[Kotlin Spring boot] A simple demo app

Structure:

tempalates/seatBooking.html:

<!DOCTYPE html>
<html lang="en" xmlns:th="http://www.thymeleaf.org">
<head>
    <meta charset="UTF-8">
    <title>com.virtualpairprogrammers.theater.services.TheaterService Booking</title>
</head>
<body>
    <h1>com.virtualpairprogrammers.theater.services.TheaterService Booking</h1>
<h2>Seat availability</h2>

    <form action="/checkAvailability" th:object="${bean}" method="POST">
    <p>Check if seat number
        <select th:field="*{selectedSeatNum}">
            <option th:each="n : ${bean.seatNums}" th:value="${n}" th:text="${n}" />
        </select>
         in row
        <select th:field="*{selectedSeatRow}">
            <option th:each="r : ${bean.seatRows}" th:value="${r}" th:text="${r}" />
        </select>
        is available <input type="submit"/></p>

    </form>

    <p th:text="${bean.result}"></p>
</body>
</html>

Control/MainController:

package com.virtualpairprogrammers.theater.control

import com.virtualpairprogrammers.theater.services.BookingService
import com.virtualpairprogrammers.theater.services.TheaterService
import org.springframework.beans.factory.annotation.Autowired
import org.springframework.stereotype.Controller
import org.springframework.web.bind.annotation.RequestMapping
import org.springframework.web.bind.annotation.RequestMethod
import org.springframework.web.servlet.ModelAndView

@Controller
class MainController {

    @Autowired
    lateinit var theaterService: TheaterService

    @Autowired
    lateinit var bookingService: BookingService

    @RequestMapping("")
    fun homePage() : ModelAndView {
        return ModelAndView("seatBooking", "bean", CheckAvailabilityBackingBean())
    }

    @RequestMapping("checkAvailability", method= arrayOf(RequestMethod.POST))
    fun checkAvailability(bean: CheckAvailabilityBackingBean): ModelAndView {
        val selectedSeat = theaterService.find(bean.selectedSeatNum, bean.selectedSeatRow)
        val result =  bookingService.isSeatFree(selectedSeat)
        bean.result = "Seat $selectedSeat is " + if (result) "available" else "booked"
        return ModelAndView("seatBooking", "bean", bean)
    }
}

/*
* A typical JavaServer Faces application includes one or more backing beans,
* each of which is a type of JavaServer Faces managed bean that can be associated with
* the components used in a particular page.
* This section introduces the basic concepts of creating, configuring,
* and using backing beans in an application.
* */
class CheckAvailabilityBackingBean() {
    val seatNums = 1..36
    val seatRows = 'A'..'O'
    // below must be var because those data are sent back and forward between
    // server and template
    var selectedSeatNum: Int = 1
    var selectedSeatRow: Char = 'A'
    var result: String = ""
}

domain/Seat:

package com.virtualpairprogrammers.theater.domain

import java.math.BigDecimal

data class Seat(val row: Char, val num: Int, val price: BigDecimal, val description: String) {
    override fun toString(): String = "Seat $row-$num $$price ($description)"
}

services/TheaterService:

package com.virtualpairprogrammers.theater.services

import com.virtualpairprogrammers.theater.domain.Seat
import org.springframework.stereotype.Service
import java.math.BigDecimal


@Service
class TheaterService {

    private val hiddenSeats = mutableListOf<Seat>()

    constructor() {

        fun getPrice(row: Int, num: Int) : BigDecimal {
            return when {
                row >=14 -> BigDecimal(14.50)
                num <=3 || num >= 34 -> BigDecimal(16.50)
                row == 1 -> BigDecimal(21)
                else -> BigDecimal(18)
            }

        }

        fun getDescription(row: Int, num: Int) : String {
            return when {
                row == 15 -> "Back Row"
                row == 14 -> "Cheaper Seat"
                num <=3 || num >= 34 -> "Restricted View"
                row <=2 -> "Best View"
                else -> "Standard Seat"
            }
        }

        for (row in 1..15) {
            for (num in 1..36) {
                hiddenSeats.add(Seat((row+64).toChar(), num, getPrice(row,num), getDescription(row,num) ))
            }
        }
    }

    val seats
    get() = hiddenSeats.toList()


    fun find(num: Int, row: Char): Seat {
        return seats.filter {it.row === row && it.num === num }.first()
    }
}

services/BookingService:

package com.virtualpairprogrammers.theater.services

import com.virtualpairprogrammers.theater.domain.Seat
import org.springframework.stereotype.Service

@Service
class BookingService() {

    fun isSeatFree(seat: Seat): Boolean {
        return true
    }
}