean contains conversational state which is kept across method invocations and transactions. Once a client has obtained a specific session bean it must use this instance for the life of the session.

24. EJB Server Clients View of Session Bean EJB Container Thin Client Windows Client Java Client Browser Client Mobile Client Cart CartHome CartBean JNDI CartHome cartHome = javax.rmi.Portable RemoteObject.narrow( initialContext.lookup(...), CartHome.class); Cart cart = cartHome.create(…); cart.addItem(66); cart.addItem(22);cart.purchase()cart.remove()

25. Entity Bean Types Bean Managed Persistence The entity bean implementation is responsible for implementing persistence. The bean provider writes the code to access the underlying database or application. These calls are placed in the methods ejbCreate(), ejbFind(), ejbRemove(), ejbLoad() and ejbStore().

26. Entity Bean Types Container Managed Persistence The container is responsible for implementing the persistence. Instead of the bean provider implementing the database access code, the container is responsible for generating the appropriate code and its execution. The fields of the entity bean, which are managed by the container are specified in the deployment descriptor.

27. EJB Server DB Session Bean Interacting with Entity Bean EJB Container Thin Client Windows Client Java Client Browser Client Mobile Client Cart CartBean JNDI OrderHome Order OrderBean order.findByPrimaryKey(orderNo); SQL ejbLoad(); placeOrder(); orderComplete(); ejbStore();

28. The Session Bean Interface package javax.ejb; public interface SessionBean extends EnterpriseBean { void setSessionContext (SessionContext s) throws RemoteException; void ejbRemove () throws RemoteException; void ejbActivate () throws RemoteException; void ejbPassivate () throws RemoteException; }

29. package javax.ejb; public interface EntityBean extends EnterpriseBean { void setEntityContext (EntityContext e) throws RemoteException; void unsetEntityContext () throws RemoteException; void ejbRemove () throws RemoteException; void ejbActivate () throws RemoteException; void ejbPassivate () throws RemoteException; void ejbLoad () throws RemoteException; void ejbStore () throws RemoteException; } The Entity Bean Interface

30. Holes in the EJB 1.0 Specification s No definition of Interoperability between containers. s Does not prescribe which RMI implementation should be used. s No definition for propagating Transaction Contexts s No recommendations for bridging security domains s No standard Container API

31. Where does CORBA fit in?

32. The role of CORBA in EJB “The Enterprise Java Beans Architecture will be compatible with CORBA. - EJB 1.0 Specification Section 2.1 Overall Goals

33. EJB 1.0 Section 4.4 Standard CORBA Mapping “To ensure interoperability for multi-vendor environments, we define a standard mapping of the Enterprise JavaBean client’s view contract to CORBA.” The mapping to CORBA covers: 1. Mapping of the EJB Client interfaces to CORBA IDL 2. Propagation of transaction context 3. Propagation of security context

34. Results of the CORBA Mapping s On the wire interoperability between EJB Servers from multiple vendors. s Enables non-Java clients to access EJB’s. s CORBA Object Services allow security and transactions to be handled in a distributed vendor independent manner.

35. “Open” implementation choices s RMI/IIOP s JNDI over COSNaming and/or LDAP s JTS/COSTransactions and IIOP s X.509 certificates/IIOP over SSL

36. The Inprise EJB Solution “Kodiak”

37. Inprise EJB Infrastructure Language Independent Client ATMSessionBean Java DB JTS 2 Phase Commit JNDINamingContainer AcctEntityBean Database RMI/ IIOP CosNaming LDAP CosTransactions Distributed 2 Phase Commit CORBA 2.3 Objects By Value Can generate IDL from the Home and Remote Interfaces. IIOP/SSL Access Control Complete Java Database

38. Inprise EJB Server Operation Modes sDevelopment Mode All services will run together in a single process JNDI/Lightweight Naming Service Lightweight JTS Implementation All Java Database for Container Managed Persistence sOperations Mode Fully Distributed Service JNDI/COSNaming ITS/COSTransaction implementation

39. A Fully Distributed EJB Solution Container Container JNDINaming Storage JTS/ITS JTS/ITS Distributed Transactions Distributed Security Domains Language Interoperability

40. EJB Server Competitors BEA WebLogic Tengah Bluestone Sapphire/Web GemStone GemStone/J IBM WebSphere Advanced Edition Novera jBusiness Oracle8i Oracle Application Server Persistence PowerTier Progress Apptivity