Patterns of Enterprise Application Architecture (Hardcover)

So what is the problem? The title is misleading. It is about patterns, but not really about enterprise applications. I am not in the subject of enterprise applications. I never ever have touched a program like SAP or a language like COBOL. But I encountered nearly every problem addressed in the patterns. Even the money class has corresponding problems in other fields: a Voltage has both a value and a unit. Also having complaints about the fact that 3 times 33% are less than 100% are always common.

What is this book about? It is basically about problems you have in moderately big applications. How do you connect a relational database with its structure and transactionality to a system, especially an object-oriented system (but not only)? And how do you connect to the user interface, especially a web interface. Also it contains a lot of useful small patterns at the end. As you can see: a lot of valuable stuff for many people. Yes and you get the deep judgments and fine humor of Martin Fowler too.

What is the main problem? This book is not really suited for actual reading. It contains an introductory part of a hundred and a reference part of four hundred pages. The introduction part is annoying to read. It is at the same time too simple (Some knowledge of relational databases should be a requirement for this book, and much more...) and too difficult (An extremely lot of forward references to patterns described later in this book). Also a lot of stuff is in the most trivial sense repeated within a few pages distance only. And it is repeated down to the wording of the individual sentences.

The reference part is a lot better. It gets better to read the further along you already read. The number of forward references gets less along the way. I liked especially the last part about base patterns. As their name already says they should have been much more to the beginning of the book.

This book contains an excellent book within it, just waiting to be "refactored" out of this collection of valuable thoughts. I firmly believe that Martin Fowler is well suited to do this refactoring job. I do sincerely hope that he does it for the next edition of the book. Most of the work is already invested and the result would be very valuable for many people. It is possible to write excellent and readable books about patterns as for example Buschmann et al in "Pattern Oriented Software Architecture" showed.

One of the nice things about the book is how the code tends to de-emphasize the application container by doing most of the work in the raw database access systems (e.g. JDBC), which makes it easy to understand what is going on but will offend the true J2EE believer. This makes the patterns in the book accessible to anyone coding in any environment, which I greatly appreciate.

One pet peeve is that some of the patterns are obvious shells for a single technique, such as the Transform View, which is really just XSLT. The text says as much, but shouldn't there be more than one example of a particular pattern in nature? It's just a pet peeve though, it's no reason to avoid the book.

Overall, the book is well written and edited and the graphics add to the exposition but are not gratuitous. It's a useful guide for anyone looking to raise the level of the enterprise application (read web application) thought up to the next level.

The book is particularly strong in describing how to map between a persistent relational database and an in-memory object representation of business logic. Fowler distills the various approaches to their essence, clearly presents the tradeoffs and defines an intuitive vocabulary to make it easier for development teams to discuss how the patterns apply to their unique application.

Highly recommended.