EDIT

import java.util.Map;

import org.apache.log4j.Logger;

import com.vaadin.data.Validator.InvalidValueException;

import com.vaadin.data.fieldgroup.FieldGroup.FieldGroupInvalidValueException;

import com.vaadin.server.AbstractErrorMessage.ContentMode;

import com.vaadin.server.ErrorMessage.ErrorLevel;

import com.vaadin.server.UserError;

import com.vaadin.ui.AbstractField;

            fieldGroup.getFields().forEach(f -> ((AbstractField)f).setValidationVisible(true));

            if(e.getCause() != null && e.getCause() instanceof FieldGroupInvalidValueException){

                FieldGroupInvalidValueException invalidValueException = (FieldGroupInvalidValueException)e.getCause();

                updateFieldNotifications(invalidValueException.getInvalidFields());

                Notification.show("The entered data in " + invalidValueException.getInvalidFields().size() + " fields is incomplete or invalid.");

            } else {

                Logger.getLogger(this.getClass()).error("Error saving", e);

                Notification.show("Error saving", Type.ERROR_MESSAGE);

            }

    /**

     * @param invalidFields

     */

    private void updateFieldNotifications(Map<Field<?>, InvalidValueException> invalidFields) {

        for(Field<?> f : invalidFields.keySet()){

            if(f instanceof AbstractField){

                String message = invalidFields.get(f).getHtmlMessage();

                ((AbstractField)f).setComponentError(new UserError(message, ContentMode.HTML, ErrorLevel.ERROR));

            }

        }

    }