import org.apache.wicket.markup.html.form.validation.AbstractFormValidator; //导入依赖的package包/类
@Override
public IFormValidator getFormValidator() {

    final CheckBox firstCheckBox = findFirstCheckBox();

    if (firstCheckBox != null && (minSelections > 0 || maxSelections > 0)) {

        return new AbstractFormValidator() {

            @Override
            public FormComponent<?>[] getDependentFormComponents() {
                return null;
            }

            @Override
            public void validate(Form<?> form) {

                if (!CheckBoxContainerPanel.this.isEnabled()) {
                    return;
                }

                int count = getSelectionCount();

                if (isVisibleInHierarchy() && count > maxSelections) {
                    firstCheckBox.error(maxSelectionsError.getObject());
                }

                if (isVisibleInHierarchy() && count < minSelections) {
                    firstCheckBox.error(minSelectionsError.getObject());
                }

            }
        };

    } else {
        return null;
    }

}