Since MyFaces committer "Jakob Korherr" has only read-access to this list, I am forwarding this mail. -Matthias PS: we use this forwarding "work-around" instead of filing issues against the spec (for discussions). ---------- Forwarded message ---------- From: Jakob Korherr <jakob.korherr(a)gmail.com&gt; Date: Thu, Apr 8, 2010 at 2:46 PM Subject: State saving of UIViewParameter To: Matthias Wessendorf <mwessendorf(a)gmail.com&gt; Hi, Yesterday we received an issue about the state saving of an UIViewParameter in combination with an AJAX request on the MyFaces user list (see [1] for details). This opened some questions/problems: UIViewParameter uses the submittedValue to store its value in the state for the next postback, because obviously the view parameter won't be in the request parameter map of the next request (which is the postback). But because its submittedValue is null after the conversions and validations, it has to be set again before the state is generated. To accomplish that, the spec currently states to override encodeAll() and make the call to setSubmittedValue() there. In addition, encodeAll() has to be called in UIViewRoot.encodeEnd() for every UIViewParameter in the view. This works perfectly for normal requests, but when you are using an AJAX request the state is generated before UIViewRoot.encodeEnd() is called an thus the submittedValue for every UIViewParameter is null in the state. This means that the value of every UIViewParameter will be null in the following request. Now the easiest solution to this problem, which I also already committed to MyFaces trunk (again see [1] for details), is to do mostly the same as in UIViewRoot.encodeEnd() just also in PartialViewContext. processPartial() when the PhaseId is RENDER_RESPONSE before the state is generated to make it work for AJAX-requests. However I don't really like this solution, because we have to think of handling UIViewParameters in a special way every time we change something on any render mechanism. Why don't we just override saveState() on UIViewParameter and set the submittedValue there before the state is saved. This will have the same result, but without the code in UIViewRoot, PartialViewContext and UIViewParameter.encodeAll() and without future headaches. I also already uploaded a patch for this to the MyFaces issue at [1]. The second thing I want to bring up here is an issue I ran into while testing the first one. Imagine you have a page with a required UIViewParameter called input. You will get a validation error as long as you don't access the view with ?input=abc. Now if you do that once, "abc" will be saved as the submittedValue in the state of the UIViewParameter for every postback and thus will be available for every further postback. If you now access the view again with a GET request (non-postback), but without ?input=abc, you will again get a validation error. However, if you hit any button or link on the view to generate another postback to the view, the validation error will be gone, because UIViewParameter takes the value from before ("abc") out of the model (managed-bean) and sets it in the state. Thus you haven't provided it via ?input=abc, but you will now have a value of "abc" for your UIViewParameter, which seems kinda wrong to me. The solution to this one is to get the value from the model to set it as the submittedValue in UIViewParameter only if the current request is a postback. However I don't know if this really is an error or the expected behaviour. I personally just think that it is weird. Many thanks for looking at this! Regards, Jakob [1] https://issues.apache.org/jira/browse/MYFACES-2645 -- Matthias Wessendorf blog: http://matthiaswessendorf.wordpress.com/ sessions: http://www.slideshare.net/mwessendorf twitter: http://twitter.com/mwessendorf