Appendix: Code Snippets

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SpringContext

Double.round(decimals: Int): Double

A Spring component that allows non-components to load beans; SpringContext implements ApplicaitonContextAware to get the context, then implements a method in its companion object to allow loading a bean. Based on a Java component of the same name byJay Ta'ala: https://me.jaytaala.com/super-simple-approach-to-accessing-spring-beans-from-non-spring-managed-classes-and-pojos but re-written and simplified for Kotlin.

/*
* Copyright © 2025 Jim Hamilton.
* All rights reserved.
*/

import org.springframework.beans.factory.getBean

import org.springframework.context.ApplicationContext

import org.springframework.stereotype.Component

@Component

class SpringContext(val context: ApplicationContext) {

    init {

        instance = this

    }

    companion object {

        lateinit var instance: SpringContext

        inline fun <reified T : Any> getBean(): T = instance.context.getBean()

    }

}

Usage: 

    val mapper = SpringContext.getBean<ObjectMapper>()

or

    val mapper: ObjectMapper = SpringContext.getBean()

An extension method to round a double to any desired number of decimal places–including a negative number.  Rounding to 2 places will round to the nearest hundredth; rounding to -2 places will round to the nearest hundred.

// Copyright ©2025 Jim Hamilton. All rights reserved.

import kotlin.math.pow
import kotlin.math.round

fun Double.round(decimals: Int): Double {
   val multiplier = 10.0.pow(decimals)
   return round(this * multiplier) / multiplier
}

Usage:

import kotlin.math.PI

    val pi = PI.round(4)     // 3.1416

    val thousandPi = (1000.0*PI).round(-1)     // 3140