Defining and reusing an EL variable in JSF page

jsf jsf-2 el
bertie picture bertie · Jun 22, 2011 · Viewed 87.9k times · Source

Is it possible to define variable and reuse the variable later in EL expressions ?

For example :

<h:inputText 
   value="#{myBean.data.something.very.long}"
   rendered="#{myBean.data.something.very.long.showing}"
/>

What i have in mind is something like :

<!-- 
     somehow define a variable here like : 
     myVar = #{myBean.data.something.very.long} 
-->
<h:inputText 
   value="#{myVar}"
   rendered="#{myVar.showing}"
/>

Any ideas ? Thank you !

Answer

BalusC picture BalusC · Jun 22, 2011

You can use <c:set> for this:

<c:set var="myVar" value="#{myBean.data.something.very.long}" scope="request" />

This EL expression will then be evaluated once and stored in the request scope. Note that this works only when the value is available during view build time. If that's not the case, then you'd need to remove the scope attribtue so that it becomes a true "alias":

<c:set var="myVar" value="#{myBean.data.something.very.long}" />

Note thus that this does not cache the evaluated value in the request scope! It will be re-evaluated everytime.

Do NOT use <ui:param>. When not used in order to pass a parameter to the template as defined in <ui:composition> or <ui:decorate>, and thus in essence abusing it, then the behavior is unspecified and in fact it would be a bug in the JSF implementation being used if it were possible. This should never be relied upon. See also JSTL in JSF2 Facelets... makes sense?

Related questions

Concatenating strings within EL expression defined in an attribute of a facelets tag

I need to write an EL expression for an attribute which goes something like this: #{cc.attrs.appreciatedByCurrentUser ? (cc.attrs.count +'<br/>'+ (cc.attrs.count-1)) : ((cc.attrs.count+1) +'<br/>'+ cc.attrs.count)} …

Read More
how to debug JSF/EL

How to debug EL in the JSF page? I'd like to watch variable values, function calls an so on. The best solution would be an eclipse plugin, but any other possibility is better than guessing "Why this expression failed to …

Read More
How to create a custom EL function to invoke a static method?

Im new to JSF 2. My question is related to BalusC's answer to this question jsf2 ajax update parts based on request parameters I tried the kickstart code BalusC posted and I encountered an EL parsing error: /nameofpage.xhtml @12,64 rendered="#{bean.…

Read More