I just took a look at the documentation at http://code.google.com/webtoolkit/doc/latest/DevGuideLogging.html and it seems like FileHandler is not supported . There is a line in the documentation that seems to indicate this:
The following classes are not emulated at all: ErrorManager and LoggingPermission (not currently an issue in client logging) FileHandler -- You received this message because you are subscribed to the Google Groups "Google Web Toolkit" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/google-web-toolkit?hl=en.
