This post tells a story about jpa and internal domain specific languages, [...]]]> At the moment I am already home, we had a long drive from 10 hours, a good night sleep, and a day at work. I owe you all the report of the last day at the JAOO and maybe some final thoughts.

This post tells a story about jpa and internal domain specific languages, read on if you want to learn more.

The first presentation I saw this day was by Patrick Linskey. He talked about JPA, a short introduction of jpa 1 and some features of the upcoming jpa 2.

One thing I liked about the overview of jpa 1 is that I actually learned some new tricks. The best trick I missed completely before is the getReference method. When programming a delete method I used to load the object first before deleting it. This is not very optimal. I did not know of the existence of the getReference method.

<T> T getReference(Class<T> entityClass, Object primaryKey)

Using this method you can program your delete method like this:

entityManager.delete(entityManager.getReference(Order.class,17));

What I remembered from the presented new features is the inclusion of features in the specification that all implementations already have. Think about features like: cache handling, logging sql statements, creation of schema. Another new feature is pessimistic locking next to optimistic locking.

The final thing I want to mention is a project that is an abstraction (or dsl like Microsoft Linq) for querying collections or entity managers. This project looks promising. It is still young, I’ll get back to this when I have actually tried it.

http://quaere.codehaus.org/

The last talk I attended was presented by Martin Fowler. Man he was fast, I did grasp the basics of domain specific languages (DSLs). Martin was talking about a book he is writing. The focus was on internal DSLs. I mentioned Linq before, I like the idea. So I will do some more research. I am not going to try to explain what it is about, check the following website of Martin if you want to learn more. Focus on fluent interfaces and builders on top of normal domain type of objects.

http://martinfowler.com/dslwip/

The end of JAOO

So that was the end of JAOO 2008. It was a nice conference. To be honest, not the best content out there. A bit more in depth knowledge, more code, would have been nice. Nevertheless I got some interesting view points. It is clear we have to learn additional languages in the future. I am not sure though which one(s) to chose. Maybe a scripting language? Just more JavaScript, or groovy, we’ll see. For know I’ll focus on things like Flex, GWT and maybe Wicket. On the server side we need to learn more about cloud computing and how to keep your systems in the air. I end with the best thing, especially for some of my colleagues. Everybody must start using timeouts and of course the circuit breaker pattern.

The first [...]]]> From monday to wednesday I am attending JAOO in Denmark with 6 other colleagues. I am not going to give an extensive report, but some notes and remarks might interest you guys. Therefore a brief summary of what I have seen, the presentations I attended and the most interesting things I remember.

The first day in just a few words, not necessarily in order: Linq (why don’t we have this is java?), performance and scalability (still important), programming the cloud (gives new things to think about), google apis (wow there is really a lot you can do), scala (just not my thing), beer (there is enough here)

Read on if you also want to read more details

The first day started of with the key note. It was a talk about microsoft technology. Not interested, well, kinda interesting. It followed the functional programming is the future hype. Talking and showing F#, well oke, not for me. But Anders Hejlsberg also showed Linq. This is more about internal functional programming. A nice abstraction of using sql quesries using fluent interfaces and immutable objects. I reall like the idea and will do some research in the future. Maybe there is a java alternative that I do not know of.

My next session was from Patrick Linskey about designing your aplication for scalability. I liked the talk, good speaker. Some things that I wrote down are

• optimizing IO communication, for instance sing the jdbc prepared statement batching.
• Use synchronization with care when trying to get your multi processor systems to work. The different processes will all have to stop on a synchronization point.
• When needing shared state, we often use a database, it might be much better to separate your tiers. You could create a service tier with ejb’s for instance.
• Other languages like Scala or Erlang support concurrency out of the box. Not that they are perfect by the way, see my later comment on scala.

Gregor Hohpe talked about programming the cloud. This was a very good presentation and an interesting as well. Using a cloud for doing processes or store data is different than our every day database app. Think about big websites like flickr, google search, facebook. They do not use two phase commit. They use other ways called compensation. W as users learn how to compensate for things that go wrong. Our programs should act in a similar way. A nice comparison is two phase commit and starbucks, just google for the article. Another comparison I liked was ACID in the traditional transaction way and his ACID. In traditional way it is about Predictive and Accurate, in the new way more about Flexible and redundant. As a side step, Gregor talked about the google api’s. I was surprised about what you can do with the apis of for instance google calendar. I had to try out the google platform using python. It was very easy to do, my first tutorial is published within half an hour. You can look at it here. http://jettrofirst.appspot.com/. If you want to learn more about google apis go here : http://code.google.com/apis

After Gregor I went to Jonas Jacobi, a guy I knew from the past days when doing Oracle UIX. He know is working for a small company called Kaazing. He demonstrated avery interesting project called the Kaazing Gateway. It is an open source implementation of the upcoming HTML 5 WebSocket. Not that it is supported by any browser, but they have found a way to use the flash plugin to overcome this problem for now. What it is about? Real push technology. Opening a tcp/ip connection with a neat trick of downgrading the HTTP connection. That way you do have the full duplex connection an push technology becomes reality. It is a very interesting technology that I will try out in the near future.

The last presentation of day 1 I attended was not the best one. I wanted to hear something about the big buzz scala. I am going to be short. There are two possibilities: the first is that Bill cannot realy explain what it all is about, the second is that scala is just not my thing. To much of a coupling between the normal implementation and the functional programming way. Hard to read, not to maintain.

That is it for now, we ended the day with a good meal and enough to drink.