Developing with POJOs: faster and easier - POJOs in Action: Developing Enterprise Applications with Lightweight Frameworks - page 14

Table 1.1 Comparing classic EJB and POJO approaches (continued)

Classic EJB approach POJO approach

Transaction management EJB container-managed

transactions

Spring framework

Application assembly Explicit JNDI lookups Dependency injection

Don't worry if you are not familiar with all of these terms. In this section, I'll
examine each difference and explain and justify the POJO approach. You will see
how to develop business logic using the POJO approach. I use the money transfer
application from section 1.1.2 as an example.

1.2.1 Using an object-oriented design

Rather than structuring the money transfer example around methods such as
transfer() and its helper methods, the code should be structured around an
object model, which is a collection of classes that typically corresponds to real-
world concepts. For example, in the money transfer application, the object model
consists of classes such as Account , OverdraftPolicy , and BankingTransaction . In
addition, there is a TransferService that coordinates the transfer of money from
one account to another. Figure 1.2 shows the design.

TransferService

BankingTransaction transfer(fromId, toId, amount)

Banking
Transaction

Account

<<interface>>
OverdraftPolicy date

balance

allow(Account, amount)

debit(amount)
credit(amount)

Transfer
Transaction

from

NoOverdraft
Policy

Limited
Overdraft

amount

to

Figure 1.2 An object model for the money transfer application