我们希望在接口一上使用 DTO 投影,因此我们创建了以下 DTO 对象:
人员Dto
@Data
@Builder
@AllArgsConstructor
public class PersonDto {
private String name;
private String email;
private AddressDto address;
}
地址Dto
@Data
@Builder
@AllArgsConstructor
public class AddressDto {
private String address;
private String streetNumber;
}
一个存储库
@Repository
public interface PersonRepository extends JpaRepository<PersonEntity, Long> {
List<PersonDto> findAllDtoedBy();
}
然而,当调用时我们得到异常:
Caused by: org.hibernate.hql.internal.ast.QuerySyntaxException: Unable to locate appropriate constructor on class [com.example.projections.model.PersonDto]. Expected arguments are: java.lang.String, java.lang.String, com.example.projections.model.AddressEntity [select new com.example.projections.model.PersonDto(generatedAlias0.name, generatedAlias0.email, address) from com.example.projections.model.PersonEntity as generatedAlias0 left join generatedAlias0.address as address]
at org.hibernate.hql.internal.ast.QuerySyntaxException.convert(QuerySyntaxException.java:74) ~[hibernate-core-5.2.11.Final.jar:5.2.11.Final]
at org.hibernate.hql.internal.ast.ErrorCounter.throwQueryException(ErrorCounter.java:91) ~[hibernate-core-5.2.11.Final.jar:5.2.11.Final]
at org.hibernate.hql.internal.ast.QueryTranslatorImpl.analyze(QueryTranslatorImpl.java:272) ~[hibernate-core-5.2.11.Final.jar:5.2.11.Final]
at org.hibernate.hql.internal.ast.QueryTranslatorImpl.doCompile(QueryTranslatorImpl.java:189) ~[hibernate-core-5.2.11.Final.jar:5.2.11.Final]
请注意这一行:“...预期参数为:java.lang.String、java.lang.String、com.example.projections.model。地址实体...".
显然它需要模型对象地址实体,并且当 DTO 对象 (地址Dto) 被找到。
所以问题是,既然这适用于接口投影,我们是否期望 DTO 投影也支持它?
通过查看 GitHub 上的示例(https://github.com/spring-projects/spring-data-examples/blob/master/jpa/example/src/main/java/example/springdata/jpa/projections/CustomerRepository.java https://github.com/spring-projects/spring-data-examples/blob/master/jpa/example/src/main/java/example/springdata/jpa/projections/CustomerRepository.java)并且在 Spring Data JPA 文档中,我们没有看到这种情况的示例,但我们也没有看到明确的声明:isn't支持的