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

Question

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"

Answer 1

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>