The Preferred Characteristics of an Object-Oriented Architecture

Introduction

Building complex, well-behaved, object-oriented software is a difficult task for several reasons. First, simply programming in Java does not automatically make your application object-oriented. Second, the process by which you become proficient at object-oriented design and programming is characterized by experience. It takes a lot of time to learn the lessons of bad software architecture design and apply those lessons learned to create good object-oriented architectures.

The objective of this chapter is to help you jump-start your object-oriented architectural design efforts. I begin with a discussion of the preferred characteristics of a well-designed object-oriented architecture. I then present and discuss three important object-oriented design principles that you can immediately apply to your software architecture designs to drastically improve performance, reliability, and maintainability.

The three design principles include the Liskov Substitution Principle (LSP), the Open-Closed Principle (OCP), and the Dependency Inversion Principle (DIP). Bertrand Meyer’s Design by Contract (DbC) programming is discussed in the context of its close relationship to, and extension of, the Liskov Substitution Principle.

An understanding of these three design principles, coupled with an understanding of how to apply them using the Java programming language, will significantly improve you ability to design robust, object-oriented software architectures.