Value Providers

The ValueProvider interface is a generic abstraction used across Kore and the DavilsX ecosystem for retrieving values by key. It provides a consistent way to access configuration values, environment variables, or any other key-value based data.

The ValueProvider Interface

The interface com.davils.kore.ValueProvider<T> defines several methods for safe and convenient value retrieval.

Basic Retrieval

getValueOrNull(key): Returns the value or null if not found.
getValueOrThrow(key): Returns the value or throws a NoSuchElementException.
getValueOrDefault(key, default): Returns the value or a provided default.

Functional API

Value providers support functional patterns for working with values:

getValueResult(key): Returns the value wrapped in a Result.
useValue(key) { value -> ... }: Executes a block with the retrieved value.
mapValue(key) { value -> ... }: Transforms the retrieved value.

Operators

You can use the index operator and the in operator with value providers:

val provider: ValueProvider<String> = // ...
val value = provider["my.key"]
if ("my.key" in provider) {
    // ...
}

Implementations in Kore

Kore provides several implementations of ValueProvider:

Environment

The Environment object implements ValueProvider<String>, providing access to system environment variables across platforms.

import com.davils.kore.system.Environment

val path = Environment["PATH"]

PropertiesScope (JVM)

The PropertiesScope used in the properties { } DSL also implements ValueProvider<String> for JVM system properties.

import com.davils.kore.system.properties

properties {
    val version = getValueOrDefault("java.version", "unknown")
}

Creating Custom Providers

You can easily create your own value providers by implementing the ValueProvider interface. You only need to implement getValueOrNull(key).

class MyConfigProvider(private val config: Map<String, String>) : ValueProvider<String> {
    override fun getValueOrNull(key: String): String? = config[key]
}

07 May 2026