fix: @Query with projection and List<List> for Data JPA

[sdelamo]

This PR contains two failing tests annotated with @PendingFeature.

Given these Entities with a ManyToOne Relationship

package io.micronaut.data.hibernate.entities;

import io.micronaut.data.hibernate.querygroupby.TaskStatus;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.ManyToOne;
import java.time.LocalDate;
import java.util.Objects;
import java.util.UUID;

@Entity
public class MicronautTask {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    @Column(unique = true, nullable = false, updatable = false)
    private String uuid = UUID.randomUUID().toString();
    private String name;
    private String description;
    private LocalDate dueDate;

    private TaskStatus status;

    @ManyToOne(optional = false)
    private MicronautProject project;

...
}

and:

package io.micronaut.data.hibernate.entities;

import javax.persistence.CascadeType;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.OneToMany;
import java.util.HashSet;
import java.util.Objects;
import java.util.Set;

@Entity
public class MicronautProject {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    @Column(unique = true, nullable = false, updatable = false)
    private String code;
    private String name;
    private String description;
    @OneToMany(mappedBy = "project", orphanRemoval = true, fetch = FetchType.EAGER, cascade = CascadeType.ALL)
    private Set<MicronautTask> tasks = new HashSet<>();
   ....
}

Both methods in this repository fail:

package io.micronaut.data.hibernate.querygroupby;

import io.micronaut.data.annotation.Query;
import io.micronaut.data.annotation.Repository;
import io.micronaut.data.hibernate.entities.MicronautTask;
import io.micronaut.data.repository.CrudRepository;

import java.util.List;
@Repository
public interface MicronautTaskRepository extends CrudRepository<MicronautTask, Long> {
    @Query("select count(*), year(t.dueDate) from MicronautTask t group by year(t.dueDate)")
    Iterable<TasksPerYear> countByDueYear();

    @Query("select count(*), year(t.dueDate) from MicronautTask t group by year(t.dueDate)")
    List<List<Integer>> countByDueYearReturnList();
}

TasksPerYear is a POJO:

package io.micronaut.data.hibernate.querygroupby;

import io.micronaut.core.annotation.Introspected;

@Introspected
public class TasksPerYear {
    private final String number;
    private final String year;

    public TasksPerYear(String number, String year) {
        this.number = number;
        this.year = year;
    }

    public String getNumber() {
        return number;
    }

    public String getYear() {
        return year;
    }
}

I expected both to pass.

[dstepanov]

@radovanradic Can you please investigate the problem?

[radovanradic]

@radovanradic Can you please investigate the problem?

I will

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[radovanradic]

This works when written as

@Query("select count(*) as number, year(t.dueDate) as year from MicronautTask t group by year(t.dueDate)")

because of this line of our code in AbstractHibernateRepository

Set<String> properties = tuple.getElements().stream().map(TupleElement::getAlias).collect(Collectors.toCollection(() -> new TreeSet<>(String.CASE_INSENSITIVE_ORDER)));

expects that TupleElement::getAlias is not null and is one of properties Set which is number, year in our case. Then query can be executed.

[radovanradic]

And this fails with the error

Cannot create TypedQuery for query with more than one return using requested result type [java.util.List]

I tried to change it to List<Object[]> which I know Hibernate can return but does not work in our code and we probably can't support it now without some refactoring.