protected boolean onSubmit(AjaxRequestTarget target, Component contents) {
// cascade delete the whole selection
GeoserverUserDao dao = GeoserverUserDao.get();
for (User user : selection) {
if(!user.getUsername().equals("admin"))
dao.removeUser(user.getUsername());
}
try {
dao.storeUsers();
} catch (IOException e) {
e.printStackTrace();