JPA Join Query(native query) custom dto

Question

Hi I am trying to join 3 table and fetch the collective result i.e dto using following query

SELECT f.id, u.email,
count(distinct l.id) as likes_count,
count(dis         


        

Answer 1

You cannot use constructor expression (NEW operator) with Native Queries.

You could use JPA constructor result. This looks like:

Query q = em.createNativeQuery(
    "SELECT c.id, c.name, COUNT(o) as orderCount, AVG(o.price) AS avgOrder " +
    "FROM Customer c " +
    "JOIN Orders o ON o.cid = c.id " +
    "GROUP BY c.id, c.name",
    "CustomerDetailsResult");

@SqlResultSetMapping(name="CustomerDetailsResult",
    classes={
        @ConstructorResult(targetClass=com.acme.CustomerDetails.class,
            columns={
                @ColumnResult(name="id"),
                @ColumnResult(name="name"),
                @ColumnResult(name="orderCount"),
                @ColumnResult(name="avgOrder", type=Double.class)})
    })

Or you could convert FeedDetails to an interface and try Spring Data JPA Interface projection: https://docs.spring.io/spring-data/jpa/docs/current/reference/html/#projections

Or if you don't like these option there is a little library called QLRM: https://github.com/simasch/qlrm/blob/master/ConstructorResult.md