But what I want to talk about today is something pretty simple: Internet Explorer and column widths. We’ve written a custom component which replaces Smart GWT’s ListGrid – essentially it uses a standard HTML table instead of using DIVs.

Part of the issue we were having is that the column widths were essentially being ignored: IE was just drawing all the columns as equal width. (The CSS on the TABLE element was set as table-layout: fixed).

We were using the HTML COL tag to set the width for each column – all this was added in dynamically via GWT.

As it turns out, the reason IE was ignoring this was because you need to add it to a COLGROUP first. If you add in a COLGROUP, and then add the COL elements to that group, it works.

By that I mean, each module has its own message source, but you want them to be combined into one MessageSource. This could be required for various different reasons which I won’t go into here, but suffice it to say that this is possible with Spring.

I created an AggregatingMessageSource which would scan the ApplicationContext for instances of MessageSource. When a message was requested, it would search each one sequentially for the relevant message.

Anyway, if you need such a class, I have uploaded it to get you started. Obviously, customise it to your own needs: AggregatingMessageSource.java.

It’s been going pretty well so far, although I’ve only been working on it for a few days. I’ve got the GWT-Widget server library up and running as well, which integrates nicely with Spring for RPC. (It basically means you don’t have to define a new servlet in web.xml for each RPC server you want, you can just define them as Spring beans).

However, it does mean that you have to create a mapping for each Spring bean that you want to publish and define it in the application context XML, which isn’t really ideal for modular applications: I’d quite like them to be detected automatically with annotations, that way if you have another module on the classpath it will automatically be picked up.

So, I created another annotation (@RPCService) and annotated my RPC endpoints with it. The annotation, as its value, had the URL of that endpoint (i.e. “/user” for the users RPC service)

Then, my initial thought was to use Spring to scan the classpath and load each one up. I’ll cut a long story short here and say that was all unecessary: if your RPC classes are defined in the application context (via XML or annotations, it doesn’t matter), all you need to do is get an instance of the Application Context and call getBeansWithAnnotation.

This makes things really simple: I have a bean set up which has an initialise method that uses that method to get all classes annotated with my RPCService annotation, finds out their URLs, and then configures the GWTHandler servlet to map those beans.

Dead easy! And very useful to do, if you’re using the GWT-Widgets library.

Edit: After reading the documentation it seems that what I’ve done is essentially re-implement what’s already available in the library. Still, hopefully it will come in useful if you need to do something similar for another usage…

java.lang.IllegalArgumentException: argument type mismatch

Anyway, I found an answer which seems to work, but rather than post it directly here I’ll simply link to the original question on StackOverflow (in case someone posts a better answer subsequently!).

These kind of issues are one of the many reasons why JSF has gone down in my estimation… it’s not a bad framework, it just seems to make what should be simple things massively complicated! That said, JSF 2.0 looks good, so maybe it will solve these kind of issues.

I won’t bore you with the details, but I do want to blog about the way C# is used in SSIS. You can create ‘Script Tasks’ which basically run a piece of code for you. You can write it in VB.NET or C#.

Due to the particular export I was running, a lot of the logic needed to go into the C# code. The issue is, SSIS doesn’t make it easy for you to re-use code: essentially, when you create a script task you are creating a whole new C# project. This isn’t good.

What I did (after taking some advice from Stack Overflow), is create a class library. Being new to SSIS and the world of C# in general, I had to do a fair bit of trial and error to get it working. The best tutorial I found was here. Those steps were enough to get me started.

There are a few other things to mention as well:

• For some reason, SSIS 2008 seems to be stuck in the world of .NET 2.0. I don’t know why, but that is why you have to copy the .dll to the .NET 2.x folder. You will probably also need to set the project properties (of your class library project) to .NET 2.0.
• There seem to be two different ways of accessing SSIS variables from within a script, depending on whether your script is part of a Data Flow Task or not. If it’s part of a Data Flow Task, you access them via the ‘Variables’ member – easy enough. (Although remember to set them up as read-only or read-write variables in the task properties first). If your script task isn’t part of a data flow task, you will need to use the Dts variable. This confused me at first!
• For some reason, rebuilding the Class Library package in Visual Studio seems to mean the Script Tasks using it also need to be recompiled. Update: I’ve found out why – if the version increments, you will need to rebuild the dependent projects. To stop this, you just need to set the class library version to be constant. This was actually the default in my project, but I’d changed it! You can do it from project properties -> Application -> Assembly Information dialog.

In general, it’s been a learning experience – worth doing though! I will hopefully update a bit more when I’ve had a chance to use it more…

I kept getting this error and it turns out it was a problem with my workspace not being in sync with the files on disk. A refresh did the trck. I don’t know why this results in a NullPointerException, but there you go!

Witness this statement of mine I wrote a month or so ago. The point of the code is to append a prefix to an existing description, or the empty string if the description is null.

description = prefix + " " + description == null ? "" : description;

Can you spot the error?

It turns out that Java was looking at this statement like this:

description = (prefix + " " + description) == null ? "" : description;

D’oh! Not what I intended! I changed the statement to put brackets round the description == null ternary statement and it seems to work.

Just goes to show, brackets are generally a good idea when making statements like this – it’s too easy to make mistakes with operator precedence otherwise!

I had an issue today whereby I needed to deploy the application on a server (it’s a web app). I kept coming up with errors about JAI not being able to find the TIFF decoder:

java.util.NoSuchElementException
     at javax.imageio.spi.FilterIterator.next(Unknown Source)

For anyone who is Googling it!

Anyway, it turns out that I had got jai_core.jar and jai_codec.jar in my WEB-INF/lib folder (these are both part of the standard JAI Distribution), but for some reason I also needed jai_imageio.jar (which is part of the JAI-ImageIO package).

I can’t quite fathom why you need so many JAR files, but it seems to work now, so there you go. Hope this helps someone else out!

My first impressions are, I like it. I like it a lot, in fact. It seems to achieve a much more clean separation between code / components and HTML than other frameworks do. It does take a while to get your head around it though – I’ve only been working with it for a few days so am still finding my way round!

But I expect I will blog up some info when I’ve got my head around it.

Anyway, I wanted to post up some of the things I’ve discovered: Swing is very easy, but it seems there aren’t many “best practice” guides for building an application using it. So, here is my list of “best practices”… hope you find it interesting!

• The Presentation Model pattern is well worth using. It creates a much more loosely coupled dependency between the GUI code and the presentation logic.
• On a similar note, using a binding framework (such as JGoodies Binding).
• Use Actions (i.e. subclass javax.swing.AbstractAction) for use with menus and buttons etc.
• For laying out forms, JGoodies Forms is awesome.
• There are benefits to using component factories, i.e. a factory method to create your different UI components such as buttons.

I think that’s about it for the moment. The only other thing is, the Spring Rich Client Project (Spring RCP) looks really interesting, and I think if I was starting a new project I’d probably use it.

What are your favourite Swing tips?