configuration.java

@Override
public boolean configure(StaplerRequest req, JSONObject formData) throws FormException {
// To persist global configuration information,
// set that to properties and call save().
useFrench = formData.getBoolean("useFrench");
// ^Can also use req.bindJSON(this, formData);
//(easier when there are many fields; need set* methods for this, like setUseFrench)
save();
return super.configure(req,formData);
}