Newsletter sign-up
View all newsletters

Enterprise Java Newsletter
Stay up to date on the latest tutorials and Java community news posted on JavaWorld

Sponsored Links

Optimize with a SATA RAID Storage Solution
Range of capacities as low as $1250 per TB. Ideal if you currently rely on servers/disks/JBODs

JavaWorld.com > Java Development Tools >

E++: A pattern language for J2EE applications, Part 1

Build better J2EE applications with a high-level pattern language

By Bin Yang, JavaWorld.com, 04/20/01

  • Print
  • Feedback
.
Your company decides to build or migrate from existing two-tier applications to an n-tier J2EE solution. The targeted application needs to have characteristics of modularity, reusability, extensibility, portability, inversion of control, consistence, and scalability (MREPICS) (see the sidebar for more on MREPICS principles). Your task: efficiently build a high-quality application leveraging standard J2EE components.

Read the whole "E++: A Pattern Language for J2EE Applications" series:



Rather than design all the pieces from scratch, you wisely desire to leverage the well-established Gang of Four (GOF) design patterns. The challenge: you must select among two dozen GOF design patterns under a functional taxonomy (creational, structural, and so on) and apply them to J2EE components. Sound tough? In this article, you'll learn how to make the process easier with the E++ language.

E++ makes design patterns friendlier to designers by effectively coordinating patterns in real projects. Different from the GOF's taxonomic approach, the E++ pattern language contains not only design patterns, but also architectural patterns that provide frameworks of the whole application for design patterns. Moreover, it describes the rules for design patterns working together to construct a high-quality J2EE framework. In short, E++ shows how to architect a real-world J2EE project using closely related design patterns.

In the sections below, we will first establish the foundation of the language, then, beginning with the Layered Architecture pattern, describe the whys and how-tos of decomposing the system and partitioning functionalities in different subsystems. Next, the MVC architecture pattern provides a set of patterns for laying out the architecture of an interactive B2C scenario. Further, the REAI (Rule Engine-Based Enterprise Integration) architecture pattern depicts how the application integrates with backend remote systems. A few deployment patterns are also addressed to help deploy applications in production.

Pattern language: A better approach

The first systematic attempt to describe patterns was made by the ancient Greeks, resulting in Aristotelian prepositional logic. Indeed, the heart of today's Pentium processor comprises a complex of prepositional logic patterns, etched into silicon.

The current design pattern movement draws on the work of the architect Christopher Alexander. In A Pattern Language, he suggested that each design pattern, "... is a rule, which establishes a relationship between a context, a system of forces which arises in that context, and a configuration which allows these forces to resolve themselves in that context" (Christopher Alexander, 1977). In an object-oriented programming environment, a pattern indicates a cluster of cooperating objects linked by certain relationships found repeated in a design. Application design is tremendously hard work, and with design patterns existing in isolation and without correlation, it is always a struggle to integrate the patterns into an actual design project.

  • Print
  • Feedback

Resources