How to avoid unwanted queries hibernate query data when import data from entity to DTO - spring

Question

I have some entities below
#Entity
#Table("processitem")
public class Processitem {
...
#ManyToOne(fetch = FetchType.LAZY)
#JoinColumn(name="task")
public Task task;
#ManyToOne
#JoinColumn(name="user")
public User user;
//... and some more relationship to other
}
#Entity
#Table(name="task")
public class Task {
...
#OneToMany(mappedBy="task",cascade = CascadeType.ALL,orphanRemoval = true)
private Set<Processitem> processitem;
...
}
Now I import a List to List (I use a loop for to import data from entity to DTO), (around more 200 records) the hibernate execute a lots queries and performance is not good. Is there any solution to avoid that ? I tried using Entity Graph but it still doesn't improve (some time 2 queries is better 1 query with left join)

Answer 1

This is a perfect use case for Blaze-Persistence Entity Views.
I created the library to allow easy mapping between JPA models and custom interface or abstract class defined models, something like Spring Data Projections on steroids. The idea is that you define your target structure(domain model) the way you like and map attributes(getters) via JPQL expressions to the entity model.
A DTO model for your use case could look like the following with Blaze-Persistence Entity-Views:
#EntityView(Task.class)
interface TaskDto {
#IdMapping
Long getId();
String getName();
#Mapping(fetch = MULTISET)
Set<ProcessitemDto> getProcessitem();
}
#EntityView(Processitem.class)
public interface ProcessitemDto {
#IdMapping
Long getId();
#Mapping("user.name")
String getUserName();
}
Querying is a matter of applying the entity view to a query, the simplest being just a query by id.
TaskDto task = entityViewManager.find(entityManager, TaskDto.class, id);
The Spring Data integration allows you to use it almost like Spring Data Projections: https://persistence.blazebit.com/documentation/entity-view/manual/en_US/index.html#spring-data-features
You can make use of the various fetching strategies provided by Blaze-Persistence Entity-Views but the best one is usually the MULTISET fetch strategy. Here you can read more about it: https://persistence.blazebit.com/documentation/entity-view/manual/en_US/index.html#anchor-fetch-strategies