Chapter 4: Design Techniques and Coding Standards for J2EE Projects

Overview

As J2EE applications tend to be large and complex, it's vital that we follow sound OO design practice, adopt consistent coding conventions, and leverage existing investment – whether our own or that of third parties. In this chapter we'll look at each of these important areas in turn.

The first two concern code quality, at object-design and code level. What are we trying to achieve? What is good code? These are a few of its characteristics:

• Good code is extensible without drastic modification. It's easy to add features without tearing it apart.

• Good code is easy to read and maintain.

• Good code is well documented.

• Good code makes it hard to write bad code around it. For example, objects expose clean, easy-to-use interfaces that promote good use. Both good code and bad code breed.

• Good code is easy to test.

• Good code is easy to debug. Remember that even if a piece of code works perfectly, it's still a problem if it doesn't favor debugging. What if a developer is trying to track down an error in imperfect code, and the stack trace disappears into perfect but obscure code?

• Good code contains no code duplication.

• Good code gets reused.

It's hard to write code that achieves these goals, although Java arguably gives us more help than any other popular language.

I've written and debugged a lot of Java code since I started using the language back in 1996 (and plenty of C and C++ before that) and I'm still learning. I don't pretend that this chapter contains all the answers, and there are many matters of opinion, but hopefully it will provide some guidance and useful food for thought. This is an important area.

We must not only ensure that we write code right, but also that we write the right code, taking advantage of existing solutions wherever appropriate. This means that development teams must work closely to avoid duplication of effort, and that architects and lead developers must maintain up-to-date knowledge of third-party solutions such as open source projects.

This chapter, like this book, is focused on J2EE 1.3, and hence J2SE 1.3. However, language and API improvements in J2SE 1.4 are discussed where relevant, as J2SE 1.4 is already available and can even be used with some J2EE 1.3 application servers.