QueryWrapper queryWrapper = new QueryWrapper<>();
queryWrapper.lambda().eq(BizMainTemplate::getDeviceType, bizMainTemplateParam.getDeviceType());
queryWrapper.lambda().eq(BizMainTemplate::getMainLevel, bizMainTemplateParam.getMainLevel());
queryWrapper.lambda().eq(BizMainTemplate::getTemplateStatus, bizMainTemplateParam.getTemplateStatus());
//如果查到了就抛出异常
if ( ? ) {
throw new ServiceException(BizMainTemplateExceptionEnum.HAS_EXIST);
}else{.....}
你查询db,难道没个结果嘛?