Dynamic key name for labels

[chawax]

Hi,

I use the Seam messages component but I need the key to be dynamically generated.

For example I want my label keys to start with label. then concatenate a value coming from an iteration.

I tried this :

<ui:repeat value="#{task.transitions}" var="transition">
     <s:button value="#{messages['label.#{transition}']}" 
     action="..."  />
</ui:repeat>

But it doesn't work. Anyone know if it possible thanks to Seam EL enhancements ?

[damianharvey.damianharvey.gmail.com]

You can't specify an expression inside an expression like that. You might want to lookup concentenate JSF functions to combine 'label.' with transition to pass into messages. There was a thread about this last week I think (search for concatenate).

Or you could always override the  org.jboss.seam.international.Messages class (where #{messages} comes from) and put your label. in there. Usage would then be something like

<s:button value="#{mymessages[transition]}" />

Cheers,

Damian.

[chawax]

Thanks Damian for your response.
I like your suggestion of overriding the Messages class. Unfortunately the label. prefix was just an example and most of the time I have no idea what the prefix will be.

Anyway I created a Seam component to solve my problem.

@Name("messageUtils")
@Scope(ScopeType.STATELESS)
public class MessageUtils {

     public String getDynamicMessage(String prefix, String key) {
          StringBuffer sb = new StringBuffer();
          sb.append(prefix);
          sb.append(key);
          return SeamResourceBundle.getBundle().getString(sb.toString());
     }
}

Then I can use it this way :

<ui:repeat value="#{task.transitions}" var="transition">
    <s:button 
        value="#{messageUtils.getDynamicMessage('label.demandeAbsence.', transition)}" 
     action="#{validationDemandesAbsenceAction.choisirTransitionTache(task.idTache, transition)}"  />
</ui:repeat>

Best regards,

Olivier

[damianharvey.damianharvey.gmail.com]

No worries. You should probably throw an @BypassInterceptors on that class as well. For usage like this it improves performance (there's a long long thread on it somewhere in this forum).

And if you're well keen, then apparently EL functions are more performant that using a Bean in this manner (although I use them the same way as this without any trouble).

Cheers,

Damian.

[chawax]

Thanks for the tip about @BypassInterceptors.

About EL functions, will it be possible to use Seam built-in components if the class containing the EL functions is not itself a Seam component ? And then I can't see the difference between EL functions and Seam components. I had posted a JIRA about the ability to extend the list of EL functions supporters by Seam EL resolver a few months ago, don't know if it has been token in account.

By the way, I have another strange problem with dynamic EL expressions. The transition variable is known when using my messageUtils component. But when I use my other component on action attribute of my s:button, the transition variable is an empty string !

Can't understand why since there is no problem with task.idTache parameter and both methods consider transition parameter as a String ... Do you have any idea where it could come from ?

[tom_goring]

EL functions are static methods on simple class (non-seam component).

But you can pass on the request to a seam component however....

e.g.

     public static String descriptionForOptionList(String listKey, String value) {
          UserPreferencesBean bean = (UserPreferencesBean)Component.getInstance(UserPreferencesBean.class, ScopeType.SESSION);

          return bean.descriptionForOptionList(listKey, value);
          
     }