Case Study: Developing Enterprise Applications using J2EE Design Patterns

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E137Case Study Developing Enterprise
Applications using J2EE Design Patterns

• Raghu Premkumar
• Senior Systems Analyst
• Option One Mortgage Corporation
• Rpremkumar_at_oomc.com
• Jim Kawanami
• Sybase, Inc.
• Jim.Kawanami_at_Sybase.com

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Outline

• What is a Pattern?
• Objective
• Design
• Interactive Demo and Code
• Issues
• Related J2EE Patterns
• QA

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What is a Pattern?

• From Core J2EE Patterns Best Practices and
  Design Strategies (Alur, Crupi, and Malks)
• Patterns are about communicating problems and
  solutions.
• patterns enable us to document a known recurring
  problem and its solution in a particular context,
  and to communicate this knowledge to others.
• the goal of the pattern is to foster conceptual
  reuse over time.

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What is a Pattern?

• Architectural Patterns vs. Design Patterns
• Architectural Pattern example
• Model-View-Controller
• Design Pattern examples
• Service Locator, Front Controller, Observer

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MVC Architectural Pattern (Applied)
Another EJB
Request
Front Component
Session Bean
Jaguar NVO
Java Bean
HTML
JSP
View Components
Tag Library
EJB and Component Tier
Web Tier
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Objective

• Provide an efficient, generalized means to
  support EJB lookup and creation accessible by
  different client types.
• Use a Service Locator object to abstract all
  JNDI usage and to hide the complexities of
  initial context creation, EJB home object lookup,
  and EJB object re-creation. Multiple clients can
  reuse the Service Locator object to reduce code
  complexity, provide a single point of control,
  and improve performance by providing a caching
  facility.
• - Core J2EE Patterns

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Design

• The Service Locator pattern may be readily
  extended
• Key features in our implementation include
• Reflection
• Collection to store EJB references
• ???

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Interactive Demo and Code
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Issues

• Issues encountered in implementing our Service
  Locator
• Some points to consider in designing your Service
  Locator classes
• Missing EJB reference in collection
• EJB handle in use
• Recycling handles

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Related J2EE Patterns

• Other relevant and related Design Patterns
• These patterns should also be considered in the
  application architecture to create the completed
  design
• Observer
• Session Facade
• Strategy

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QA
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