What is a Pattern?
"Solution to recurring problem in a context"
Context : What is the environment like?
Problem: What do I want to do?
Solution: How do I do it?

Core J2EE patterns are platforms patterns
The context is bounded by the J2EE platform
* 21 Patterns are categorized by tiers
* Presentation tier
* Business tier
* Integration tier

Tiered Approach (Logical Architecture)
* Client Tier (Application clients, Applets, apps ) - User Interaction/Devices
* Presentation Tier (JSP, Servelts) -Single sign on, Session Mgt, Content creation, format and delivery.
* Business Tier (EJBs, Others Business Objects) - Business Logic, Transactions, data, services
* Integration Tier (JMS, JDBC, Connectors and Legacy) - Resource adapters, legacy, external systems, rules engine, workflow
* Resource Tier (Databases, external system and legacy) - Resources, data and external services

Core J2EE Design Patterns
Presentation Tier Patterns
* Intercepting Filter
* Front Controller
* View Helper
* Composite View
* Service to Worker
* Dispatcher View
* Context Object
* Application Controller

Business Tier Patterns
* Business Delegate
* Session Façade
* Service Locator
* Transfer Object
* Composite Entity
* Transfer Object Assembler
* Value List Handler
* Business Object
* Application Service

Integration Tier Patterns
* Data Access Object
* Service Activator
* Domain Store
* Web Service Broker

About Author / Additional Info:
Arivuvel Ramu
Technical Architect (SOA)