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Vaadin is a Rapid Application Development (RAD) framework for RIA applications. I only know it for a few months but since I started experimenting with it, I'm really in favor of it. I see a lot of advantages compared to Sun's Java EE standard front-end framework JSF. First of all Vaadin is a java library, so you only have to write Java to build a complete frontend. No need for a specific frontend language, no need for converters (for comboboxes),… This also implies that you can use the full Java power on the frontend side and that's an huge advantage because frontend code is now type-safe and easily refactorable. You can unit test your frontend with JUnit. You can also use all existing java libraries on the frontend side, for example LOG4J. Another advantage is the fact that Vaadin is easy to learn (JSF isn't!) and to use: it's straigtforward. It feels like developing desktop apps and for me developing desktop apps feels much more intuitive than developing web-apps the way I'm used to. Vaadin uses convention over configuration. No need to register new components, validators or whatever in different xml files. Themes have a default folder and a default folder structure. Vaadin is very well documented. There's the book of Vaadin wich explains every aspect of the framework very clear. On the site there's a blog, a FAQ section, a wiki, a forum, examples with Java source code, … It's very easy to extend. Want to create your own Validator? Just implement an interface or extend another Validator and use it. Want to create your own custom server side component? Just extend the CustomComponent class or extend from another component. There's also an add-on directory where you can download UI components, data components, tools, themes, …

"I've had an opportunity recently to work on a product that needed an RIA web interface, and I chose my recent favorite tool for this, Vaadin. The services for this project needed to be highly scalable, and lent themselves well to functional techniques, so I selected Scala as my language of choice. I build my projects with Maven, for reasons I won't go into right now, and I do much of my JVM-language work in Intellij's excellent IDEA IDE. Given these tools, I found a way to facilitate very rapid development of web UI's, and I thought I'd pass it along. Another technique I use, which I'll expound on later, is creating "dummy" implementations of all of my backing services for my application. The "real" implementations are written as OSGi services, in separate modules from my UI. The UI is packaged as a war, but is also OSGi aware, with a bundle activator. This activator only gets called if the war is deployed into an OSGi container, and not otherwise. This allows the app to select which implementation of the services it uses - the "dummy" ones when it's deployed outside of OSGi, and the "real" ones when they're available. This means I can use the handy Maven jetty plugin to quickly spin up my application and test it on my local workstation, without needing all of the dependencies (like a data store and such) of my real services. That's good, in that I can get my "cycle time" down to a few seconds, where "cycle time" is the time between making a change and actually being able to test it in my browser. We can do better, though. I'm using Scala as my language of choice for building the UI as well, as it works just fine with Vaadin (and with everything else in the JVM ecosystem, for that matter, which is why I didn't choose a non-JVM language - but that's yet another rant). I compile my Scala with the Maven scala plugin - here's where the next handy bit comes into play. Turns out the Scala plugin has a goal cal

""Coming from desktop application development, I have found the IT Mill Toolkit [Vaadin] to be a lot of help in the transition to web application development. With the toolkit, writing AJAX enabled web applications is as easy as writing Swing based GUI code. It hides so many frustrating details, and handles browser independence so I don't have to worry about it. Using the toolkit makes it quite easy for me to write sophisticated web applications." Bo Thorsen, Monty Program AB"