1. Alan L. Batongbacal CS 4244 / 01 Nov 2000
J2EE: A Bird’s-Eye View
Alan L. Batongbacal
CS 4244 / 01 Nov 2000

2. What is J2EE?
A set of Java-related software practices and technologies for building enterprise-class applications
Emphasis on availability, security, reliability and scalability
Multi-tiered application model

3. Why use multiple tiers?
Enterprises spread across multiple geographic and organization boundaries
Pendulum has swung from data center to desktop to somewhere in-between

4. Component Technologies
Enterprise JavaBeans
Java Servlets
Java Server Pages
HTTP / HTTPS
Java RMI-IIOP
JavaIDL
JDBC
Java Naming and Directory Interface
JavaMail and Java Activation Framework
Java Messaging Service
Java Transaction API

5. Enterprise JavaBeans Partition app construction task by role
Shift much of development burden to bean containers by taking advantage of container services
Select desired services declaratively
Support non-persistent (session) and persistent (entity) usage
Roles: bean provider, container provider, server provider, application assembler, deployer, system admin
Container services: distributed transaction management, security, resource management and component lifecycle, persistence, remote accessibility, multiclient support, component location transparency

6. EJB App Construction Roles
Bean provider
Container provider
Server provider
Application assembler
Application deployer
System administrator

7. EJB Container Services
Implicit: distributed transaction management, security, resource management and component lifecycle, persistence, remote accessibility, multiclient support, component location transparency
Explicit: naming and directory services

8. Java RMI-IIOP
Java RMI uses Java Remote Method Protocol (JRMP) as its default comm layer
Internet Inter-ORB Protocol (IIOP) is the standard protocol used by CORBA
Provides greater reusability, cross-language use, better integration into legacy systems, firewall navigation and context propagation

9. Java IDL
Addresses semantic differences between RMI and CORBA relating to distributed garbage collection, object conversion and type mapping

10. JDBC Provides access to most database management systems via SQL
Similar, though not identical to Microsoft ODBC

11. Java Naming and Directory Interface
Provides a unified API for associating names with objects, accessing objects by their names and associating attributes with objects
Acts as an adapter to LDAP, Novell NDS, Sun NFS, Java RMI and both Unix-style and DOS-style file systems

12. JavaMail and Java Activation Framework
Provides a high-level API for accessing an system
Uses service providers for SMTP, IMAP, POP3 and other protocols
JAF provides means to describe and display content of varying types

13. Java Messaging Service
Provides an API for message-based interprocess communications
Supports point-to-point and publish/subscribe models
J2EE provides interfaces; third-party vendors supply implementations (IBM MQSeries, Progress SonicMQ, FioranoMQ)

14. Java Transaction API
Low-level API for defining units of work and maintaining the logical integrity thereof
Not explicitly used by EJB programmers

15. EJB Container/Server Implementations
Reference implementation from Sun
BEA Systems WebLogic
IBM WebSphere
Oracle 8i
enhydra.org
openejb.org

16. Future Directions Updates to EJB, Servlet and JSP specs
Addition of JAXP, JAAS
Addition of message-driven bean type
Addition of J2EE Connector Architecture
Improvements to container-managed persistence

17. Other Technologies Common Object Request Broker Architecture (CORBA)
Microsoft COM/DCOM, COM+, .NET

18. Additional Reading
“Designing Enterprise Applications with the Java 2 Platform, Enterprise Edition”,
“Mastering EJB” by Roman (Wiley)
“Developing Java Enterprise Applications” by Asbury and Weiner (Wiley)
“Java Network Programming” by Harold (O’Reilly)