Closed Projection does not work with @EntityGraph [DATAJPA-1501]

[spring-projects-issues]

asfernandes opened DATAJPA-1501 and commented

I have entities that map others entities using @ManyToOne(fetch = FetchType.LAZY).

// Endereco.java

@Entity
@Table(name = "enderecos")
public class Endereco
{
	private Integer codigo;
	private Cidade cidade;

	@Id
	public Integer getCodigo()
	{
		return super.getCodigo();
	}

	public void setCodigo(Integer codigo)
	{
		this.codigo = codigo;
	}

	@ManyToOne(optional = false, fetch = FetchType.LAZY)
	@JoinColumn(name = "cid_codigo")
	public Cidade getCidade()
	{
		return cidade;
	}

	public void setCidade(Cidade cidade)
	{
		this.cidade = cidade;
	}
}

// Cidade.java

@Entity
@Table(name = "cidades")
public class Cidade
{
	private Integer codigo;
	private String nome;

	@Id
	public Integer getCodigo()
	{
		return super.getCodigo();
	}

	public void setCodigo(Integer codigo)
	{
		this.codigo = codigo;
	}

	public String getNome()
	{
		return nome;
	}

	public void setNome(String nome)
	{
		this.nome = nome;
	}
}

 

Then I have created a repository interface with a method using @EntityGraph:

@EntityGraph(type = EntityGraphType.FETCH,
	attributePaths = {
		"cidade"
	}
)
<T> List<T> findFetchCidade(Class<T> type);

 

And created projection interfaces:

public interface EnderecoProjection
{
	Integer getCodigo();
	CidadeProjection getCidade();

	/*
	@Value("#{target.codigo}")
	Integer getSomething();
	*/
}

public interface CidadeProjection
{
	Integer getCodigo();
	String getNome();
}

 

When I use findFetchCidade passing a EnderecoProjection, I have this error:

org.hibernate.QueryException: query specified join fetching, but the owner of the fetched association was not present in the select list

 

Note that if I uncomment the @Value annotation, the projection becomes opened and then no error happens

---

Affects: 2.1.4 (Lovelace SR4)

[spring-projects-issues]

Oliver Drotbohm commented

This looks like a wild mixture of entity graphs and projections, which we didn't quite anticipate before. What's the reason you need to mix those up? EnderecoProjection.getSomething() could just be a default method, couldn't it?

[spring-projects-issues]

asfernandes commented

If the projection is used directly (no generics) in findFetchCidade, the same thing happens

[spring-projects-issues]

asfernandes commented

Oliver Drotbohm I don't need the getSomething. It's used just to make the thing work. My real case is some nesting of projections (Endereco -> Cidade -> Estado -> Pais), that I need some fields of each, and I want to have LAZY in the entities

[spring-projects-issues]

asfernandes commented

Oliver Drotbohm you say the problem is the mixture of entity graphs and projections, but for me the problem seems to be about nested projections not creating a JPQL selecting the fetched entities. At least that seems to be what the error says.

It's weird because nested projections is documented as something supported

[SchlauFuchs]

Just found this after logging my issue (#2709)

[Eng-Fouad]

This repo demonstrates that entity graph is ignored in Spring-Data when it is used in combination with closed-projection:

https://github.com/Eng-Fouad/spring-closed-projection-entity-graph

[Eng-Fouad]

As a workaround:

@EntityGraph(value = "SomeEntityGraph")
EntityClass queryById(int id);

EntityClass entity = entityRepo.queryById(1);
EntityProjection entityProjection = new CollectionAwareProjectionFactory().createProjection(EntityProjection.class, entity);

However, the generated query will include all columns in SELECT clause, as the return type is EntityClass not EntityProjection.

[Eng-Fouad]

Any updates regarding this issue?
@odrotbohm @mp911de @schauder @gregturn @christophstrobl

[mp911de]

The actual question is: What should happen if a closed projection and an @EntityGraph are defined? Do we ignore the entity graph or do we ignore the reduction of columns as per the projection definition?