• Post Reply Bookmark Topic Watch Topic
  • New Topic
programming forums Java Mobile Certification Databases Caching Books Engineering Micro Controllers OS Languages Paradigms IDEs Build Tools Frameworks Application Servers Open Source This Site Careers Other Pie Elite all forums
this forum made possible by our volunteer staff, including ...
Marshals:
  • Campbell Ritchie
  • Jeanne Boyarsky
  • Ron McLeod
  • Paul Clapham
  • Liutauras Vilda
Sheriffs:
  • paul wheaton
  • Rob Spoor
  • Devaka Cooray
Saloon Keepers:
  • Stephan van Hulst
  • Tim Holloway
  • Carey Brown
  • Frits Walraven
  • Tim Moores
Bartenders:
  • Mikalai Zaikin

JSF Dynamic Select Value Error

 
Ranch Hand
Posts: 46
  • Mark post as helpful
  • send pies
    Number of slices to send:
    Optional 'thank-you' note:
  • Quote
  • Report post to moderator
Hi,

I'm facing the famous issue of the value error on Dynamic populated Select Items on JSF, the issue is that JSF requires the model to have the selected value on the UI level while this is not valid since the values are not populated on the constructor (fixed) value on the backbean level, so is there a known fix (walk-around) for this behavior.

Thanks.
 
Saloon Keeper
Posts: 27752
196
Android Eclipse IDE Tomcat Server Redhat Java Linux
  • Mark post as helpful
  • send pies
    Number of slices to send:
    Optional 'thank-you' note:
  • Quote
  • Report post to moderator
If your environment is fairly up-to-date, you can do a "@PostConstruct" method to build the resource after construction has completed.

Failing that, leave the resource NULL initially, then in your "get" method, check for null and call a method to initialize it if it is null.
 
Mohammad Jaber
Ranch Hand
Posts: 46
  • Mark post as helpful
  • send pies
    Number of slices to send:
    Optional 'thank-you' note:
  • Quote
  • Report post to moderator
Thanks for your reply, but im not sure you got my question right.

The case is that a select items is being populated using ajax , and that list is populated through the "get" method, but when the user selects a value from that list; JSF requires you to have that selected value on the back model, which may does not conatin it.
 
Tim Holloway
Saloon Keeper
Posts: 27752
196
Android Eclipse IDE Tomcat Server Redhat Java Linux
  • Mark post as helpful
  • send pies
    Number of slices to send:
    Optional 'thank-you' note:
  • Quote
  • Report post to moderator
OK, let me try again. This time I'm understanding you to mean that you haven't yet set the value of the selectOneMenu and it's still null. And you are asking what the consequences are with the selection list?

The answer is that the control should display with the first element in the selection list selected, but the backing value will remain null until the form is actually posted. At that point the selected item in the list will be used to set the value in the backing bean.

You can also allow for a "no selection" selection. I often do this, where I add an extra selection element to the top of the display list whose data value is "" and whose display value is something like "-------" or "(Please make a selection)".

Incidentally, if you have a selection whose data value is an empty string, you can force the user to make a selection by setting 'required="true"' on the selectOneMenu element. Validators don't work when no value is supplied, but "required=" takes over for that particular case. Not entirely intuitive, but at least it's consistent.
 
Mohammad Jaber
Ranch Hand
Posts: 46
  • Mark post as helpful
  • send pies
    Number of slices to send:
    Optional 'thank-you' note:
  • Quote
  • Report post to moderator
sorry again that was not the case,

any way the following link gives better understading of the issue desc.

https://coderanch.com/t/214469/JSF/java/Dynamic-Select-List-Validation-Error
 
Tim Holloway
Saloon Keeper
Posts: 27752
196
Android Eclipse IDE Tomcat Server Redhat Java Linux
  • Mark post as helpful
  • send pies
    Number of slices to send:
    Optional 'thank-you' note:
  • Quote
  • Report post to moderator
OK, in that particular case, I'm afraid my response is going to be ....

Never mind. SelectOneMenu is EXACTLY what its name says Select One Menu.

If you remove the selected item from the menu, then you are obliged to change the selection to an item that is on the menu. The whole point of SelectOneMenu is that it restricts the values to a specified list.

Thus, if you modify the list, you need to modify the selection value as well to conform to the list. Since the only way to update the displayed dropdown list is to re-render the dropdown list control, the change to the selected value should have been carried along as part of the re-rendering process.
 
Consider Paul's rocket mass heater.
reply
    Bookmark Topic Watch Topic
  • New Topic