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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.
Conincidently a co-worker/cow-irker of mine just borrowed my copy. The nice thing about it is it gives some names to ideas a lot of us already use, making it easier to talk about them.
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I am a fan of design patterns but many of the patterns I see described in these books are workarounds for weaknesses or performance issues in the J2EE specs. In many cases a "best practice " tag is more appropriate than a design pattern.
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I remember commenting on some other topic regarding J2EE design patterns recently.
....
Like I sort of said that time, the design patterns are mostly just workarounds for a bad system. My advice is 'use JDO' and avoid all these problems (this is coming from someone working on both a JDO and a J2EE system right now).
I do in fact have one such EJB design patterns book, and its crazy the lengths they go to to make a broken system work
- Its too costly to make calls to an EJB's individual get methods - make a value object for each EJB!
- Don't like making all these extra objects, and coping with the extra maintenance required, and writing all the methods to transfer values between the EJBs and these objects? Transfer the information using a hashmap!
- Don't like the loss of all the advantages of using OO programming languages and entity beans instead of SQL which comes from passing everything with hashmaps? etc etc
Enough to make any experienced _object oriented_ programmer pull their hair out. Of course, if you prefer using the buzzwords of 'EJB design patterns' to the practicality of JDO then go ahead, code an EJB application - enjoy developing in an environment where the deployment required to test any changes is 5 minutes plus for any decent sized EJB project, where your $10,000s EJB server can't work out how to handle basic relations in the right order, and where you have to code half of your queries in SQL anyway (i.e. see the 'Data Access Command beans' pattern which the book no doubt has) as the system is so slow and not powerful enough.
It's pretty interesting to see where some of these modern day architects got their ideas and that patterns occur in things all around us in our everyday lives.
It's also required reading for anyone REALLY serious about playing Sim City.
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