CS401

Session Facade Pattern

Bank example invoked from a Servlet directly to Database (entity beans)

Problems:

Too many network requests (Client to database)....6
Not scalable as increase number of clients (tie up resources..database) while servicing client needs
If not carefull, the logic could do the withdrawl and fail on the deposit and the money would be floating in the system

A Solution.....the Session FacadePattern

Now have 1 network request to a Session Facade code (BankTeller Session EJB)
Bundle all of the business logic in a seperated Session Facade code (Bank Teller Session EJB)
Able to have better control of processes ...not fail on deposit or put back money

Extensible to other Business Logic (Session Facade)

Synopsis: Session Facade

Name: Session Facade

Context

A client needs to execute business logic in order to complete a use case.

Problem (forces)

How can a client execute a use case's business logic in one transaction and one bulk network call?

Solution

Wrap any business logic in a layer of session programs called the Sesion Facade. Clients should only have access to these session programs (beans) and not any underlying data layers, etc. The session programs (beans) ideally sit on same network/machine as data programs (entity beans) thus reducing network load.

Related Patterns

Message Facade, Data Transfer Object.

AVOID:

Creating session facade "SUPER Class" ...Sometimes developers want to put all the use cases in a systemn in one session bean. This results in a bloated session bean and reduced development productivity.