Can you provide some sample code in which some RuntimeException is thrown? It is difficult to answer your question correctly unless you tell us what your exact problem is.
As far as I can tell you, your BootStrap.groovy should look something like this:
class BootStrap {
def exceptionHandler
def init = { servletContext ->
exceptionHandler.exceptionMappings =
[ 'NoSuchFlowExecutionException' :'/my/doIt',
'java.lang.Exception' : '/error',
'org.you.YourCustomException' : '/yourErrorController/yourErrorAction' ]
}
def destroy = { }
, RuntimeExceptions .
: ?
, RuntimeExceptions ?