I´m soon to start a new mobile app project and I dont have that much experience with either iOS or Android development but I have used Vaadin for presentation tier on different occasions. The app will most likely be lightweight for the mobile client but more heavy for backend servers(jboss). I feel kinda lost so i´m asking you.
Question: What are the drawbacks of using Vaadin touchkit compared to other frameworks/ build from scratch? Where might a problem occur? Any input and recommendations are welcome!
I am currently developing a small application using Vaadin TouchKit that once it enters production will have some hundreds of users. I haven't been able to locate any publicly available apps in production that have been implemented using Vaadin Touchkit, so what I'm going to list here is based solely on my personal experience with the technology.
Drawbacks compared to native applications:
I'm assuming this is what you refer by "building from scratch".
As this is web techonology, your application performance will always correlate heavily with the quality of the users Internet connection. If you have to render large UI's with a lot of components and details, it will be slower than doing so in a native application. A lot slower if the users connection is poor. Or if a connection is unavailable, then your application pretty much becomes unavailable. There is a way to use HTML5-cache for providing an offline-mode in a Vaadin Touchkit app, but it is not very useful for storing large datasets as the cache has a lot more limitations than for example an Android SQLite database. For simple UI-stuff it might be viable, but storing data for offline-access is in my opinion pretty much out of the question.
Other than the above mentioned points, I have not run into any missing capability, as you can use any Java library at any time on the server-side, and your application will be running safely in a servlet container.
Upsides compared to native applications:
You didn't spesifically ask for the upsides, but I guess this is any input and recommendations.
Your Vaadin Touchkit app can run on basically any mid-high tier mobile device launched after 2010, basically excluding only the ones with Windows Phone OS, since Internet Explorer does not use WebKit for rendering and other browsers are not available as far as I know. And since this is a web application, it does not exclude any other desktop browsers than Internet Explorer. By creating one application, you support roughly 80-95% of your users.
As mentioned, any Java library, any internal API, any authentication method supported by your hosting environment is available to your app, which is not as easy to implement for native mobile applications. This can be overcome with great software engineering, but demands a significantly higher amount of developer resources, not to mention that you are still stuck doing it for each platform separately.
And of course maintenance of a servlet app compared to the maintenance of a native application is considerably more simple: deploy once, all users get the changes without doing anything. No app store, no versioning, no hassle.
Vaadin TouchKit compared to other web development:
I am not familiar, at all, with web application development without using Vaadin, so I am not going to tell you whether or not it is the way to go compared to other modern web application technologies and frameworks. All I'll say is that in my experience Vaadin makes creating UI's and backend functionality relevantly easy and more graspable if you are familiar with Java development and desktop application development in general.
To conclude, don't rush in to create your mission critical application using Vaadin TouchKit before at least prototyping with it, and getting to know the performance and limitations it presents. For certain type of applications, it might be one of the best solutions. For a certain, larger group than the other, it is probably one of the worst. It is not a very mature or generally adopted framework, but it is useful. I'll be happy to hear more about the type of app you're planning and help you figure out if there are any showstoppers for using Vaadin TouchKit.
P.S. You've probably already run into this, but this document opens up the guts of one of the TouchKit demo apps:
http://demo.vaadin.com/vornitologist/VAADIN/tutorial/touchkit-tutorial.html