Atif Khan’s Blog

I have been a linux user since early days. In fact for home use I only have Linux and Mac OSX. I have used RedHat, Fedora and Mandrake/Mandriva in the past. Then I discovered Ubuntu few years back and it’s been no looking back. I have used both Ubuntu and Kubuntu extensively. But my destop of choice for home computer has been Kubuntu as I have alwyas felt that KDE has better tooling than GNOME. I like the simplicity of GNOME, but KDE always had more applications.

• It’s horribly slow compared to 3.x versions.
• It takes more memory to run. In fact it pretty much takes same memory as you would require for Windows XP.
• The Desktop is ugly. I am pretty happy some simple icons on the desktop. I don’t need fancy effects. There is a value in simplicty and I wish KDE devleopers learnt this from Mac OSX.
• I have been using Superkaramba for a long time and love it compared to KDE applets. In version 4, these are replaced by widgets. It just seems like a step in wrong direction as it has fewer widgets and they are horrible.
• Every time I tried to customize the desktop and L&F, it ended up screwing up everything.
• The main KDE menu is almost unusable. I don’t understand how it is more user friendly
• Same applies to Dolphin file manager. I have Dolphin on KDE 3.x as well, but again there isn’t anything mind blowing.

The release of Ubuntu 8.10 is almost here and Kubuntu is going to make KDE 4 as the default desktop. I am seriously considering switching to GNOME or Xfce going forward. The purpose of a desktop is make the life easier for a user and that has not been my impression of KDE 4. May be GNOME was right all along in the philosophy of keeping things simple and usable.

The new and upcoming Apache CXF framework is quickly gaining steam and rightfully so. It’s very intuitive, simple to use and functional. Some of it comes from the fact the its roots are in popular XFire and Celtix frameworks. It’s still in the incubation stage at Apache but the current releases are pretty stable. The documentation is not complete right now, but it’s improving as well.

One of the cases where I found the document and example lacking is the POX (Plain Old XML) service using JAX-WS Provider model and configuring it using Spring. The examples are mainly focussed towards configuring and starting the service from Java code. So, I created this simple EchoService example that shows step by step how to do it.

First step is to create the service Java class that will echo the incoming XML message back to the requester. We will also annotate this class using the JAX-WS annotation to mark it as a web service provider and the message type to be the payload. So, the CXF implementation knows that it should only deliver the message payload to the service class. The CXF binding layer processes any binding level wrappers and headers.

In the above class we specified that we want to receive the incoming XML message as DOM. You can change it to use any concrete subclass of the Source interface (e.g. SAXSource).

Next step is to create the Spring configuration. For simplicity sake, let’s keep the name of this file to applicationContext.xml. Here is an example:

The key things to notice in the above XML are:

• Address of the service (/echo).
• Binding URI (http://www.w3.org/2004/08/wsdl/http). This is really important. This is what tells CXF that this service is going to be simple XML over HTTP.
• Declaration of service factor where we indicate that the messages are going to be of wrapped nature

All that’s remaining is to declare the Spring context listener in your web.xml for the web application that this service is going to be a part of. Here is an example of the web.xml:

As you can see that there is nothing special here at all. It’s all standard Spring configuration using the context loader listener. Also, we are declaring the CXF servlet here and mapping it to /* to make all the requests to this web application go through the CXF servlet.

Now all you have to do is to package this web application and deploy it in your favorite application server. You should be able to access the Echo Service we wrote at http://localhost:8080/AppName/echo (you will have to adjust the port and application name in the URL). Now HTTP post a XML to this URL and you should get the request echoed back to you.

Maven POM
I think it’s more useful to also specify the Maven POM that contains all the dependencies as well to build the run this example. Please keep in mind that some of the dependencies here may not be required anymore as I was playing around with a lot of CXF functionalities.

Here is a list of all the jar files that ended up being in the war file from the build using above Maven POM. Again, some of the jars here may not be needed.

Sometime back I proposed a reversible enum pattern in my post. One thing missing from that implementation was the ability to successfully lookup the enum constants in cases where enum constants can have multiple values. To accomplish this, I utilized another feature introduced in Java 5, namely varargs or variable argument support. This way while building the key for the map, we utilize all the values for a constant and use the varargs in the reverse() method of the enum.

Let’s look at the interface MultiValueReversibleEnum that denotes an enum as reversible and that an enum should implement.

The things to notice in this interface are:

• getAllCode() method - It returns an array of all the possible values for an enum constant
• reverse( E ... code ) method - You can see the usage of varargs here. You basically give all the possible values for the enum constant you want to lookup in the right order

As you can see, the getAllCodes() defined in the interface is used to build the key for the map. Also, the get( final K ... enumValues ) method that looks up the value in map uses varargs.

If you run this class, you should see following getting printed:

Reverse for [1, 11]: ONE
Reverse for [2, 22]: TWO

It’s all very simple and straightforward. If you have any suggestions or feedback to improve this, please leave me a comment.

I have been spending time on and off looking at various web frameworks available for a little more than a year. A lot of this has to do with keeping track of what’s going on in the web framework arena and keep in sync with the technologies. Another focus of mine is to see how the new (at least for me) frameworks affect the productivity of a developer.

I first looked at RIFE last year and I have been very impressed by the concepts.The developers of RIFE, Geert Bevin and others have been very helpful when I had some questions. I was even able to get answers on the IRC channel for RIFE. It was not until recently that I tried to write an application using RIFE that I really got a feel of it.

Pros

• A complete framework. It includes basic web framework, ORM, Content Management, Validations, Templates etc.
• Good support from developers
• A nice quick start application to get you running quickly
• Good support for constraints for adding validations
• Continuations - ability to pause, rewind, jump through transaction steps

Cons

• Templates are really weird to work with. The syntax for the templates really did me. It is not really designer friendly like Tapestry or Wicket
• The concept of flowlink and datalink is just too verbose and not clear
• Using annotation didn’t do me any good as well for defining the flow and data links. There isn’t enough documentation for annotations
• The only way for form validations I could find was to define the a MetaData class equivalent to the domain object representing the form and define the validations in there. This just seems like way too much of work for simple validations.
• I could not figure out how to customize the error messages for form validations

In the end, I feel that it’s the lack of documentation that prevented me from really exploring it. I know Geert is a very sharp guy and if he ever gets to read my blog, I welcome his comments. I think the learning curve is too much for RIFE and lack of documentation adds to it and I am not sure if the return is proportional to the effort compared to other frameworks.

Have you ever been in a situation where you wanted to write a simple application for internal use that should be portable and completely self contained (including the database)? I am pretty sure you have. I had to do this recently for one of the simple reporting applications and I didn’t really want to create a dependency on external database like MySQL or PostgreSQL. This application needed only 4 tables and the data in these table is never going to be large enough to warrant an extensive database system. I thought about putting the data in flat files and write the code to access it. But, then I found this really neat gem called KirbyBase that does exactly the same and little more.

• Pure Ruby code
• Data is kept in simple delimited files, allowing the modification in any text editor
• It’s not an in-memory DB. The data is actually stored on the disk
• Allows various data types like String, Integer, Float, Boolean, Time, Date, DateTime, Memo, Blob, and YAML
• Allows creating indexes on fields
• Query results can be sorted
• Allows to define one-many links between tables similar to joins in RDBMS
• The columns can be defined with a formula, so the value will be calculated during insertion
• Automatic lookup fields can be defined to lookup the related values from another table

To give a simple example on how all this works, let’s consider a scenario of Department and Employees. The simple requirements can be laid out as each employee has personal information and belongs to a department. Also, each department has a name and identifier and can contain multiple employees. Following is how the code going to look using KirbyBase. Please keep in mind that I have tried to write a reusable DAO, hence the code may look a little verbose. You can very well short circuit the whole thing and write very concise code.

The output after execution will look like this:

Employee in IT department
Doe
John

Employee in IT department
John
Doe

This should also generate 2 files in your current directory, department.tbl and employee.tbl. Let’s look at content of these files now.

department.tbl

000001|000000|Department|recno:Integer|dept_name:String:Key->true:Index->1|employee:ResultSet:Link_many->recno=employee.dept_id
1|IT|kb_nil

employee.tbl

000002|000000|Employee|recno:Integer|dept_id:Integer:Key->true:Index->1|name:String:Key->true:Index->1
1|1|John
2|1|Doe

That’s all there to it. It is very powerful and easy to work with library.