pkl-config-kotlin Library
The pkl-config-kotlin library extends pkl-config-java with Kotlin specific extension methods and object converters. We recommend that Kotlin projects depend on this library instead of pkl-config-java.
Installation
The pkl-config-kotlin library is available from Maven Central. It requires Java 11 or higher and Kotlin 1.5 or higher.
Gradle
To use the library in a Gradle project, declare the following dependency:
-
Kotlin
-
Groovy
dependencies {
implementation("org.pkl-lang:pkl-config-kotlin:0.25.3")
}
repositories {
mavenCentral()
}dependencies {
implementation "org.pkl-lang:pkl-config-kotlin:0.25.3"
}
repositories {
mavenCentral()
}Maven
To use the library in a Maven project, declare the following dependency:
<project>
<dependency>
<groupId>org.pkl-lang</groupId>
<artifactId>pkl-config-kotlin</artifactId>
<version>0.25.3</version>
</dependency>
</project>Usage
Below is the Kotlin version of the Java ConfigEvaluator example. Differences to the Java version are called out.
val evaluator = ConfigEvaluator.preconfigured().forKotlin() (1)
val config = evaluator.use { (2)
it.evaluateText("""pigeon { age = 5; diet = "Seeds" }""")
}
val pigeon = config["pigeon"] (3)
val age = pigeon["age"].to<Int>() (4)
val hobbies = pigeon["diet"].to<List<String>>() (5)| 1 | Use the forKotlin() method to preconfigure the builder with Kotlin specific conversions.
In particular, forKotlin() eliminates the need to annotate constructor parameters of Kotlin classes and Kotlin data classes with @Named. |
| 2 | The evaluator should be closed once it is no longer needed.
Here this is done with a Kotlin use {} expression.
Any data returned by the evaluator before calling close() remains valid. |
| 3 | Navigate to the "pigeon" child.
The subscript notation is shorthand for config.get("pigeon"). |
| 4 | Convert "age" to Int with the Config.to() extension method.
The target type is provided as a type argument.
Always use Config.to() instead of Config.as() in Kotlin. |
| 5 | Config.to() makes conversions to parameterized types straightforward:
to<List<String>>() instead of as(JavaType.listOf(String::class.java)). |
For properties that are allowed to be null, convert to a nullable type:
val evaluator = ConfigEvaluator.preconfigured().forKotlin()
val config = evaluator.use {
it.evaluateText("name = null") (1)
}
val name = config["name"].to<String?>() (2)| 1 | To indicate that null is an allowed value, convert to the nullable type String?.
Converting to String would result in a ConversionException. |
For a ready-to-go example with full source code, see config-kotlin in the pkl/pkl-examples repository.