java - createNativeQuery 映射到 POJO(非实体)

Question

乍一看我有一个简单的问题:

entityManager()
.createNativeQuery("select count(*) as total, select sum(field) as total_sum ... blabla") 

我想将选择结果写入 POJO，如下所示:

public class AggregateStatsDto {

    private int total;

    private long totalSum;

    // getters, setters, cosntructors
}

实现此目标的最佳方法是什么？

我可以使用 JPA 2.1 并尝试将 @SqlResultSetMapping 与 @ConstructorResult 结合使用:

@SqlResultSetMapping(name = "AggregateStatsResult", classes = {
        @ConstructorResult(targetClass = AggregateStatsDto.class,
                columns = {
                        @ColumnResult(name = "total"),
                        @ColumnResult(name = "totalSum")
                })
})
public class AggregateStatsDto {

        private long total;

        private int totalSum;

        // getters, setters, cosntructors
    }

查询:

AggregateStatsDto result = (AggregateStatsDto) entityManager()
    .createNativeQuery("select count(*) as total, select sum(field) as total_sum ... blabla", "AggregateStatsResult")
    .getSingleResult();

但运气不好。它似乎无论如何都想要@Entity。但我只想要一个 POJO。

org.hibernate.MappingException: Unknown SqlResultSetMapping [AggregateStatsResult]"

提前致谢!

Answer 1

将您的 @SqlResultSetMapping 注释放在一个实际实体的类中，而不是 DTO 类中。当您在非实体中注释 SqlResultSetMapping 时，您的实体管理器无法发现您的映射。

@SqlResultSetMapping(name = "AggregateStatsResult", classes = {
    @ConstructorResult(targetClass = AggregateStatsDto.class,
            columns = {
                    @ColumnResult(name = "total"),
                    @ColumnResult(name = "totalSum")
            })
})
@Entity
public class SomeOtherClassWhichIsAnEntity {