Analogue of @Formula annotation from JPA for Spring data neo4j?

Question

I'd like to calculate some properties of my domain objects at DB level using neo4j and return the read-only results. In JPA one can achieve this via @Formula annotation over field of domain object entity:

@Formula("(select avg(f.rating) from Feedback f where f.offer_id = offer_id)")
private Double rating;

What should one do to achieve the same behavior in Spring data neo4j? I wrote a Cypher query, but don't know where to use it.

Answer 1

A similar outcome can be achieved using @QueryResult

• Create a class with fields to hold return data.
• Annotate it with @QueryResult

Example: (in Kotlin, which is what I had on hand)

@QueryResult
open class Principal constructor(applicationToken: String,
                             profileId: String,
                             stageName: String,
                             showMeLaterDays: Float,
                             roles: Array<Role>)
{

    var applicationToken: String
    var profileId: String
    var stageName: String
    var showMeLaterDays: Float

    @Convert(RoleArrayAttributeConverter::class)
    var roles: Array<Role>



    init
    {
        this.applicationToken = applicationToken
        this.profileId = profileId
        this.stageName = stageName
        this.showMeLaterDays = showMeLaterDays
        this.roles = roles
    }

    //Provide a default constructor for OGM
    constructor() : this(applicationToken = "", profileId = "", stageName = "", showMeLaterDays = 0f,
        roles = emptyArray())
}

Then use it with a repository as follows:

@Query("MATCH (n:CandidateProfile {applicationToken: {0} }) 
    RETURN n.id as profileId, n.applicationToken as applicationToken, n.stageName as stageName, n.showMeLaterDays as showMeLaterDays, n.roles as roles;")
fun findByApplicationToken(token: String): Principal?

• Note the way that node properties are returned to correspond with the class field names.
• The same can be done with function results.