I actually used this exact same example in my book about how rtexprvalues work. If you write the setter method on your tag handler as "public void setX(boolean b)", then you have two options for using it.
(1) You can use a static string like "true" (e.g. <myTag X="true"/>) and the JSP container will automatically convert this value for you. In fact, the container will also convert strings to numbers too.
(2) You can use a rt expression (e.g. <myTag X="<%= b %>"/>)
The real difference between (1) and (2) is that the container doesn't automatically convert the values of rt expressions. Therefore, if you do use an rt expression, the result of evaluating it must be of the same type as that declared in your setter method. This means, with your example, that you can't use <%= s %> as it evaluates to a string value which cannot be cast to a boolean.
The rule to remember here is that automatic conversion only happens for non-rt values.
Hope that helps.
Simon
[ December 12, 2002: Message edited by: Simon Brown ]
