Developing with POJOs: faster and easier - POJOs in Action: Developing Enterprise Applications with Lightweight Frameworks - page 13

increase developer productivity. i BATIS is also layered on top of JDBC , but it maps
POJO s to SQL statements and is a very convenient way to execute SQL statements.
The Spring framework has a wide range of features that make it easier to use than
EJB , including the equivalent of container-managed transactions for POJO s.
An important feature of these technologies is that they are nonintrusive.
Unlike EJB s, they provide transactions and persistence without requiring the
application classes to implement any special interfaces. Even when your applica-
tion's classes are transactional or persistent, they are still POJO s, which means that
you continue to experience the benefits of POJO s that I describe in this chapter.
Some excellent topics are available that describe these frameworks in depth:
Hibernate in Action [Bauer 2005], Spring in Action [Walls 2005], i BATIS in Action
[Begin, forthcoming], and Java Data Objects [Russell 2003]. You do not need to
read these topics to understand and benefit from this topic. But to apply what you
learn here you do need to read them to learn the details.
In this section I will provide an overview of how to use POJO s and lightweight
frameworks to redesign the money transfer service and make it easier to develop,
test, and maintain. This new design is object-oriented POJO -based instead of a
procedural EJB -based. It accesses the database using a persistence framework that
is layered on top of JDBC instead of using JDBC directly. The business logic is
encapsulated by a POJO façade instead of a session bean, and transactions are
managed by the Spring framework instead of the EJB container. The business
logic returns real business objects to the presentation tier instead of DTO s. The
application is assembled by passing a component's dependencies as setter or con-
structor arguments instead of the component using Java Naming and Directory
Interface ( JNDI) lookups. Because the design is object-oriented and uses these
lightweight technologies, it is much more developer-friendly than the EJB version
we saw earlier.
Table 1.1 summarizes the differences between the two designs.

Table 1.1 Comparing classic EJB and POJO approaches

Classic EJB approach POJO approach

Organization Procedural-style business logic Object-oriented design

Implementation EJB-based POJOs

Database access JDBC/SQL or Entity beans Persistence framework

Returning data to the
presentation tier

DTOs Business objects