GroceryItem.kt

package za.co.dubedivine.groceryapp.model

import javax.persistence.Entity
import javax.persistence.GeneratedValue
import javax.persistence.GenerationType
import javax.persistence.Id

@Entity
data class GroceryItem(var name: String, var isAvailable: Boolean) {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    var id: Long = 0L

    constructor(): this ("", false)
}

oneliner-GroceryItem.kt

package za.co.dubedivine.groceryapp.model

import javax.persistence.Entity
import javax.persistence.GeneratedValue
import javax.persistence.GenerationType
import javax.persistence.Id

@Entity
data class GroceryItem(var name: String = "",
                      var isAvailable: Boolean = false,
                      @Id
                      @GeneratedValue(strategy = GenerationType.AUTO)
                      var id: Long = 0)