Simple Controller without dynamic routing

SimpleController.kt

package com.myblockbuster.core.controllers

import com.fasterxml.jackson.databind.ObjectMapper
import com.myblockbuster.core.InvalidArguments
import com.myblockbuster.core.Model
import com.myblockbuster.core.Request

/**
 * Controller that receives a request and reply with a message of type {@link M}
 * @param M Model type
 */
interface Controller<M> {

    fun anyToInt(value: Any, valueType: String = "page"): Int {
        return when (value) {
            is String -> value.toIntOrNull() ?: throw Exception("$valueType must be a number")
            is Int -> value
            else -> throw Exception("$valueType must be a number")
        }
    }

    fun getStringAnyMap(request: Request, key: String): Map<String, Any> {
        return if (request.input.containsKey(key) && request.input[key] != null)
            request.input[key] as Map<String, Any>
        else
            emptyMap()
    }

    fun getResource(request: Request): String {
        return request.input["resource"] as String
    }

    fun getHeaders(request: Request) : Map<String, Any> {
        return getStringAnyMap(request, "headers")
    }

    fun getPathParameters(request: Request) : Map<String, Any> {
        return getStringAnyMap(request, "pathParameters")
    }

    fun getQueryStringParameters(request: Request) : Map<String, Any> {
        return getStringAnyMap(request, "queryStringParameters")
    }

    fun getRawBody(request: Request) : Any {
        if (request.input["body"] != null)
            return if (request.input["body"] is String) request.input["body"] as String else request.input["body"] as Map<String, Any>
        else
            throw InvalidArguments("body")
    }

    fun <T : Model> getEntity(rawBody: Any, cls: Class<T>): T {
        val objectMapper = ObjectMapper()

        return if (rawBody is String) objectMapper.readValue(rawBody, cls) else objectMapper.convertValue(rawBody, cls)
    }
}