一个Wicket验证示例
Java文件：

add(new RequiredMaxLengthTextField("name", new PropertyModel<String>(getData(), "name")).add(new AbstractValidator<String>() {      @Override      protected void onValidate(IValidatable<String> validatable)      {        final String groupname = validatable.getValue();        if (groupname == null) {          return;        }        getData().setName(groupname);        if (groupDao.doesGroupnameAlreadyExist(getData()) == true) {          error(validatable);        }      }      @Override      protected String resourceKey()      {        return "group.error.groupnameAlreadyExists";      }    }));

I18nResources.properties文件：

group.error.groupnameAlreadyExists=Group name already exists.