问题
I'm trying to use a conditional expression in an el expression used in jsf, but it does not work.
<h:outputText value="#{(sel.description !=null) && (sel.description !='') ? sel.description : 'Empty description'} - "/>
but it does not work, the compiler says:
Error Traced[line: 118] The entity name must immediately follow the '&' in the entity reference.
Do you have any suggestions? Thank you!
回答1:
You seem to be using Facelets (which is perfectly fine). It's however a XML based view technology. Everything which you write in Facelets has to be syntactically valid XML. The & is in XML a special character denoting the start of an entity like &, <, >,  , etc.
If you would like to represent the & as-is in XML, then you'd have to replace it by &.
<h:outputText value="#{(sel.description !=null) && (sel.description !='') ? sel.description : 'Empty description'} - "/>
However, that's not pretty readable, you would rather like to use the alternative EL operator and for this (see also operators in EL for an overview of all available operators in EL):
<h:outputText value="#{(sel.description !=null) and (sel.description !='') ? sel.description : 'Empty description'} - "/>
All with all, this is in turn pretty clumsy as there's a simpler empty keyword for the purpose of testing both nullness and emptiness. This can in your particular case be used as:
<h:outputText value="#{not empty sel.description ? sel.description : 'Empty description'} - "/>
or
<h:outputText value="#{!empty sel.description ? sel.description : 'Empty description'} - "/>
or
<h:outputText value="#{empty sel.description ? 'Empty description' sel.description} - "/>
回答2:
Use and instead of &&. You simply have XML syntax error.
来源：https://stackoverflow.com/questions/13359899/using-in-el-results-in-error-the-entity-name-must-immediately-follow-the