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Hibernate in Action
Well, I am glad to tell you that this is not just a dump of the on-line docs. The book not only gets you up to speed with Hibernate and its features (which the documentation does quite well). It also introduces you to the right way of developing and tuning an industrial-quality Hibernate application. I consider myself a pretty seasoned Hibernate developer, being familiar with the API since its 1.2 version in Q1-2002 (if I remember well the first app when we used Hibernate). However, I was proved wrong by Hibernate in Action, which describes best practices and even API features that were unknown or vaguely known to me. That is, until now.
The first chapter, in the good tradition of all first chapters in the world, is an introduction. It's a very well written introduction about why do we need ORM solutions in OO applications. The chapter explains the O/R impedance mismatch, while declaring quickly that OODB sucks (immature and not widely adopted). Wel'll also find out that EJB also sucks from a persistence point of view (for various reasons). Which can be quite a surprise knowing that Gavin is one of the authors of EJB3.0 specs. Or, on the contrary, this will explain a lot of things in the new EJB specs.
Now that we have cleared the "why Hibernate" issue, let's continue to the second chapter. Which - tradition obliged - is a "Hello, world" and a "Let's get started" chapter. Here you go: almost 50 pages later you should be able to write simple Hibernate-based persistence layers and integrate within an application server, like for instance ... Jboss ! Humm, well, why not ? They are sponsors of the Hibernate project, after all.
In the 3rd chapter, our fresh knowledge will be put to good use by starting the development of an online auction application called CaveatEmptor. This app will follow our reading progression and will grow bigger and smarter chapter by chapter. But for the moment, we are at the inception phase. What gives: a little bit of analysis, a stylish class diagram of the domain model and the resulting mapping file. And if you thought (based on 2nd chapter) that the mapping file is very intuitive and simple, you're in for a big surprise -- it is, indeed, intuitive and simple! Quite bizarre for an open-source project. As a matter of fact, the mapping file is one of the pivotal elements of Hibernate, since it addresses directly the O/R impedance mismatch, a recipe for transparent linking your POJOs and the constrained relational model. No wonder that a big part of this chapter is aimed at explaining why and how the mapping works in Hibernate. You'll see how class associations and inheritance translate at the metadata and mapping level. You'll start to understand the things that you took for granted in the previous chapter and you'll have that pleasant "uuh, I see" chain reaction. Hold on, it's just the beginning.
Because chapter 4 is going to explain once and for all the lifecycle of persistent object in Hibernate, their behavior from a persistence point of view as well as the available fetching strategies. And if you thought you already knew everything by heart from the documentation ... well, maybe you do know everything by heart. Nevertheless, it's very well synthesized in chapter 4 and I'll recommend it anytime to a coworker eager for Hibernate knowledge.
In the next chapter (the 5th) the rollercoaster slows down a bit. That is, if you already know the behavior associated with the four possible isolation modes in transactions, what are the different types of locking, what (the hell) MVCC means and the importance of transaction scopes. Chances are you already know some of this stuff quite well, but everybody needs a refresher from time to time, especially when it's well explained and when it comes with versioning and caching (1st and 2nd level) in Hibernate as a desert. By the way, I thought that OSCache supports clustering, not only SwarmCache and JbossCache, as stated in the book. There's even a thoroughly explained example of using JbossCache as a level 2 clustered cache for Hibernate, but it shouldn't be too hard to convert to other types of caching systems.
Now, if I were the author of the book, I would have placed chapter 6 before chapter 5. But I am not the author, which is quite fortunate for you dear readers since Christian and Gavin are much more competent than me at writing books about Hibernate (and probably at some other unrelated domains). They have decided to go back to mapping in chapter 6, after the short transaction/caching intermezzo. Well, they should know better... it's time for a serious dose of advanced mapping. This chapter is attacking interesting subjects such as custom mapping types (simple or composite) and (finally) the mapping of collections. Special guests stars: the whole gang of "sets, bags, lists and maps", together with explanations about their relational equivalent (associations, associations and associations !). Oh and yes "polymorphic association" (section 6.4.3) - I wasn't even aware that Hibernate is able to do that... guess I'm not that 'seasoned' (as a Hibernate developer) after all.
The 7th chapter is about "Retrieving objects efficiently" : about 45 pages for the 'retrieving' part and 6 pages for the 'efficiently' part. Fair enough ! You'll learn how to master basic HQL queries (parameters, pagination ...). You'll get a grip on the query by criteria API, as well as on advanced stuff such as dynamic queries, filters, subqueries and native SQL (very powerful). At the end of the chapter there's the Hibernate-specific solution for the n+1 selects problem, query caching and result iterators.
Following this wealth of useful knowledge, the 8th chapter starts a bit dry. Nevertheless, after a short introduction about Hibernate in managed environments, you'll find yourself again in the land of advanced programming techniques : application-level transaction implementation ! This is mostly new stuff (at least for me) - a great collection of best practices for transactional behavior management in industrial-quality apps. Somewhat unrelated but still interesting, the chapter ends with legacy schemas integration and a smart implementation example for audit logging.
The 9th (and last) chapter is about the round-trip development in Hibernate using the classical toolset : Middlegen and/or hbm2java and/or XDoclet. All the available techniques are presented in a very detailed, step-by-step manner.
Wait : don't close the book, there's more ! Ignore Appendix A (a short and rather uninteresting document about SQL fundamentals - that is, if you know SQL). Appendix B contains mildly un-fascinating ORM implementation strategies pour les connoisseurs (come on guys, I'm just a dumb user). But - Appendix C is a great collection of real-world stories and by all means read them all ! Especially the last one, a treasure of hard to find knowledge (no spoilers, please...).
In the end, I have to confess that there is something truly interesting about Hibernate In Action : albeit very technical, it reads astonishingly easy - and this kind of books is unfortunately very rare nowadays. My congratulations to the authors for this excellent piece of work - it was worth the wait.
As for you dear potential reader, if you already know all the information detailed in the book, I bow before you, great Hibernate wizard.
You can purchase Hibernate in Action from bn.com. Slashdot welcomes readers' book reviews -- to see your own review here, read the book review guidelines, then visit the submission page.
well, I overslept Sunday morning, does that count?
CBV*()$#
free ipod and free gmail!
What is Hibernate and what does it do ? I think the article failed to mention that can anyone please tell me what it means.
Johnny English
Jeez, with a manual that big it should be named coma.
Weaselmancer
rediculous.
However, for my Java consulting business, Prevalyer is definitely my new "secret weapon". With a little care, it is easy to set up your POJO classes so that you can add class attributes without breaking your persistent Prevayler object store. Using Prevayler reduces development time. Good stuff.
It always drives me nuts when I see a story about a given software package that talks about it's greatness... but that does not simply say what it is. This is made worse when the it's homepage which I'm sure describes the given package is /.ed.
Help Brendan pay off his student loans
I really wish the story submitter would have taken a moment and put a one or two sentence explanation of what Hibernate is. It's not exactly a descriptive name, which I'll concede is common in our industry.
Hibernate is an API for Java that uses Java Beans (get() and set() methods for all properties) to create, read, update and delete rows from a database. It's really cool. It's sometimes called JDO (Java Data Objects) but it's a dangerous association because of the Sun Reference Implementation of JDO, which is its own specification. Hibernate is different.
Attention deficit disorder is a complicated issue, spanning several major... HEY LET'S GO RIDE BIKES!
I hope that the book is better than the review. The reviewer starts off with the most basic assumption that ANYBODY with a CLUE knows EXACTLY what Hibernate is. Perhaps that's why hibernate.org isn't responding right now, because everybody read the top story, found no description of Hibernate, and clicked on the hibernate.org URL as the most likely place to find a description of Hibernate.
-russ
Don't piss off The Angry Economist
This article just seems like a bunch of open source NewSpeak, I swear to god every time I try to read and understand what this is about my brain shuts down... quack quack RTFM quack quack OODB quack LGPL...
It's a very well written introduction about why do we need ORM solutions in OO applications. The chapter explains the O/R impedance mismatch, while declaring quickly that OODB suck (immature and not widely adopted). Wel'll also find out that EJB also suck from a persistence point of view (for various reasons). Which can be quite a surprise knowing that Gavin is one of the authors of EJB3.0 specs. Or, on the contrary, this will explain a lot of things in the new EJB specs.
Now that we have cleared the "why Hibernate" issue,
Yeah... Cleared that right up. ORM? O/R Impedence? OODB? EJB? Little help here?
Give me Classic Slashdot or give me death!
Rather than sharing my theories about a top-secret-yet-LGPLd government project to develop object-oriented Java-based SQL/graphics library that will allow us to train secret UFO pilots to defeat an invasion of alien accountants, would someone care to fill me in? I would be forever in your debt.
Carousel is a lie!
I think it's interesting there's not more really exceptional documentation for F/OSS projects.
OSS Coders tend to have the fantastic attitude of always improving whats been written before, of making it better & better, revising, patching, rewriting, until an application becomes so damned useful there doesn't seem to be any other realistic choice.
All well and good when it comes to coding - but where are all the documentation geeks to do likewise?
doesn't explain what hibernate is, and the server's already /.ed. Damn. I guess I'll have to die without ever knowing.
Maybe if you take a long nap the site will be back.
I still prefer directly writing the SQL code myself. It doesn't take that long, and for many things it seems to be more efficient. I only pull the fields that I need.
I have seen many applications where a developer will pull a list of objects out of a database and only use a small percentage of what was pulled. This was caused by a heavy persistence layer abstracting what was happening, and a developer that didn't care to find out.
I seem to be in the minority with this view though. Automated persistence is quite trendy.
Usually I am able to BS my way through an article by making a guess based on the title. This article. however, posed a problem to me... I couldn't figure it out, or rather the decision I made wasn't that logical.
Based on the info in the title, I concluded that the project did nothing (after all, a successul implementation of hibernation just sits there.) This caused me much confusion, resulting in me mistaking salt for sugar, and baking soda for non-dairy creamer....
...Remember kids, think before you post...
The real litigious bastards...
"The R Project for Statistical Computing"
http://www.r-project.org/
This is an amazing stat program that is open source with a lot of documentation backing it up.
Some of the documentation you can download:
An Introduction to R (approx. 100 pages, 650kB)
The R Reference Index (approx. 2300 pages, 12MB)
Also, under their contributed documentation section, they have the documents sepearted by "Documents with more than 100 pages" and "Documents with less than 100 pages".
Its not what it is, its something else.
It's a object relational persistence Manager for Java, kinda like JDO. Nifty little tool so you don't have to make your own persistence calls with JDBC, saves a lot of keystrokes. I bought the book and it shows a lot of different tricks, and with Hibernate's QBE (Query By Example), saves a ton of time debugging dynamic SQL Calls.
I've been using this for quite a while, coupled with Spring you can write a lot of robust reusuable objects, if you utilize java's OO design methods.
"It takes many nails to build a crib, but one screw to fill it."
When people release source under L/GPL, you'd think they'd want people to use it, and contribute back. It's really hard to do that when the code is inaccessible for lack of documentation. Even reading code that is commented (a rarity) is no substitute for an overview - relying on "grep" is no way to trace codepaths or marshal APIs. At least CVS requires a note on checkin, even if it's usually a vague "fixed bugs". If you're not going to write your code starting with a first pass of all comments, with clear, consistent variable names, at least include a description of each code file's function in the grand scheme in its header, and usable README and INSTALL files for the whole project. Most important, have someone not on the design/code team read the docs for usability by a stranger. Beta testing the docs isn't hard, and you get to gloat about your brilliant achievements in words that don't have to compile.
--
make install -not war
So many initial posts asking what Hibernate is when it is probably the poster child of Java Open Source (OK JBoss might be better known but unlike JBoss Hibernate is universally well regarded). Disappointing really.
Do not try to read the dupe, thats impossible. Instead, only try to realize the truth
What truth?
There is no dupe
However, for my Java consulting business, Prevalyer is definitely my new "secret weapon". With a little care, it is easy to set up your POJO classes so that you can add class attributes without breaking your persistent Prevayler object store. Using Prevayler reduces development time. Good stuff.
Good Lord.
This post, while informative, just makes me want to go to sleep. Or quit my job. Or both.
Maybe I chose the wrong career.
Are Java class mappings to databases really all that exciting?
In the course of every project, it will become necessary to shoot the scientists and begin production.
nonsense, no human mind is capable of dealing with the immense complexity of SQL. Why, databases were just huge excel spreadsheets until smart OO developers figured out how to store... i'm sorry, of course i meant "Persist" objects in them. And don't forget the rallying cry of the modern developer: "the database is the bottleneck".
/twisted & bitter
#!/usr/bin/english
I sometimes do the same thing myself (i.e., just write a little code using the JDBC APIs to grab what I need).
Also: with Hibernate, you do have control over how much of a row of data you actually retrieve since you specify the mapping that you want in an XML configuration file.
Do try Prevayler however: for some applications it really is a great tool. I especially like it for web applications where most data access is read only: caching objects in memory really speeds things up.
I have used Hibernate on the last two J2EE projects I've worked on and can attest to its simplicity and power. Although it'll take you a few weeks to really get the hang of how things work under the hood, it's well worth the learning curve. And it's ridiculously simple compared with EJB - that's for sure. My latest project even involved storing CLOBs to an Oracle Rack cluser - it took a bit of tweaking and research, but we saved ourselves hundreds of lines of codes and it performs without a glitch. ;-) :-)
Okay, I haven't RTFA, but the poster should also have made mention of Spring, which works hand in hand with Hibernate. Spring basically is an Inversion Of Control (IOC) framework, that allows you to define Hibernate transaction and session contexts. Spring also offers a great MVC layer, but one does not have to use that. If one chooses to just use Spring as an addition to Hibernate, one can look at Spring's additional functionalities as needed. Spring also offers Oracle BLOB/CLOB support by offering a customized OracleClobHandler - Oracle ONLY supports its propietary CLOB objects and won't accept java.sql.Clob objects via Hibernate.
Generally, Hibernate is very non-intrusive and gives you the opportunity to write JDBC code alongside with your Hibernate code (which is super-elegant and abstracted the way it should have been done a long time ago). So, it can be slowly folced into an existing project without having to refactor any legacy code.
The Hibernate user group is a bit rude to be quite frank - I've tried to post some questions in the dev group and got pretty angry replies. The 'beginner' group was not very helpful, so I had to google for answers. Of course there's the book, and I would strongly recommend to get it, since it is one of the major revenue sources for those Hibernate contributors. We want open source, but we can't expect to get everything for free, right?
My first exposure to Hibernate was through the Appfuse framework, which is an excellent J2EE kickstart project, complete with ant built, Xdoclet, Hibernate, Spring, the works. I was even able to use XDoclet tags inside my Java beans, relieving me of having to write my Hibernate definition files by hand! It really doesn't get much easier than that. For anyone wanting to give Hibernate/Spring a try, I recommend to download the latest version of appfuse and give it a try - it's a liberating experience. The biggest kick I got was being able to seamlessly switch my project from Oracle over to MySQL by simply changing a few environment variables - I mean, how cooler can it get?
Hmmm, *looks on hard drive*...
... the list goes on, of course ...
a 7000-word document on configuring ALSA drivers
a 400,000-word document on using MySQL
a 700,000-word documentation set for Perl (just the core, not counting add-on modules)
6.5MB of Kernel docs
27MB of Gnome help
Nope, that's not a particularly outstanding trait. If he had talked about this documentation being well integrated with other, related documentation-sets, then I'd find that interesting (rarely is this the case in open source software), but it doesn't sound like it is.
Hibernate is what their server is doing right now after the vicious slashdotting that it just received.
Another lame /. article; what supposedly is an "overview" tells us nothing and is so full of TLA and such that you have to know what they are talking about to even make any sense of it. Clue for timothy: If you're introducing something new in a lead page /. article, it would be nice to actually tell people what it is, cutting through three letter acronyms and other buzzwords that can only be understood in context , which is missing when the reader has no reasonable expecation of knowing what the hell you are talking about!!!
I'm an American. I love this country and the freedoms that we used to have.
Summary: zzzzzzzz
It's 10 PM. Do you know if you're un-American?
Actually, this entire article is proof of how...
- ...program names are getting more pointless by the day (Hibernate?), and...
- ...how most programs are mostly hype (more buzzwords than a Dilbert book).
I'm sorry, but there's no excuse for the utter disregard to using common sense that was exhibited in the "hibernate" developers' group. People wonder why Microsoft can sell shoddy products. Well, I'll tell you why: they give them meaningful names (Word processing: WORD, Development studio: STUDIO).To the people at hibernate.org: you should be ashamed.
Notice this quote by one of the Hibernate developers in an interview earlier this year:
"I went into this knowing very little about ORM, and even very little about databases. One of my first tasks was to go out and buy a book to learn SQL properly. All my understanding of the problem comes from what our users have taught us over the last two years."
Sigh... basing a product on secondhand experience from users who probably have never even learned what the relational model is really about.
If Hibernate is your poster child, you need a new child. Or poster. Or analogy. OR maybe its like a child poster on a milk carton. Have you seen this technology? It was last sighted in 2001 shortly after its birth.
Well.. maybe. Or Maybe not. But Definitely not sort of.
Anyway, the point is the site doesn't do anything to elucidate the limitations on ACID compliance, querying capabilities, etc. that you would expect from an object database system. Hell, they don't even seem to recognize that Prevayler is just a limited subset of an object database system (i.e. a memory-resident one). I'm glad somebody has written a reusable chunk of code to do this and all, but I wish the people doing it were more aware of the theory behind databases, and what trade-off decisions they were actually making so they could better document and explain them to their users.
Anyway, if you are just comparing it to MySQL (hehe) I'm sure there are lots of great use cases for Prevayler, but when you compare it to a real RDBMS and look at real enterprise application usage scenarios, it's a bit of a different situation.
Hahahaha. Good one ;)
Don't forget, many modern developers haven't yet figured out that abstraction and performance are in an inverse relationship.
But with all this new hardware and great software running on it, we don't have to worry about silly things like memory usage and performance tuning anymore! The magic box does it for us!
:(
I just made me sick
Slashdot is proof that Sturgeon's Law applies to mankind.
You're right, there is no information in the article. It doesn't even tell us what Hibernate is. The blather is also peppered with undefined acronyms - ORM, POJO, HQL.
And some idiot moderator modded parent down as a troll. Sigh. It's not a troll, it's a valid and accurate criticism of a really crap article. Crap is, unfortunately, becoming the Slashdot-article standard.
I hope that helped.
Not true. It took me a LOT more time learnng how to write good JDBC code, that didn't break in an enterprise enviornment. Had I had access to Hibernate back then, my life would have been infinitely easier. Finally, Gavin actually offered a cash price for anyone writing manual JDBC code which would be faster than Hibernate - so far nobody has come to collect it.