Technological Thoughts by Jerome Kehrli

CommunityBoard : a sample multi-module maven / glassfish / eclipse Java EE project.

by Jerome Kehrli

Posted on Sunday Oct 24, 2010 at 10:29PM in Java

CommunityBoard is a sample multi-module maven / glassfish / eclipse Java EE project.

It realizes is a little Forum / Note publishing application. Its main purpose it to act as an introducing laboratory to Java EE programming. As such the functionalities are rather limited. Yet it covers the most fundamental aspects or issues with Java EE programing in the way it show hows to :

  • write entity beans with bi-directional relationship;
  • use these Entity beans in EJBs (Stateless session beans);
  • use other EJBs in EJBs;
  • use EJBs in a servlet or a JSP located in a WAR (i.e. no processing of the @EJB annotation);
  • build a multi-module Java EE maven project with jars, wars, ears;
  • how to write JSPs with the JSTL (Ok I am not very proud of these JSPs yet they do the job) and
  • deploy a multi-module ear within Glassfish and use a container defined datasource

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Funny developer tale

by Jerome Kehrli

Posted on Thursday May 06, 2010 at 11:03PM in Computer Science

I've been working a few years ago on an architectural concept for some very specific piece of software my former company had to develop. The technical challenges were huge and the field was pretty complex. In addition, the timeframe was very little and we have had to rush a lot to get it ready and prototyped in time.

In the end we screwed up ... totally. The concept was miles away from what was required and we pretty much had to start it all over. Months of work were just good enough to be thrown away with the trash.

Not used at all to such failures, I decided to take some time to understand what happened, what went wrong.

My investigations led to the following story, a pretty funny though quite common developer tale.

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DWR : A paradigm shift in web development

by Jerome Kehrli

Posted on Thursday Apr 29, 2010 at 04:57PM in Java

I discovered DWR recently and I believe it to be an amazing breakthrough in the world of HTTP client-server comunications.

First what is DWR ?

DWR stands for Direct Web Remoting - Easy Ajax for Java.

DWR is a Java library that enables Java on the server and JavaScript in a browser to interact and call each other as simply as possible.

Quoting the official website :

"DWR is a RPC library which makes it easy to call Java functions from JavaScript and to call JavaScript functions from Java (a.k.a Reverse Ajax)."
Read this :

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Snake ! 0.2-alpha-0.1

by Jerome Kehrli

Posted on Tuesday Feb 23, 2010 at 11:40PM in OpenGL

Snake is a little C++/OpenGL project which shows a snake eating apples on a two dimensional board. It really is very much like the famous Nokia phone game except the snake finds its way on its own.

No nice textures, no sweet drawings yet. The world elements are mostly simple spheres. Trivial OpenGL features such as fog, lightning and shadows are implemented though.
Oh, and the snake it quite stupid at the moment. I wrote the path finding algorithm in an hour or so and I really need to come up with something smarter.

Snake screenshot

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hibernate's [not-found="ignore"] is buggy as hell

by Jerome Kehrli

Posted on Wednesday Jan 27, 2010 at 07:52PM in Java

I'm working on a java application which makes an extensive usage of hibernate's relation mapping system. The later offers several ways to define association mapping. We mostly use many-to-one relation declarations. The problem comes from the database. It's a pre-relational, pre-transactional, legacy database running on a prehistorical IBM zSeries host. The data on this database is very often dumb or corrupted. The lack of a proper referential integrity support and the foolish design make us end up quite often following non-existent relations.

Happily, hibernate provides a semantic which allow the application not to bother when a relation is missing, just as the legacy app does. This semantic is the not-found="ignore" parameter on the relation definition.

However, the usage of this semantic resumes to open very wide the doors to oblivion.

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Nokia n900 vs. Apple iPhone 3GS vs. HTC (OOpps.. Google) Nexus One

by Jerome Kehrli

Posted on Sunday Jan 24, 2010 at 09:37PM in Geeks-up !

I'm looking for a new phone. The 3 models I found appealing are the ones mentioned in the title of this post. I'm posting here the criterions I ran through when looking at these phones and the reasons that make me choose one or the other.

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Functional programming in Haskell

by Jerome Kehrli

Posted on Sunday Jan 24, 2010 at 05:28PM in Computer Science

Functional programming addicts,

I'm following an Haskell programming course. It was a short course, though we ran pretty much completely through the book "Programming in Haskell" by Graham Hutton. My personal view on this is that Haskell is a great language which offers a concision rarely reached by other languages, even other functional ones. The book sucks though. It's follows a way too much theoretical approach which makes it quite cumbersome and not interesting at all.

I've been told though that Hutton's book is the reference for Haskell programming. On my side I really found the various tutorials I could find online much more useful than the thorough lecture of this book I've been pretty much forced to follow.

Anyway, as usual I made a nifty summary on this book, so help yourself :

Haskell summary

The summary stands on three A4 pages and should serve as a reference for those who are initiated to Haskell programming and seek for a quick programming reference.

Happy reading, HTH.

Introduction to the theory of computation

by Jerome Kehrli

Posted on Saturday Jan 23, 2010 at 11:05PM in Computer Science

I have written a quite amazing summary on the book "Introduction to the theory of computation" by Michael Sipser. It's definitely not a replacement for the book itself as it lacks the basic explanation required to understand the presented concepts. But if you have read this book and you're looking for a short summary standing on 7 A4 pages, there you have it.

The summary focuses on the most important concepts presented by the book and holds the mandatory illustrations going along the various concepts. Well there isn't much more to say about it, so if you have read that book, check out this summary. You should be pretty amazed to see that pretty much everything actually is in it ... in less than 7 pages.

It's worth to mention though that it's quite a big file (3.8 Mb).

Summary Theoretical Computer Science

Good reading, HTH


by Jerome Kehrli

Posted on Saturday Jan 23, 2010 at 10:39PM in General


A blog about Computer Science, Software Engineering and Disruptive Technologies. is a blog that focuses on providing insights, technical explanations, experience and lessons learned on various technologies, computer sciences in general or software engineering practices.

My name is Jerome Kehrli. I have 15 years of experience in the Software Engineering Business, specialized in architecture of Information System at all levels and latest technologies and trends in Computer Sciences.
My latest interests are related to the blockchain technology and software development practices such as XP, Agile methodologies, DevOps, Lean Startup, etc.

I focus also a lot on Big Data Architecture and related technologies deployments such as NoSQL Databases, Hadoop or Spark clusters as well as machine learning and the latest trends in the field.

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