Spring Data JPA projection to records using native queries does not work

[pashazadeh]

I have used Interface based projection using native queries for long time, but now according to Spring Data JPA reference documentstions record-based projections must work too, but it seems it does not support custom native queries.

As proxied interfaces are not so friendly during debugging, using records would be great, but it seems the conversion does not work with records.

Can this issue be solved?

By the way I am using Spring Data 3.2.3 (latest release till now)

[mp911de]

but it seems it does not support custom native queries.

Care to elaborate?
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[pashazadeh]

Well I like to contribute, but not sure how to implement it.

I am thinking of a ConverterFactory<Tuple, Record>, but not sure how to implement it of the Record type has complex components (such as nested Records, nested interfaces, or objects).

For simple cases which Record just contains, primitives, wrappers, and simple types such as String, Date, java.time classes (anything Spring ConversionService can convert), it can be done.

[pashazadeh]

I digged more in Spring Data JPA sources in class org.springframework.data.jpa.repository.query.NamedQuery, method Class<?> getTypeToRead(ReturnedType returnedType) just returns tuple when ReturnType is an interface, and not a record, so now Hibernate returns an Object[] which is not suitable for extracting results columns by name.

Well I am using named queries, as in our project using queries in annotations is prohibited (as queries are usually so long).

[pashazadeh]

A mismatch between using native-named-queries and native-queries within annotation, when I put the query text in annotation, the return type is now a jakarta.persistence.Tuple (it occurs for annotation parameter nativeQuery = true).

But my named query was also native (and I have @Query annotation with nativeQuery=true), but in this case the expecting type from Hibernate is not a jakarta.persistence.Tuple, as
em.createNamedQuery(queryName)
is called instead of
em.createNamedQuery(queryName, typeToRead)

[pashazadeh]

In Hibernate you can unwrap a jakarta.persistence.Query to org.hibernate.Query and then call setTupleTransformer(NativeQueryConstructorTransformer), it converts query result to an object using constructor arguments (which is suitable for Records). But as I have no experience with EclipseLink, don't know how to do that there.

By the way Hibernate's NativeQueryConstructorTransformer does not support proper conversion, a specific implementation of TupleTransformer which uses Spring ConversionService would be much nicer.

[ah1508]

Answers to this "problem" from Spring team here: #2757

[mp911de]

This is pretty much a duplicate of #2757. We will fix the issue within the scope of the linked ticket.