A Kotlin wrapper for Typesafe Config

Config4k

Config for Kotlin.

Config4k is a lightweight Typesafe Config wrapper for Kotlin and inspired by ficus, providing simple extension functions Config.extract<T> and Any.toConfig to convert between Config and Kotlin Objects.

Table of Contents

• Installation
• Usage
  • Delegated Properties
  • Deserialization
  • Data Classes
  • Nullable
  • Enum
  • Serialization
  • String
  • ConfigRenderOptions
• Supported types
• Contribute ## Installation

Gradle:

repositories {
    mavenCentral()
}


dependencies {
    compile 'io.github.config4k:config4k:xxx' // See the `Download` badge
}

Usage

Delegated Properties

By far the simplest way to use config4k is via Kotlin Delegated Properties:

val config = ConfigFactory.parseString("""
                                          |stringValue = hello
                                          |booleanValue = true
                                          |""".trimMargin())

val stringValue: String by config
println(stringValue) // hello

val nullableStringValue: String? by config
println(nullableStringValue) // null

val booleanValue: Boolean by config
println(booleanValue) // true

Deserialization

Config.extract<T> converts Config to T.

Map

Maps can be serialized with String keys

val config = ConfigFactory.parseString("""
                                          |map {  
                                          |  foo = 5
                                          |  bar = 6
                                          |}""".trimMargin())
val map: Map<String, Int> = config.extract<Map<String, Int>>("map")
println(map["foo"] == 5) // true
println(map["bar"] == 6) // true

or with arbitrary keys

val config = ConfigFactory.parseString("""
                                          |map = [{  
                                          |  key = 5
                                          |  value = "foo"
                                          |}
                                          |{
                                          |  key = 6
                                          |  value = "bar"
                                          |}]""".trimMargin())
val map: Map<Int, String> = config.extract<Map<Int, String>>("map")
println(map[5] == "foo") // true
println(map[6] == "bar") // true

Test Class: TestMap.kt

Data Classes

Config4k has no option to use different names between code and config file.

data class Person(val name: String, val age: Int)

val config = ConfigFactory.parseString("""
                                          |key {  
                                          |  name = "foo"
                                          |  age = 20
                                          |}""".trimMargin())
val person: Person = config.extract<Person>("key")
println(person.name == "foo") // true
println(person.age == 20) // true

For more details, please see TestArbitraryType.kt

Nullable

Using extract<T?> is the better way than Config.hasPath(). extract<T?> returns T when the path exists and null when it does not exist.

val config = ConfigFactory.parseString("""key = 10""")
val key = config.extract<Int?>("key")
val foo = config.extract<Int?>("foo")
println(key == 10) // true
println(foo == null) // true

Test Class: TestNullable.kt

Enum

Config4k also supports Enum. Enum is converted to String of its name in the config file.

enum class Size {
    SMALL,
    MEDIUM,
    LARGE
}

val config = ConfigFactory.parseString("""key = SMALL""")
val small = config.extract<Size>("key")
println(small == Size.SMALL) // true

Test Class: TestEnum.kt

Serialization

Any.toConfig converts the receiver object to Config.

String

You can use ConfigValue.render() to serialize Config. Config4k helps getting Config of the class you want to serialize.

data class Person(val name: String, val age: Int)
val person = Person("foo", 20).toConfig("person")
println(person.root().render())

Output:

{
    # hardcoded value
    "person" : {
        # hardcoded value
        "age" : 20,
        # hardcoded value
        "name" : "foo"
    }
}

Test Class: TestToConfigForArbitraryType.kt

ConfigRenderOptions

Typesafe Config's class ConfigRenderOptions is the argument of ConfigValue.render.

// If setJson(false) is called, ConfigValue.render returns HOCON
data class Person(val name: String, val age: Int)
val person = Person("foo", 20).toConfig("person")
val options = ConfigRenderOptions.defaults().setJson(false)
println(person.root().render(options))

Output:

    # hardcoded value
person {
    # hardcoded value
    age=20
    # hardcoded value
    name=foo
}

// setOriginComments(false) removes comments
data class Person(val name: String, val age: Int)
val person = Person("foo", 20).toConfig("person")
val options = ConfigRenderOptions.defaults()
                        .setJson(false)
                        .setOriginComments(false)
println(person.root().render(options))

Output:

person {
    age=20
    name=foo
}

Supported types

Property delegation, extract and toConfig support these types:

• Primitive types
  • Boolean
  • Byte
  • Int
  • Long
  • Float
  • Double
• String
• import java.io.File
• import java.nio.file.Path
• java.time.Duration
• java.time.Period
• java.time.temporal.TemporalAmount
• kotlin.text.Regex
• Collections
  • List
  • Set
  • Map<K, V>
  • Array<T> (You can use Array<Int>, but can't use Array<Array<Int>>)
• Nullable T?
• Typesafe Config classes(Calling toConfig is meaningless)
  • com.typesafe.config.Config
  • com.typesafe.config.ConfigValue
  • com.typesafe.config.ConfigMemorySize
• Enum
• Data classes

See [SelectReader.kt](src/main/io.github.config4k/readers/SelectReader.kt) for the exhaustive list.

Snapshots

All snapshot artifacts are available in the Sonatype snapshots repository.

Contribute

Would you like to contribute to Config4k?
Take a look at CONTRIBUTING.md