Type mismatch: inferred type is () -> JoinColumn but JoinColumn was expected

We are using Corda 4, Springboot web server and Postgresql 11.

Following are the versions of Corda platform, Springboot server, and other essential dependencies used-

cordaReleaseGroup=net.corda
cordaVersion=4.0
gradlePluginsVersion=4.0.45
kotlinVersion=1.2.71
junitVersion=4.12
quasarVersion=0.7.10
spring_version = '4.3.11.RELEASE'
spring_boot_version = '2.0.2.RELEASE'
spring_boot_gradle_plugin_version = '2.1.1.RELEASE'
jvmTarget = "1.8"
log4jVersion =2.11.2
platformVersion=4
slf4jVersion=1.7.25
nettyVersion=4.1.22.Final

We were able to achieve the sending of single transaction record to a target vault table, from a node to another.

We have come across a requirement in which the transaction is of One-to-many type, for which parent-child tables need to be created in the vault.

Following is the code to create the schema for the parent-child tables but it throws error on compilation -
"Type mismatch: inferred type is () -> JoinColumn but JoinColumn was expected".

import net.corda.core.schemas.MappedSchema
import net.corda.core.schemas.PersistentState
import javax.persistence.*;
import java.io.Serializable;
import java.util.List;
import java.util.UUID

object Schema1

object SchemaV1 : MappedSchema(
    schemaFamily = Schema1.javaClass,
    version = 1,
    mappedTypes = listOf(PersistentEmployees::class.java,PersistentEmployeeVehicles::class.java)) 
{
@Entity
@Table(name = "TBL_EMPLOYEES")
class PersistentEmployees(
    @Column(name = "EmployeeId")
    var Pid: Long,

    @Column(name = "EmployeeName")
    var EmployeeName: String,

    @Column(name = "EmployeeAddress") 
    var EmployeeAddress: String,

    @OneToMany(cascade = [(CascadeType.PERSIST)])
    @JoinColumns({
        JoinColumn(name = "output_index", referencedColumnName = "output_index");
        JoinColumn(name = "transaction_id", referencedColumnName = "transaction_id") })        
    private val EmpVehicles:List<PersistentEmployeeVehicles>
    
) : PersistentState(), Serializable

@Entity
@Table(name = "TBL_EMPLOYEE_VEHICLES")
class PersistentEmployeeVehicles(
    @Column(name = "ID")
    var ID: UUID,

    @Column(name = "VEHICLETYPE") 
    var VEHICLETYPE: String,
    
    @Column(name = "VEHICLEMODEL") 
    var VEHICLEMODEL: String,
    
    @Column(name = "VEHICLENUMBER") 
    var VEHICLENUMBER: String
)
}

Question 1: What would be the cause of the error and also the solution (if possible)?

We used "Car insurance" "One-to-many" mapping sample from Corda Git Hub. Following are the links-

"https://github.com/corda/samples/blob/release-V4/carinsurance-QueryableState/contracts/src/main/java/net/corda/examples/carinsurance/schema/PersistentInsurance.java"

"https://github.com/corda/samples/blob/release-V4/carinsurance-QueryableState/contracts/src/main/java/net/corda/examples/carinsurance/schema/PersistentClaim.java"

The syntax for declaring arrays within annotations is different between Java and Kotlin, for Kotlin, you should use [] like the following:

@JoinColumns(value = [
    JoinColumn(name = "output_index", referencedColumnName = "output_index"),
    JoinColumn(name = "transaction_id", referencedColumnName = "transaction_id") ])      
private val EmpVehicles:List<PersistentEmployeeVehicles>