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J2EE Design Patterns
If you are working on frameworks, integration projects or system components, it is my belief that you'll almost certainly pick up some ideas from this book. J2EE Design Patterns is organized according to the different layers that you might find in a multi-tier architecture: presentation, business, database, messaging, and others. Consequently, if you're a JSP developer on a project team, youll be able to get some ideas for how to organize your work as well as how to interface it with, for example, controllers, if you're following an MVC framework. Or, if you're integrating various distributed non-Java systems, you'll want to read the chapters on Business Tier Interfaces and Enterprise Concurrency.
Judging by my friends' bookshelves, another popular Java patterns book is Core J2EE Patterns. If you already own this book, you will find that this new offering from O'Reilly doesn't contain as many patterns per se, but seems to go into a greater level of detail describing each pattern and supplementing it with more code samples. A nice feature of the O'Reilly book is that each pattern gets ample coverage in enough detail for you to understand the actual problem, the causes and -- equally importantly -- how to put a solution into place. Each pattern is described using some UML notation and code samples (Chapter 2 contains a UML primer).
One of the problems that I've encountered reading books on the subject is that some steer so deeply into abstraction that they become hard to understand. Others are so stylistically repetitive that trying to read them becomes mind numbing. Fortunately, neither problem surfaced during the time that I spent reading this book. The authors avoided the visual repetition of the traditional Problem / UML / Goal / Actors format that other books follow by moving this type of description into an appendix. That lets the body of the book flow more easily and also supplies the reader with a handy quick reference in the back pages.
Do I have any complaints? Well, this book certainly doesn't suffer from any fatal flaws. But it seems that an acknowledgement of the popularity of certain components could have been included. For example, while specific MVC frameworks, like the ubiquitous Struts, were mentioned, Object-Relational mappers were not; I read some of the chapters and winced at the code samples that manipulated SQL strings and felt grateful that I'm using the wonderful Hibernate O/R mapping engine. Of course, for various reasons, some readers won't be able to use tools like these, and a book about patterns has to maintain a certain level of abstraction in order to maintain any lasting credibility. But the section on Object-Relational Mapping doesnt even mention that a class of tools exists without the use of EJB CMP (Container Managed Persistence). Thats a real shame, because manually moving data from the object world to the relational world and vice versa is time-consuming and error-prone (and frequently unnecessary) work.
It's a good book, with 285 pages of text and 53 pages of appendices. I've owned it for four days, and I've already managed to steal some of these ideas for the projects I'm working on.
Philip Jacob works for Eyeglasses.com. You can purchase J2EE Design Patterns from bn.com. Slashdot welcomes readers' book reviews -- to see your own review here, read the book review guidelines, then visit the submission page.
Basically there are common themes in problems, and patterns help with the theme of the problem, not the problem itself. For example, I could want to centralize and pool objects for some reason. The design pattern to solve this kind of problem is basically to make constructors private and use "Factories" (static member functions) that return the objects using static data to keep track of them.
Pattern can be a misleading word because it has too many meanings. You could interpret design pattern as commonalities in design or as a design template (like sewing involves working off of a pattern). It's closer to the first definition than the second.
Just don't follow a pattern that you don't understand exactly how works. You'll end up with more problem than solution. That's why I usually don't like pattern books. Unless you read them like you would a chess book and try to figure out how/why it's a mate-in-2, then you aren't going to get any real benefit from them. Chances are if you can understand how/why, then you didn't need the book to begin with. There's a slim chance that you'll run into a problem and have not used a more optimal solution because you didn't read one of these books, but I don't think it's all that great. Design patterns should be taught in school as exercises for the common problems they'll run into, not really a place to start when trying to solve a problem.
Karma Clown
It's helpful in conversation, in the sense that patterns are tools. For example: it's much easier to say "singleton" than to say "make sure this class has only one instance and make sure there's a way everyone can get to it" -- just as it's easier to say "hammer" than "that thing you bang nails into things with."
evil adrian