String Concatenation in EL [duplicate]

With EL 2 you can do the following:

#{'this'.concat(' is').concat(' a').concat(' test!')}

This answer is obsolete. Technology has moved on. Unless you're working with legacy systems see Joel's answer.

There is no string concatenation operator in EL. If you don't need the concatenated string to pass into some other operation, just put these expressions next to each other:

${value}${(empty value)? 'none' : ' enabled'}

If you're already on EL 3.0 (Java EE 7; WildFly, Tomcat 8, GlassFish 4, etc), then you could use the new += operator for this:

<c:out value="${empty value ? 'none' : value += ' enabled'}" />

If you're however not on EL 3.0 yet, and the value is a genuine java.lang.String instance (and thus not e.g. java.lang.Long), then use EL 2.2 (Java EE 7; JBoss AS 6/7, Tomcat 7, GlassFish 3, etc) capability of invoking direct methods with arguments, which you then apply on String#concat():

<c:out value="${empty value ? 'none' : value.concat(' enabled')}" />

Or if you're even not on EL 2.2 yet, then use JSTL <c:set> to create a new EL variable with the concatenated values just inlined in value:

<c:set var="enabled" value="${value} enabled" /><c:out value="${empty value ? 'none' : enabled}" />