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How to read and write YAML files in Kotlin

How to read and write YAML files in Kotlin.

Here's a step-by-step tutorial on how to read and write YAML files in Kotlin:

Prerequisites​

Before we begin, make sure you have the following in place:

  • Kotlin installed on your machine
  • A text editor or an Integrated Development Environment (IDE) of your choice

Step 1: Add YAML dependency​

To work with YAML files in Kotlin, we need to include a YAML library. In this tutorial, we'll use the snakeyaml library. Open your build.gradle.kts file and add the following dependency:

dependencies {
    implementation("org.yaml:snakeyaml:1.28")
}

If you're using Maven, you can add the dependency to your pom.xml file.

Step 2: Read a YAML file​

To read a YAML file, follow these steps:

  1. Import the necessary classes:
import org.yaml.snakeyaml.Yaml
import java.io.File
  1. Create an instance of the Yaml class:
val yaml = Yaml()
  1. Read the YAML file and parse it into a Map:
val file = File("path/to/your/file.yaml")
val data = yaml.load<Map<String, Any>>(file.inputStream())
  1. Access the data from the Map:
val name = data["name"] as String
val age = data["age"] as Int

Here's an example of reading a YAML file named example.yaml:

name: John
age: 25
val file = File("example.yaml")
val data = yaml.load<Map<String, Any>>(file.inputStream())
val name = data["name"] as String
val age = data["age"] as Int

println("Name: $name")
println("Age: $age")

Step 3: Write a YAML file​

To write data to a YAML file, follow these steps:

  1. Import the necessary classes:
import org.yaml.snakeyaml.DumperOptions
import org.yaml.snakeyaml.Yaml
import java.io.File
  1. Create an instance of the Yaml class:
val yaml = Yaml()
  1. Create a Map object with the data you want to write:
val data = mapOf(
    "name" to "John",
    "age" to 25
)
  1. Set up the options for the YAML output:
val options = DumperOptions()
options.defaultFlowStyle = DumperOptions.FlowStyle.BLOCK
  1. Write the data to a YAML file:
val file = File("path/to/your/file.yaml")
yaml.dump(data, file.writer(), options)

Here's an example of writing data to a YAML file:

val data = mapOf(
    "name" to "John",
    "age" to 25
)

val options = DumperOptions()
options.defaultFlowStyle = DumperOptions.FlowStyle.BLOCK

val file = File("example.yaml")
yaml.dump(data, file.writer(), options)

Step 4: Verify the output​

After running the code to read or write a YAML file, you can verify the output by checking the contents of the file. For example, if you read a YAML file, you can print the values to the console. If you write a YAML file, you can open the file and check its contents.

That's it! You now know how to read and write YAML files in Kotlin using the snakeyaml library. Feel free to explore more advanced features of the library to suit your specific needs.