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

Question

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)} 

Now the problem is that this gives an error as strings cannot be concatenated, the way I am doing it. So how can I rectify this?

I'm using JSF 2.0 with facelets.

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EDIT :

I'm resolving the issue using the following inline javascript

            <script type="text/javascript">                 var count=#{cc.attrs.count};                 document.write(#{cc.attrs.appreciatedByCurrentUser} ? (count-1) +'<br/>'+count  : count+'<br/>'+ (count+1));             </script> 

Can you think of any issue with this?

Answer 1

It is possible to concatenate Strings in EL using the java.lang.String.concat(String) method. Thus your code could look like:

<h:outputText value="#{cc.attrs.appreciatedByCurrentUser ?  (''.concat(cc.attrs.count).concat('&lt;br/&gt;').concat(cc.attrs.count-1)) :  (''.concat((cc.attrs.count+1)).concat('&lt;br/&gt;').concat(cc.attrs.count))}" escape="false" /> 

In this particular case however I would go with one of the options that Mr BalusC had suggested because the code above doesn't look quite elegant. In some cases knowing this technique could be useful, though.

I would hardly recommend using javascript as a workaround here.

Answer 2

String concatenation in EL is only possible by just inlining in the expression. The + operator is in EL exclusively a sum operator. Further, < and > are invalid characters in XML attributes, so you have to escape them (and instruct <h:outputText> to not escape them once again by escape="false"):

<h:outputText value="#{cc.attrs.count}&lt;br/&gt;#{cc.attrs.count-1}" escape="false" rendered="#{cc.attrs.appreciatedByCurrentUser}" /> <h:outputText value="#{cc.attrs.count+1}&lt;br/&gt;#{cc.attrs.count}" escape="false" rendered="#{!cc.attrs.appreciatedByCurrentUser}" /> 

Alternatively, you can also use <c:set> to alias the expression:

<c:set var="appreciated" value="#{cc.attrs.count}&lt;br/&gt;#{cc.attrs.count-1}" /> <c:set var="notAppreciated" value="#{cc.attrs.count+1}&lt;br/&gt;#{cc.attrs.count}" /> <h:outputText value="#{cc.attrs.appreciatedByCurrentUser ? appreciated : notAppreciated}" escape="false" />