Introduction to EJB INFORMATICS ENGINEERING – UNIVERSITY OF BRAWIJAYA Eriq Muhammad Adams J

Agenda  What is EJB ?  EJB3 Simplified Development Model  Distributed Computing Model  The EJB Component Model  Core Features of EJB  Application Server  Typical EJB 3 Application Architecture  How to use EJB within Glassfish ?

What is EJB 3?  EJB 3 defined by JSR 220  History  EJB 1.0 EJB 1.1 EJB 2.0 EJB 2.1 EJB 3  EJB 3 Simplified Development Model  Distributed Computing Model

EJB3 Simplified Development Model  XML and Annotations – free to choose between XML configuration or annotation.  Dependency Injection – inject dependency at runtime with annotation or XML.  Interceptors: Callback Method – support aspect oriented programming  POJO Implementation.  Intellegent use of defaults – configure explicitly when we need non-default configuration.

Distributed Computing Model  EJB Roles – we can give privelleges.  Enterprise Bean Provider – responsible for defining and implementing the business logic and structure of an enterprise bean.  The Application Assembler - combines EJBs into EJB modules and entities into persistence archives, and then combines these modules together with other Java EE modules to produce an application.  The Deployer – deploys it to a particular EJB container.

The EJB Component Model  We build three object types :  Session Beans perform business service operations and orchestrate transaction and access control behavior.  Message Driven Beans (MDBs) invoked asynchronously in response to external events, through association with a messaging queue or topic.  Entities objects that have unique identities and represent persistent business data.

Core Features of EJB 3  Declarative Metadata - annotations vs XML  Configuration by Exception - implicit default configuration  Scalability - pooling, cache, optimistic locking strategy, avoid concurrency locking  Transactionality - distributed transactions  Multiuser Security - declarative method access control  Portability - deployable to any application servers  Reusability - loosely coupled components  Persistence - POJO

Application Server  Is a EJB container.  Host EJB Module or application.  Real implementation of EJB provide by application server.  Many open-source or propietary application server available for market, such as IBM Websphere, Oracle Application Server, BEA Weblogic, Oracle Glassfish.  We used Oracle Glassfish v3 in this class.

Typical EJB 3 Application Architecture EJB Container or JEE Application Server Database Desktop Client Web Server Mobile Client Web Browser

References  EJB In Action, Manning  Beginning EJB 3 Application Development, Apress