EJB Concerns and AOP

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EJB Concerns and AOP

• by
• Neeraj Sangal

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Motivation

• Learn Aspect Oriented Programming and see how it
  can be applied to current problems

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Aspect Oriented Programming

• Language mechanisms to deal with cross cutting
  concerns
• The hard question for me which concerns are
  best expressed as aspects

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Java assert facility

• assert boolean-condition
• Language mechanism uses assert keyword
• Verify integrity of program structures
• Test pre and post conditions to methods
• AOP helpful in many cases not all

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EJB Model

• Component architecture for web based applications

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Types of EJBs

• Session
• Stateless/Stateful
• Entity
• Bean Managed/Container Managed
• Message Based

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AOP and EJBs

• Two approaches to think about
• How can the EJB operating environment benefit
  from AOP?
• How can EJB implementers benefit from AOP?
• This talk will examine the first approach
• This talk wont answer either question (sorry!)

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Using EJBs

• Client View
• Component View

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EJB Concerns

• Database connection pooling
• Persistence automatic and programmer controlled
• Transaction management
• Security
• Management of multiple instances of multiple
  components

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Working Set Management

• Callback methods
• ejbActivate()
• ejbPassivate()
• Serializes current state using standard java
  methods

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Security

• Define roles
• Define which roles are allowed to access an ejbs
  methods
• What is the best way to implement this?

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Container Managed Transactions

• The bean developer does not have to worry about
  transactions (is it true?)
• Callbacks
• afterBegin()
• beforeCompletion()
• afterCompletion()

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EntityBean

• Each entity bean represents a row of data in a
  table
• Two types
• Bean Managed Persistence
• Container Managed Persistence

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Home Interface Methods

• Create Methods
• Find Methods

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Managing Bean Instances

• Callbacks
• ejbActivate()
• ejbPassivate()
• ejbLoad()
• ejbStore()

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Deployment Descriptor

• Deployers responsibility relatively
  independent of Bean Developer
• Based on XML
• Example of method permission