J2EE design decisions - POJOs in Action: Developing Enterprise Applications with Lightweight Frameworks - page 33

part of the lightweight approach whereas session beans and message-driven beans
are part of the heavyweight approach.
Choosing between the heavyweight approach and the POJO approach is one of
the first of myriad design decisions that you must make during development. It's a
decision that affects several aspects of the application, including business logic
organization and the database access mechanism. To help decide between the two
approaches, let's look at the architecture of a typical enterprise application, which
is shown in figure 2.1, and examine the kinds of decisions that must be made
when developing it.

Presentation Tier

How to
encapsulate the
business logic

How to organize
the business
logic

Business Tier Interface

Business Tier

How to handle
concurrency in
long-running
transactions

Persistence Tier

How to access
the database

Database

How to handle
concurrency in
short transactions

Design Decisions

Figure 2.1 A typical application architecture and the key business logic and database access
design decisions