java.lang.ClassCastException：[Ljava.lang.Object；无法转换或 BeanUtils.copyProperties 不起作用

我是 JPA 新手，并且 Spring Boot 在使用 @Query param 时无法获取 api 响应（我尝试实现内部联接）

存储库类：

 @Transactional(rollbackFor = Exception.class)
    @Modifying
    @Query("select A.id, A.position ,A.title,A.shortdescription,A.thumbnailimage, A.linkactions, A.last_updated_date, A.last_updated_by, B.countryName " +
            "from ContentManage as A inner join Country as B on A.countryid=B.countryId")
    List<ContentManage> fetchDataInnerJoin();

服务等级：

public ContentManageListResponse queryAllActions() {
        List<ContentManage> contentManageList = contentManageRepository.fetchDataInnerJoin();
        List<ContentManageVO> contentManageVOList = new ArrayList<>();
        for (ContentManage contentManage : contentManageList) {
            ContentManageVO contentManageVO = new ContentManageVO();
            BeanUtils.copyProperties(contentManage,contentManageVO);
            contentManageVOList.add(contentManageVO);
        }
        return ContentManageListResponse.builder().contents(contentManageVOList).build();
    }

在我更改为如下之后，出现“ [Ljava.lang.Object;无法转换”异常：

服务等级

public ContentManageListResponse queryAllActions() {
        List<ContentManage> contentManageList = contentManageRepository.fetchDataInnerJoin();
        List<ContentManageVO> contentManageVOList = new ArrayList<>();
        for (Object contentManage : contentManageList) {
            ContentManageVO contentManageVO = new ContentManageVO();
            BeanUtils.copyProperties(contentManage,contentManageVO);
            contentManageVOList.add(contentManageVO);
        }
        return ContentManageListResponse.builder().contents(contentManageVOList).build();
    }

foreach 添加了对象，但对于上面的代码，我得到了空值 BeanUtils.copyProperties不管用

请任何人建议如何解决这个问题。

你的陈述

@Query("select A.id, A.position ,A.title,A.shortdescription,A.thumbnailimage, A.linkactions, A.last_updated_date, A.last_updated_by, B.countryName " +
            "from ContentManage as A inner join Country as B on A.countryid=B.countryId")

包含来自ContentManage and Country在选择. 但你的结果只是一个List<ContentManage>

为了解决这个问题，您可以创建一个新的 Dto 类，其中包含您需要的来自 A 和 B 的所有字段。此 Dto 类必须有一个全参数构造函数。然后代替

 "select A.id, A.position ,A.title,A.shortdescription,A.thumbnailimage, A.linkactions, A.last_updated_date, A.last_updated_by, B.countryName " +
            "from ContentManage as A inner join Country as B on A.countryid=B.countryId"

你可以写：

"select new com.you.package.YourDtoClass (A.id, A.position ,A.title,A.shortdescription,A.thumbnailimage, A.linkactions, A.last_updated_date, A.last_updated_by, B.countryName) " +
            "from ContentManage as A inner join Country as B on A.countryid=B.countryId"