Head First Servlets and JSP, 2nd Edition

Set a default value with the default attribute

Suppose you want to show these anonymous users a message that says, “Hello guest.” This is a perfect place to use a default value with the c:out tag. Just add a default attribute, and provide the value you want to print if your expression evaluates to null:

Or you can do it this way:

<b>Hello <c:out value='${user}'>guest</c:out></b>