Developing with POJOs: faster and easier - POJOs in Action: Developing Enterprise Applications with Lightweight Frameworks - page 29

Spring TransactionInterceptor

<<interface>>
TransferFacade

TransferResult transfer(fromId, toId, amount)

TransferFacadeImpl

TransferResult transfer(fromId, toId, amount)

TransferService

TransferResult

BankingTransaction transfer(fromId, toId, amount)

Account <<interface>>

BankingTransaction
Repository

<<interface>>
Account
Repository

Banking
Transaction debit(amount)

credit(amount)

createTransaction(... )

findAccount(id)

<<interface>>
OverdraftPolicy

HibernateBanking
Transaction
Repository

Hibernate
Account
Repository

findAccount(id) createTransaction(... )

NoOverdraft
Policy

Limited
Overdraft

Hibernate

Figure 1.8 Money transfer service implemented with POJOs, Hibernate, and Spring

I have omitted some of the details, but I hope you can see what you can accomplish
with POJO s and lightweight frameworks such as Spring. By using Spring, we have
the functionality we formerly needed from the EJB container. By using POJO s, we
also have a design and structure of code that is impossible if we use the heavyweight
J2EE application server and all its services. Using the lighter weight tools allows us
to improve the structure, maintainability, and testability of our code.