Ask a Vaadin Expert Live Webinar


Schedule and topics for Wednesday March 12th
1.00 PM CET Vaadin Expert Peter Lehto: Introduction to Vaadin
2.00 PM CET Vaadin Expert Thomas Mattsson: Integrations and Using Vaadin
3.00 PM CET Vaadin Expert Leif Åstrand: Core Vaadin

We will be following this thread during the webinar. You can comment and ask questions in realtime below.

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Hello i have few questions:
Why doesn’t Calenar use Locale from UI (as other components?) but just from system?
Why doesn’t Upload implement Field?
Is validation of not null in vaadin 7 part of validation, or it is still checked before validation? And why is used this model? It’s quite anoying.

Do you really use MVP in vaadin application user for your clients? It seeems for me quite useless if you have just one View.

Are you planning to drop support of gwt and switch client to native JS? Does GWT bring any advantages yet, when you support IE8 and above?

When are you planing to drop support of IE8?

Why don’t you change nullrepresentation from null to “” it’s quite anoying too…

There was a good question from Nagarjun about creating Vaadin Add-ons, and you can find some pointers to the topic in GWT.create workshop slides here:

how can we integrate gwt to vaadin? can gwt component be used inside vaadin container?


I am happy to use the free and excellent component: Calendar.
I think it is very similar component to a table with a itemcontainer with interval, date-pair property and has a day / week / month -paging.

It is very comfortable to implements own CalendarEventProvider, but sometimes I thinking, why it doesn’t use / implement the common Vaadin-datamodel (Property/Item/Container)? It could have own Container-type (CalendarEventContainer?).
Why CalendarEvent is not an Item?


Vaadin is great for session-oriented applications. In my case I have a (rather simple) frontend part where users can log in and a rather complicated backend. If the user is not logged I would prefer having a non-session-oriented behaviour (= no session timeout). What is the best approach for realizing this?

  • Realize everything in Vaadin and set the session timeout very high. (Gobbles up resources, doesn’t it?)
  • Use static HTML-pages for the frontend and embed a HTML form to login. (I would prefer to realize everything in Vaadin…)
  • Create the frontend as one client component. This means the server session does not start before user is logged in. (Does that work? Is there an example how to realize this?)
  • Other solutions?
    Thanks in advance

Hi Peter,

We covered some of these topics in the webinar, but here are some more ideas and answers to your questions.

With Vaadin make sure the @PreserveOnRefresh to false. This makes the application behave more like pages on reaload, but sessions are still there. If you really worried about the session and have very simple UI for these users, you could build a display with plain servlet/JSP/some page oriented framework and keep Vaadin where it is the best.

Actually session timeout is a server setting.

Right. I’s also prefer Vaadin here :slight_smile: Sounds like (premature?) optimization to try to get rid of big sessions for non-logged-in users. Vaadin itseld is not really that heavy (JSF implementation might be much heavier) - biggest performance/memory problems are most likely in the data binding / retrieval.

Session is mostly handled on server. So actually it does not help in that sense. But lightweight implementation with short session timeout makes it less heavy for server. But then again, maybe you don’t even need to worry about this yet. :slight_smile:

Hi Sami,
thanks for your reply. What I meant by “- Create the frontend as one client component. This means the server session does not start before user is logged in. (Does that work? Is there an example how to realize this?)” is, that this part would be implemented as client-side-only application (see chapter 14 in BoV). A client-side-only application has no sessions, hasn’t it ? The idea would be now that the frontend is client-side-only (= session-less) the backend session-oriented. When the user logs in server communication starts and a session would be created. For me following problems appear:

  • Is it possible to mix a client-side-only application with a “normal” application?
  • How could I combine these two?

How can i add a combobox to one particular column of a grid ?
Please help. in urgent need…