HQL查询到复杂的DTO

Question

I have an issue with mapping HQL query to complex DTO. By complex DTO I mean DTO that composites another DTOs / collection DTOs. I tried to find solution but didn't find anything that can suit my requirements. For instance there is a DTO (I omit properties for simplicity):

public class Consignment {

  private List<OrderData> orderData;
  private List<AttributesData> attributesData;
  private CostData costData;

  public Consignment(List<OrderData> orderData, List<AttributesData> attributesData, CostData costData) {
    //setting fields
  }

}

The HQL lets to create DTO object through constructor by passing columns from result set as parameters. Is it possible to create subqueries or smth. Else to fetch data in collection and then pass it as arguments in main DTO? It looks that it is impossible but maybe I missed something.

Otherwise there is only the way to do that is to fetch data in separate HQL queries and then create main DTO as plain Java object. If anyone has alternative ideas how to do that - please share your ideas.

Answer 1

您可以像这样在同一查询中获取其他数据：

FROM Consignment cons JOIN FETCH cons.orderData ord

Answer 2

I created Blaze-Persistence Entity Views for exactly that use case. You essentially define DTOs for JPA entities as interfaces and apply them on a query. It supports mapping nested DTOs, collection etc., essentially everything you'd expect and on top of that, it will improve your query performance as it will generate queries fetching just the data that you actually require for the DTOs.

The entity views for you example could look like this

@EntityView(ConsignmentEntity.class)
interface Consignment {
  List<OrderData> getOrderData();
  List<AttributesData> getAttributesData();
  CostData getCostData();
}

@EntityView(OrderDataEntity.class)
interface OrderData {
  // attributes of OrderDataEntity that you need
}
@EntityView(AttributesDataEntity.class)
interface AttributesData {
  // attributes of AttributesDataEntity that you need
}
@EntityView(CostDataEntity.class)
interface CostData {
  // attributes of CostDataEntity that you need
}

Querying could look like this

List<Consignment> dtos = entityViewManager.applySetting(
  EntityViewSetting.create(Consignment.class),
  criteriaBuilderFactory.create(em, ConsignmentEntity.class)
).getResultList();