Bitter EJB

Michael Yuan writes "Enterprise JavaBean (EJB) is one of the most widely used technologies in enterprise Java. It is designed to be a scalable and flexible distributed framework. In EJB, almost everything can be done in several different ways and it offers the developer the maximum flexibility to choose the right approach for the project in hand." Yuan provides a review, below, of Bitter EJB, to guide programmers interested in large-scale Java development. Update: 10/27 18:27 GMT by T : Peter Wayner provides a somewhat deeper look at the book as well, also below. Bitter EJB author Bruce Tate, Mike Clark, Bob Lee, Patrick Linskey pages 412 publisher Manning rating 9 reviewer Michael Yuan, Peter Wayner ISBN 1930110952 summary Anti-patterns in Enterprise JavaBean development

However, every coin has two sides: the other side of "freedom of choice" is "complexity". Although EJB is an incredibly powerful tool in the hands of experience architects, it is subject to a lot of misuse by novice developers who do not make sound choices. For example, some developers might use a BMP entity bean to map each database table in the system; or access entity beans directly from a distributed layer; or store large amount of data in session objects ... The list goes on. Although those approaches are technically possible, they are hardly the most efficient ways in most cases. Such problems have not only caused many projects to fail but also tarnished EJB's reputation. In fact, the complexity of EJB is often quoted as an argument for other enterprise platforms.

For EJB developers, it is crucial to learn from other people's experiences and follow proven best practices. That helps to reduce the complexity of the platform. Manning's "Bitter EJB" is a very timely book written by well-known experts in the EJB field: Bruce Tate, Mike Clark, Bob Lee and Patrick Linskey. Unlike other "architectural" books, Bitter EJB teaches best practices through common mistakes (anti-patterns). It focuses on "what not to do" but still encourages developers to come up with liberal (everything not forbidden is OK) and innovative solutions. After all, EJB is about flexibility and freedom of choices.

Part I of the book is an overview of anti-patterns in the EJB specification. The EJB specification itself has several major design problems when it first came out in March 1998. EJB v1.1 and v2.0 have gone great length to fix the anti-patterns in the specification. But early adopters may have already developed some anti-patterns in their applications. For new developers, the history also serves as a valuable lesson on what EJB is really for and how different components in the specification fall into their current places. In this part, the authors also provide an excellent recount on what went wrong in the high profile TSS Java PetStore benchmark.

Part II is about session and message-driven beans. Those beans are mainly used in the integration layers. Topics covered in this part include how to deal with large database results, whether to maintain session states, the limitations of XML and much more.

Part III covers EJB persistence. Entity EJBs are probably the most confusing types of components. Many experts have advocated to abolish entity EJBs altogether in favor of other simpler persistence frameworks such as the JDO or even simple JDBC facades. The authors discuss the pros and cons of entity EJBs and covers most leading alternatives. For those who must use entity EJBs, this book also offers useful advices on a range of topics including how to reduce round trips, shorten primary keys and handle expensive database joins etc.

Part IV covers broader topics including performance tuning, testing, building and packaging. One big problem that even EJB developer can recognize the complex deployment descriptors. One chapter of the book is dedicated to reduce code duplication, automate the deployment process and avoid the "integration hell". The last chapter of the book provides an overview of "what's next" in the EJB space.

Overall, it is an excellent book for all EJB developers and other enterprise developers who want to learn from the successes and failures of EJBs."

Peter Wayner's review:

Although there may be as many 36 plots in all of literature, the compartively new world of computer books has really had only one: this new technology is simple, very simple, and it will make your life better and your teeth whiter. Bruce Tate opened up a second plot in his book Bitter Java by exploring just how even the best programming ideas have dark sides. Now he's back with three other authors exploring the world of Bitter EJB.

This book is more fruit from the same tree. Or, to hack the Java MemeStream even more, more beans for the same mill. If you use Enterprise Java Beans (EJB), or think about using them, you should read this book to see what can go wrong. The title shows how naming schemes can be misleading because either the authors aren't really that bitter, or because they're focused entirely on EJBs. This book does not belong in the same camp with the Java==SUV crowd. These authors are really admirers who just want to warn people how to avoid problems with Java and EJB.

Tate and his new co-authors, Mike Clark, Bob Lee, and Patrick Linskey are all consultants who seem to use Java a lot, at least when they're not cheating death. One of the cuter grace notes in the book is a collection of war stories from extreme sports that are mixed in as an allegorical taste of what's to come. Before exploring the problems with a Java concept known as enterprise beans, they tell a kayaking story that ends with the sentence, "Then we hear a loud crunch and look up to see Eric's stern stationary at the top of the drop, revealing the sitaution that every kayaker dreads the most -- the vertical pin."

After stories like this, the book goes on to explore just how the very fancy enterprise beans toolkit can produce an application that moves slower than a stream filled with honey. Each chapter is filled with antipatterns, or lessons about the software learned the hard way. They're sort of like points on the map that say, "There be dragons here."

The book is divided into four parts. The first section, termed "The Basics," explores the simple ways that EJB technology goes bad. The toolkit was heavily hyped as the perfect solution for building business websites that interface seamlessly with large databases. As the business grew, new servers could be added without grief. Alas, as this section points out, there are many reasons why an elephant gun can be the wrong weapon for getting rid of mice in your house.

The next section on "Networks and Messages" describes how good ideas can turn into slow code when people misuse the fancy tools for scaling EJBs. In theory, the EJB toolkit will split up processes simply across multiple machines to handle more customers, but in practice all of the communication can slow things down considerably.
The section on "EJB Persistence" describes how the much-hyped system for seamlessly storing away enterprise beans in databases can weigh down a system. My only beef is that they left out much information on Prevayler, a much-maligned and misunderstood ultra-light toolkit that is like an anti-EJB persistence layer in every possible way. I'm enamored with it, if only because it's such a radical move away from the monolithic APIs like EJBs. While they liken using EJBs to snowboarding in fresh powder with a 100lb pack on your back, Prevayler is sort of like boots-only hiking.


The last section isn't about EJBs per se, but similar toolkits and projects that often get used with EJB. There are antipatterns to avoid with JUnitPref and Ant, too. Some of these suggestions, like some in the rest of the book, aren't terribly new or brillant, but it can't hurt to get another lecture on the importance of testing your code.

The book shines when it's exploring what goes on behind the slick facade of the API. Sure, the EJB toolkit will dutifully load up data from any object on any server in your farm, but you better be careful invoking some of these these methods because the network is slow. The book often points out how invoking that one simple method from the sales literature can start up dozens of sluggish threads. Peeling away the layers helps understand and explain why the system fails.

Many of these lessons aren't limited to Java or EJB. I wouldn't be surprised if the group of authors was busy rewriting the book with examples from .NET. Unfortunately, some programming problems are very hard, and building a toolkit with a simple API won't make them go away. In fact, the simple appearance can cause more trouble when the programmer can't understand what the secret mechanism inside is doing. Almost all of the problems in this book arise from programmers who believe the sales literature when it tells them not to pay attention to what that little bot behind the curtain is doing. If you're working in the world of EJB consulting on big iron, then you've got no choice but to start thinking about what's behind that curtain.

You can purchase the Bitter EJB from bn.com. Slashdot welcomes readers' book reviews -- to see your own review here, read the book review guidelines, then visit the submission page. Peter Wayner is the author of 13 books including Java RAMBO Manifesto and Translucent Databases.

Comments

Languages need novices, novices need good books.

[Squeebee]

"Although EJB is an incredibly powerful tool in the hands of experience architects, it is subject to a lot of misuse by novice developers who do not make sound choices."

At least the novice developers can use it. Look at Visual Basic: VB is the most popular language with over 3 million developers simple because anyon can pick it up and get started, this leads to more developers, which leads to more apps, which helps Windows dominate the desktop.

Now a large number of those first projects are garbage apps, but at least they give a starting point. We need languages that novices can jump into, then good books that can help steer them as they continue learning the language.

Worth Learning?

[humandoing]

How many people have had really good experiences with EJB's? In over 3 years of doing Java development I have yet to hear anyone say anything good about developing with them.

The vast majority of people who I have talked to seem to indicate that they have never come across any project under development where using EJB wouldn't be complete overkill, and that much simpler, easier to maintain, and cheaper solutions seem to be the path chosen.

These aren't all small projects either, I would venture to say all of the people I have spoken with (or projects I have been working on) have been in the $50,000 - $2,000,000 range, and none of the senior developers or architects on these projects have ever dreamed of going anywhere near EJB.

Thoughts?

Re:Worth Learning?

[_xeno_]

I was going to post something like this too, but I think I'll chime in with some other questions too.

Namely, whenever people on Slashdot complain about how EJBs are insanely slow and seem to cause more problems than they solve, someone always posts something along the lines of "they weren't used properly." Which is nice and all, but I have yet to figure out what is a proper use of EJBs. So, that's my main question - what should EJBs be used for? When are they the right tool for the job?

I wasn't able to figure this out the last time I worked with a J2EE environment. All in all, it seemed that they were too complicated for what we were doing. And I wasn't able to see a problem where they would have been a good solution.

Of course, I've been soured to them (or bittered, maybe?) based on the project which was basically people questioning the contractors' choice of CORBA on their Java-based system. Someone suggested to management that the contractors should have used EJBs and that this would have made the finished project "Better." So I got stuck with the task of trying to demo a system with CORBA replaced with EJBs instead - never mind the fact that most J2EE environments use CORBA as the RMI layer between beans...

So to sum up: What is the "right way" to use EJBs? And what types of problems are they best at solving?

Re:Worth Learning?

[icebattle]

I'm an architect working on a multi-million dollar enterprise app, and our experience with ejb thus far has been extremely positive. We steered away from entity beans, opting instead for a jdo layer. Much of the integration layer utilizes mdb's for bridging between an oracle backend and a db2 subsystem.

With modest hardware we're competing quite effectively with the mainframe app we're replacing.

Our worst choice was to use a Swing front-end instead of Struts.

My advice for anyone getting into ejb development is DESIGN. DESIGN. DESIGN. Know exactly what you're trying to do. Prototype a lot. Test all the time. And get a quality dba, because the effect of solid db tuning will usually beat anything you can do at the app server level.

The main mistake of EJB.

[Krapangor]

They confused complexity with usefulness.
A system with complex rules isn't necessarily more powerful, but it's usually more difficult and error prone.
Unfortunately this misconception is very common in computer science. People tend always to create complex APIs/infaces and protocols just to get a "powerful tools". The result is the security and error ridden state of the internet and computers we see these days.

Strangely other hard sciences have seen these problems decades ago (sometimes even centuries ago) and changed their terminology and fundations accordingly. Take e.g. Mathematics with is based on 2nd order logic and set theory. And this started with Godel, Riemann, Abel and Gauss about 120 years ago. We have the same drive now in Physics with Wolfram and co. propagating simple cellular automata. Some people in string theory move in this direction, too.

Unfortunately computer scientists seem to be immune to this amount of common sense right now. Perhaps they need some centuries of fumbling aroung with overly complex model, too, until they get back to earth.

Incidental success...

[Fnkmaster]

If EJB can be used to put together a scalable, efficient, powerful system, it's surely only incidental. My problem with the EJB model in general is that there seem to be far, far more ways to build systems that don't scale, make inefficient use of resources, and generally suck than there are ways to make a system that scales, works and doesn't suck. Sure, you can say that of any programming language, I know that. But I'm looking at other "whole system" APIs that I can think of.

For example, most GUI toolkits. Usually, you follow the examples and tutorials as a model, you read through the API docs, and you can build a system that works pretty well. Even many other kinds of enterprise software infrastructure - take TIB Rendezvous, or similar messaging systems - I've written apps with many of them that scale, are efficient and work well on the first try.

I've seen several EJB apps written, and worked on a few myself, and you can read all the damned API docs, follow Sun's examples, read your app server documentation, and so on, and still, you just shoot yourself in the foot. This isn't the first book on patterns and anti-patterns of EJB usage, it's the umpteenth. Why? Because the EJB model was so poorly thought out prior to its implementation that if you follow the specs and build the kind of system they _seem_ to want you to build, it just doesn't work.

Instead you need to have built 10 systems that don't work before you have a clue how to make one that doesn't. Frankly, it seems to me like more trouble than it's worth for what you get (which is basically transaction-aware objects, at least based on my knowledge from the EJB 1.1 era). If you just use session beans, if you don't use entity beans, if you don't do distributed transactions, if you don't use stateful session beans... then you can build an app that works.

Great. I think the J2EE APIs have a lot of great, great stuff in them, but EJB just tweaks me out. Why the hell didn't somebody try using this hunk-a-junk before they released their 1.0 spec, or maybe their 1.1 spec, or howzabout the 2.0 spec? Maybe things are better these days, but if your API looks like it's supposed to provide a pattern for enterprise database applications, shouldn't it actually do that, or somehow redefine what the hell it's really supposed to be for?

Is EJB dying?

[MSBob]

You don't have to be a Kreskin... blah, blah.

That's how every good slashdot troll should begin. But if there is one technology that is currently at real risk of extinction in the Java world it is EJB. Almost every new J2EE project that I hear about steers clear from EJB towards simpler solutions such as plain servlet/jsp with JDO for persistence. Then you scale it horizontally through mod_jk or a hardware load balancer. No need for confusing (and restrictive) enterprise beans.

Entity EJBs have been critisized many times and rigtfully so. Session beans I find are OK but for me (and my company) it's a case of "I really don't need them given the baggage of complexity and the restrictive nature of their API.

Message driven beans are probably worthy of consideration but there isn't that much to them really. Certainly not something you couldn't implement on your own with plain JMS. I've done it, didn't take much time and it worked just as well as the specc'ed MDBs. And I don't have to run within an EJB container. I can deploy to Tomcat and have SonicMQ running remotely.

Is EJB going to really take off? Seems that the spec was vastly improved but not all problems with the technology have been addressed and then there is the phsycological issue for many developers who had nasty experiences with EJB 1.1 development.

I won't trash EJB they are a certain way to develop enterprise applications. I just find that I end up with much simpler design if I avoid them in lieu of something simpler. My preferred stack at the moment (assuming no legacy systems to integrate with) is as follows:

• Struts
• Hibernate
• GLUE
• Tomcat
• JDOM
• SonicMQ if I need messaging
• Good DBMS

And I'm good to go. Look Ma, no EJB!