Not another line of code for Servlets, JSPs, or EJBs should be written by anyone who hasn't read this book and understood the concepts explained. This book is about best practices in designing and coding J2EE applications. The lessons explained here were developed by the Sun Java Center based on their work in the field. As they developed applications for clients they noticed that the same problems occurred over and over again. This book documents the standard solutions to solve these problems that were built as a catalog of design patterns and best practices.
Part 1 is an introduction to design patterns and the J2EE platform. Part 2 is a catalog of bad practices (the authors describe these as, "less than optimal ways to solve problems"), and refactorings (ways to correct these problems). Developers working with poorly designed J2EE applications will find this section especially helpful.
In Part 3, fifteen separate design patterns and strategies are explained. Each pattern is described in detail with the motivation for using the pattern and the design goals to be achieved. UML class and sequence diagrams are included along with detailed code examples that serve to further clarify the pattern. These patterns aren't theoretical constructs but rather are practical strategies that can be applied to real world applications. Using the strategies in this book will make you more productive and your code easier to understand and maintain.
Anyone designing, architecting, or coding with J2EE will find this book to be extremely useful.