如何在Spring数据JPA中动态select列

Question

I have a typical Spring boot(2.7.6) application with apis' to fetch data in Kotlin .

Assume an entity called Employee

@Entity
data class Employee(
val id: Long,
val name: String,
val age: Int,
val interviewDate: LocalDate,
val joiningDate: LocalDate,
val resignationDate: LocalDate,
val lastWorkingDate: LocalDate
)

For brevity I have removed annotations like @Id etc from above entity class.

One of the APIs which vends out Employee data is such that, in request params I get something like dateType and it will have one of interviewDate/joiningDate/resignationDate/lastWorkingDate . And in request params dateFrom and dateTo , I get the date as an input like 2020-10-01 and 2022-12-30

For example, if api gets input like dateType=interviewDate&dateFrom=2020-10-01&dateTo=2022-12-30 then API has to return all the employee records whose interview_date column has values between 2020-10-01 and 2022-12-30

The example given above is just for ease of explaining. For real use-case have to fetch data from many tables and has many joins(inner/left/right).

Based on the input, what is the better way to select columns dynamically in repository method?

I tried Specification Criteria API , but it was a dead end because I cannot use joins as there is no mapping between Entities like @OneToMany etc.

I am trying with @Query to get data but have to duplicate lots of lines of sql for each condition. Example of one of the queries I have written in repository class is like below:

    @Query(
        """ 
select  
                t.a as A,
                t.b as B,
                tt.c as C,
                p.d as D,
                p.e as E
            from Employee p
                join Department t on p.some_id = t.id
                join PersonalData tt on tt.id = t.some_id
                left outer join SalaryInformation ps on p.id = ps.come_id
                left outer join ManagerInformation sbt on p.some_id = sbt.id
                . few more joins here
                .
                .
                            
            where p.id= :id and p.interviewDate>=:dateFrom and p.interviewDate<=:dateTo
""" ,
        nativeQuery = true
    )
    fun findByEmployeeIdForInterviewDate(employeeId: Long, dateFrom:String, dateTo: String, pageable: Pageable): Slice<EmployeeDetailsProjection>

With current approach, I have to repeat this query for remaining date columns which I dont want to as it looks ugly.

Any better suggestions will be really helpful:)

Answer 1

I tried Specification Criteria API, but it was a dead end because I cannot use joins as there is no mapping between Entities like @OneToMany etc.

Hibernate 6 introduces a JPA Criteria extension API which you can use to model joins to entities. To use Hibernate 6 you will have to update to Spring 3 though. For every JPA Criteria interface, Hibernate introduces a sub-interface prefixed with Jpa that contains the Hibernate JPA Criteria extensions. You could do eg

JpaEntityJoin<SalaryInformation> ps = ((JpaRoot<?>) root).join(SalaryInformation.class, SqmJoinType.LEFT);
ps.on(cb.equal(root.get("id"), ps.get("comeId")));