Design Pattern

widest range of applications development in the enterprise and distributed environments. Infact, the JEE modules and environment is still growing with a rapid pace. So, it is important to take advantage of the most efficient and effective strategies while re-factoring the existing projects and developing newer ones. These efficient and effective strategies in JEE scenario are known as the JEE-specific Design patterns.

JEE-specific design patterns identify the minimal set of known problems that application architecture should solve. These patterns are based on the experiences of the JEE community (involved with JEE development) to solve the problems.

Classification of JEE Design Patterns:

1. Business Tier Patterns
These business tier patterns tackle problems occurring in an application resulting from the presentation tier accessing distributed business services, network performances degradation due to multiple calls between client and server, memory impact due to retrieval of a large list of data, and so on. The patterns demonstrated here focus on and solve design problems occurring in the middle tier of a J2EE application.

• Session Facade Design Pattern
• Service Locator Design Pattern
• Value List Handler Pattern

2. Presentation Tier Patterns

The presentation tier patterns deal with the common problems occurring in the presentation layer such as - view management and navigation, processing of dynamic business data, efficiently accessing the read-only data, and so on. The patterns under this category focus on and solve design problems occurring in the presentation tier of a J2EE application for example:

Fast Lane Reader Pattern

3. Data Access Tier Patterns:

These data access tier patterns tackles best practices for an application accessing the database or the underlying persistence layer from the business tier. The patterns demonstrated


here focus on and solve design problems occurring in the data tier of a J2EE application.
Data Access Object Design Pattern

A word of CAUTION:

Patterns are not a magical stuff for a problem identified and a pattern applied does not mean that you will have a perfect solution, for that scenario. Patterns are just a way to introduce clarity into your system architecture. Patterns allow the possibility of building a better system meeting the intended business requirements, performing well, is maintainable, and is delivered on time. Above
all it keeps us engineering in business…..

Few of the familiar Design Patterns in Java

1 Interface

Objects define their interaction with the outside world through the methods that they expose. These methods form the object’s interface with the outside world, for example, the buttons on the front of your television set, are the interface between you and the encapsulated electrical television components.

An interface pattern encapsulates a coherent set of services and attributes, without explicitly binding the functionality to a particular object or a code. In Java an interface is a programming construct, similar to an abstract class, that allows you to specify zero or more method signatures without providing the implementations of those methods. Implementing an interface allows a class to become more formal about the behavior it promises to provide. Interfaces form a contract between the class and the outside world, and this contract is enforced at build time by the compiler. If your class claims to implement an interface, all methods defined by that interface must appear in its source code before the class will successfully compile.

2 Abstract
Abstract pattern can be used to create an abstract class

July 2007 | Java Jazz Up |29
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