I have two dependent dropdowns on a JSF page that work fine. I use a valueChangeListener on the first dropdown that populates the List backing the second dropdown.
However when I try to submit my form it's failing JSF validation. From testing I think the problem is that when the page loads my dependent dropdown list is empty, then I populate it after the first dropdown has a selection made. However none of the values now in the dependent list were in the list when the page loaded so it's fails validation. I have confirmed this by using a constructor to set up the list with all the possible values when the page loads and it makes my problem go away however this isn't a possible solution as loading up all the values would kill the performance of my page.
Any ideas how I can get it working?
Regards,
Kevin.
This is EXACTLY the use case for a view scoped bean. Using a request scoped bean in such case is going against the grain of JSF (possible, but painful - like using a hedgehog as a bath sponge).
If there are any problems with such solutions, then tell us, there should be a way of mitigating them; the point is, you should use the view scope and solve any problems you might have with that, and not try to run away from it.
Related
If you do JSF AJAX calls and change the component tree while rerendering (or between ajax calls), you'll get exceptions from Mojarra. As I understand it, it's difficult to recreate the component tree partially when the new tree is different as the one stored in the ViewState (or the actual JSF class). That's "ok". I'm thinking about using the rendered attribute and not rendering the component.
My question: How does the rendered attribute work? Does the component get restored and is the component tree, that JSF creates during restore phase, safe? We have a very dynamic XHTML page and not rendering object's instead of disabling them with css classes would really up the speed of the page.
I tried it and it works as expected. So JSF only assumes that the component is there even if it doesn't render anything.
Please consider that the view state does get restored and it's still a performance hit (but a smaller one as nothing get's sent over the wire and the output string/html doesn't need to be rendered).
I want to enable a pair of cascading dropdown lists within a form in an ASP.NET MVC3 / Razor2 application. Ideally the solution will meet the following goals:
Child list populated simply by changing the selection of the parent list
Both dropdown lists contained within the form as they need to post information on submit
Uses Ajax to avoid whole page round-trip
Uses Ajax Html helper for easy integration
Works even if javascript is not enabled
So, from a user point of view, when an item in the parent dropdown is selected, the contents of the child dropdown is refreshed to display items related to it.
Can anyone please suggest the best way to do this?
EDIT.
No takers ... suggests to me that there may be conflicting requirements in the above list of goals. The closest I got to the above was this article, which met all the goals except that it doesn't work nested within an Html form.
So, I will restate the problem in a different way: how can I make an AJAX call from a dropdown list within an Html form so that I can populated another dropdown list with related items?
Took some time to find a reasonable solution to this, although so far I still don't have a no-jquery fallback. This article shows you how to use AjaxHelper extensions to create your own Ajax-enabled controls. Works a treat, and very reusable.
I have various tables with the following size : 12 columns and up to 1800 rows. It takes 8 seconds to render it to the user. I currently use h:dataTable. I tried ui:repeat to get the row data from a Java List object, managed by JSF. Although this works fine, the 8 seconds to render the table is unacceptable. I'm trying to find other ways to do this, but need to keep JSF as my controller for action buttons on the page. In other words I want to create the 'table markupto send to thepage myselfand then still associate actions onh:commandButtons` to the managed bean methods. Is there a way to do this?
The only ways I can think of is to use jquery or ajax to create the table markup, although I am new to technologies other than JSF for UI development.Maybe then I would somehow pass that to the client for render. The only problem is I don't know how to generate the markup from my list, and second how I would inject it between h:commandButtons that are in my XHTML file currently.
Does any one know how I can solve this without having to completely rip OFF JSF? One main problem I have is that the business requirement that says we can't page the datatable (i.e: Next / Back buttons displaying 100 at a time for example). So, possibly I was thinking I could do this by Ajax calls to the server and get 100 rows at a time after page ready, and append new rows behind the scenes to the user. This would be a "perceived" speed of load, but I don't know how to do this at all.
8 seconds isn't bad for a whopping 1800 rows on 12 columns. 10~100 rows is done in less than a second, right?
Before continuing with this, are you absolutely positive that all those 1800 rows are supposed to be shown at once? Isn't this very user unfriendly? Wouldn't the user have to need Ctrl+F to find the information it is looking for? Isn't that annoying? Why don't you introduce filtering (a search field) and pagination exactly like as Google is doing to present the zillion of results in a sane and user friendly manner?
Anyway, you could consider using "On-Demand data" option of PrimeFaces <p:dataTable>, wherein the data is loaded by ajax during scrolling via <p:dataTable liveScroll="true">. See also the showcase example. No homegrown code nor manually fiddling with jQuery necessary. PrimeFaces has done it all under the covers.
It you don't want to use PrimeFaces for some reason, then you could consider using OmniFaces <o:componentIdParam> in combination with some jQuery "live scrolling" plugin. See also the last example in its (snapshot) showcase page for a kickoff example (which should easily be adapted to be triggered by hitting the scroll bottom instead of by clicking).
I'm coming from a WebForms environment. When I wanted values from a radiobutton, the form simply got ajax reposted or I got it thru javascript.
I've searched the web, but can't seem to find an equivalent for MVC 3 Razor.
I'm not posting the form, so I can't use the FormCollection object in the ActionResult.
I simply want to get the value of which option in the RadioButton is checked when a user checks one of them.
I assume I would do this thru an Action method in a Controller once a user checks one of the values.
Note also, that this radiobutton list is in a partial view and is available to the entire website (because it is in my _Layout.cshtml view).
Can someone please help me out with what I think should be a simple task?
You need to use javascript. See this post. MVC does not have the concept of an Auto-Postback like in Webforms. This is an optimization in the page loading time (no self-managed viewstate). This means you need to manage the statefulness of controls yourself.
In short, if you're not posting (or "getting") the form then the value won't be available in the controller...more specifically, neither the controller nor it's actions will be called at all.
If you're trying to do something strictly UI related, then you may want to consider jQuery.
If you're trying to do some sort of model validation inside of the view, you may want to reconsider your approach and usage of the MVC pattern.
I'm trying to build a fairly complex form which as a couple of cascading selects - i.e. the user selects a value in one combo and the other combo is populated according to their first selection.
I've followed a tutorial on how to handle the cascading but the problem I have is that I now have nested forms (the code in the tutorial uses forms inside partial views to POST to a controller action to load the 2nd combo). I have my main form on which I want to collect the input values but also the nexted forms for the cascading select boxes. The problem I have is that the cascading selection doesn't post to the correct controller action, but instead posts to my main (outer) form's action.
I understand this is the correct behaviour for a browser (as nested forms apparently aren't supported) but what's the correct way to implement this?
The correct way is to only have one form. Then use AJAX to populate the cascading drop down list. The are 100s of examples online how to do this with JSON
use this to have multiple submit buttons on one form which each have different controller actions to post to:
http://iwayneo.blogspot.co.uk/2013/10/aspnet-mvc-action-selector-with-list.html
as for cascading stuff - i would focus on populating these without Ajax 1st - then you can worry about adding this sort of flare - if it doesn't work without JS anyway you're in a bad place.
I would have the 1st dropdown populated when you initially load the form and have a "next" button to populate the next dropdown in the cascade. this submit can use the method above to post to an action which then populates the second data set based on the selection of the 1st dropdown.
make sense?
Then how you ajax that after the point is up to you but you'll have a very solid foundation to build up stuff like that as you will have it working in the minimal tech scenario.
w://