Java 2 Enterprise Edition

1. Java 2 Enterprise Edition An Introduction

2. Agenda • What is J2EE? • Evolution of Distributed Transactional Computing • Why J2EE? • J2EE • Deliverables (what and why?) • Basic Architecture • Components and Containers • Roles • Lifecycle (c)CDAC(Formerly NCST)

3. Overview • A collection of enterprise technologies • Provides a component based approach to the design, development, assembly and deployment of enterprise applications • An open industry standard (initiative led by Sun Microsystems) J2EE enables solutions for developing, deploying and managing n-tier sever-centric enterprise applications (c)CDAC(Formerly NCST)

4. Mission • To provide a platform-independent, portable, multiuser, secure, and standard enterprise-class platform for server side deployments written in the Java Language • Implement a standardized execution environment for distributed enterprise applications (c)CDAC(Formerly NCST)

5. Evolution of Distributed Transactional Computing • Overview of technologies leading to distributed computing • 1 tier, 2 tier, 3 tier, n tier architecture • Distributed objects • Application Servers (c)CDAC(Formerly NCST)

6. Single tier application • Data access, presentation and business logic, all tightly coupled in one monolithic application Dumb terminal Main frames (c)CDAC(Formerly NCST)

7. Client/Server architecture[2-tier] • Presentation, business and data model processing logic into client application • Server is typically a database server • Client sends SQL statements, retrevies raw data Database Server Database Specific APIs Workstation (c)CDAC(Formerly NCST)

8. Client/Server architecture[2-tier] • Fat Clients • Data model tighly coupled with each client ( a change in schema will require making changes in every client ) • Clients use database APIs for communication/transactions etc. • All processing at the client end • Issues – Scalability, Performance, Security, Reuse, Maintenance (c)CDAC(Formerly NCST)

9. Three-tier architecture • Thin clients, business logic moves to middle tier • Separates UI, business logic and data model • Middle tier serves the business logic as “Services” • Explict management of multi-threading, concurrency, transactions, security etc. required RPC Database Server Database Specific APIs calls RPC (c)CDAC(Formerly NCST)

10. Distributed Object architecture [3-tier] • Business logic and data model as distributed objects (solutions available from Java RMI-IIOP, CORBA, Microsoft .NET) • Uses object request protocols – IIOP, RMI, DCOM/COM+ • Middle tier handles – concurrency, multi-threading, connection pooling etc. • Still, can be difficult to program Database Server Database Specific APIs calls IIOP, RMI, DCOM Distributed Objects (c)CDAC(Formerly NCST)

11. Adding Web tier [N-tier] • Distributed computing became ubiquitous with Web-interfaces/clients • CGI/Perl – difficult to maintain, scalability issue • A mixture of different technologies, difficult to maintain/manage • Proprietary solutions limit exploration Database Server JSP/Servlets, ASP, CGI IIOP, RMI, COM, DCOM Web Server Application Server (c)CDAC(Formerly NCST)

12. Moving from 1-tier to n-tier • Distinct separation of responsibilities • Change in a specific tier possible without disturbing other tiers - easier maintenance, deployment • Reusable, flexible, scaleable • However, • Requires developer to worry details of distributed protocol, security, load balancing, concurrency, transactions, resource management … (c)CDAC(Formerly NCST)

13. N-tier J2EE Architecture EJB Application Server RMI-IIOP Container Application Client Database Server (RBDMS) HTTP (JSP/Servlets) Web Server Web-Client Legacy Systems (c)CDAC(Formerly NCST)

14. The Java 2 Platform Hand-held devices High-end Servers Workgroup Servers Desktop Micro Edition (J2ME) Enterprise Edition (J2EE) Standard Edition (J2SE) (c)CDAC(Formerly NCST)

15. J2EE Bundle • APIs and technology specification • A collection / integration of various enterprise APIs • Development and Deployment platform • A unified platform for server-side development • Reference Implementation • Implements the J2EE specification & demonstrates its viability • Compatibility tests • Certifies a J2EE product, confirms application portability • J2EE Blueprints • Programming model, patterns, guidelines, best practices (c)CDAC(Formerly NCST)

16. J2EE Technologies • Component Technology • Applet, application clients, Enterprise beans, web components (JSP / Servlets) • Service Technology • JDBC, JNDI, JTS, Connector Architecture, Web Services etc • Communication Technology • RMI-IIOP • Internet protocols (HTTP, SSL, TCP/IP) • Messaging (JMS, JavaMail) (c)CDAC(Formerly NCST)

17. J2EE APIs (Bundled) • Java 2 SDK • Java Standard APIs (part of J2SE) • Enterprise JavaBeans (EJB) • Aritecture for building server-side components • Java Remote Method Invocation (RMI) & RMI-IIOP • Method invocation across Java virtual machines. Can also integrate with other clients comfirming CORBA IIOP specification • Java Naming and Directory Interface (JNDI) • Naming service for locating resources over the network • Java Database Connectivity (JDBC) • Java interface to relational database • Java Servlets & Java Server Pages (JSP) • Technology allowing dymanic web content generation • Java Activation Framework (JAF) • J2EE Connector Architecture (c)CDAC(Formerly NCST)

18. J2EE APIs (Bundled) contd … • Java Messaging Service (JMS) • Enables asyncronous communication, including point-to-point and publish/subscribe messing • Java IDL • Java technology based CORBA ORB implementing a subset of CORBA specification • JavaMail • Mailing APIs • Java API for XML Parsing (JAXP) • XML parsing and manipulation. Used to describe EJB components, file scripts • Java Transaction API (JTA) and Java Transaction Service (JTS) • Used to manage transactions • Java Authentication and Authorization Service (JAAS) • Security services API • Others (performance specific, not mandated by the specification) • Load balancing, data caching, transparent failover, etc (c)CDAC(Formerly NCST)

19. Basic Architecture (c)CDAC(Formerly NCST)

20. Application Deployment Architecture (c)CDAC(Formerly NCST)

21. Application Model • Three fundamental parts • Components • Captures the business process & data model • Containers • Intercede between clients and components and provides services like resource pooling, transaction support, etc • Defines component behaviours for clients • Hides low-level system functionalities • Connectors • Provides plug-in support for application portability (c)CDAC(Formerly NCST)

22. J2EE Components • The J2EE platform uses a multitiered distributed application model • The J2EE application components parts comprise: • Client-tier components (run on the client machine). • Web-tier components (run on the J2EE server). • Business-tier components (run on the J2EE server). • Enterprise information system (EIS)-tier software (runs on the EIS server). • Essentially considered to be three-tiered application, because of being distributed over client, J2EE server and the database. (c)CDAC(Formerly NCST)

23. J2EE Components: Client Tier • Client • Web clients (web-browser, web pages, applets –) • Application client (application user interface built using Swing or AWT, or a command line interface) • CORBA IIOP complaint clients (c)CDAC(Formerly NCST)

24. J2EE Components: Web-tier • Web components • Servlets or JSP pages • JavaBeans (optional) (c)CDAC(Formerly NCST)

25. J2EE Components: Business tier • Business Components • Enterprise Beans handle the application logic • Separates business process (session beans) and data component (entity beans) • Applications requiring messaging facility use JMS (c)CDAC(Formerly NCST)

26. J2EE Components: Data tier • Application Database Server • Any relational database (eg Oracle, MS SQL, etc) • Enterprise Information System (EIS) • Includes enterprise systems like ERP, mainframe transaction processing, database systems and other legacy information systems • J2EE applications often rely on this tier to store the enterprise’s business critical data (c)CDAC(Formerly NCST)

27. Container Services • Security • Transaction Management • Naming and directory • Remote connectivity • Lifecycle management • Persistance • Concurrency (c)CDAC(Formerly NCST)

28. Container Types • The deployment process installs J2EE application components in the J2EE containers • EJB container • Web container • Application client container / Applet container • The J2EE server provides EJB and Web containers and is the operating run-time environment (c)CDAC(Formerly NCST)

29. Client J2EE Server and Containers J2EE Server Web Container Servlet JSP Page Web Browser Database Application Client Container Application Client EJB Container Enterprise Bean Enterprise Bean (c)CDAC(Formerly NCST)

30. J2EE Roles • J2EE product provider • One who designs and makes available the J2EE platform, APIs and other features defined in the J2EE specification • Component Provider • One who provides web components, enterprise beans, applets or application clients for use in J2EE applications. • Application Assembler • One who gets the components and assembles it into an application (c)CDAC(Formerly NCST)

31. J2EE Roles • Application Deployer and Administrator • One who configures and deploys the J2EE application, administers and monitors the deployment • Tool provider • One who creates development, assembly and packaging tools used by component providers, assemblers and deployers (c)CDAC(Formerly NCST)

32. J2EE Lifecycle (c)CDAC(Formerly NCST)

33. References • J2EE Tutorial, Sun Microsystems • Simplified guide to the Java 2 Platform, Enterprise Edition, Sun Microsystems • Sun TechDays Conference 2000-2001 slides, • Sun Microsystems • Mastering Enterprise JavaBeans, 1st & 2nd Edition • By Ed Roman (c)CDAC(Formerly NCST)