Enterprise Java Beans

Summary

• N Tier Applications
  • Structuring N Tier Applications
    • Design Alternative: Coarse Grain Session Beans
    • Design Alternative: Data Access Object
    • Design Alternative: Session Bean with Entity Bean

N Tier Applications

• Persistence
• Transactions
• Caching
• Clustering
• Security

Structuring N Tier Applications

• Web Server
  • Client Container
  • Applet Container
• Presentation Logic
  • Web Container
• Business Logic
  • EJB Container

Beans:

• Bundle of Java Objects
  • Unit of Reuse
    • Entity
      • Row of a database
      • Persistence may be built into entity or into container
    • Session
      • Associated with particular client (and temporal window)
      • Stateful or Stateless
    • Message
      • Async behavior
      • Data sent between entities

Design Alternative: Coarse Grain Session Beans

Design Alternative: Data Access Object

DAO using entity bean -> Container Managed Persistence, Bean Managed Persistence

Pro:

• Concurrency

Con:

• Business Logic Exposed

Design Alternative: Session Bean with Entity Bean

Pros:

• Business logic not exposed
• Concurrency