Ktor Client: Set up ktor client and get data from typicode

Ktor Client: Set Up Ktor Client and Get Data from Typicode

In this tutorial, you'll learn how to set up a Ktor HTTP client in Kotlin and fetch JSON data from the Typicode API, a popular free REST API for testing. This example demonstrates making a GET request and parsing the response to work with remote data efficiently.

Code

import io.ktor.client.*
import io.ktor.client.engine.cio.*
import io.ktor.client.request.*
import io.ktor.client.statement.*
import io.ktor.client.call.*
import io.ktor.client.plugins.contentnegotiation.*
import io.ktor.serialization.kotlinx.json.*
import kotlinx.coroutines.runBlocking
import kotlinx.serialization.Serializable
import kotlinx.serialization.json.Json

// Define a data class matching the JSON structure from Typicode
@Serializable
data class Post(
  val userId: Int,
  val id: Int,
  val title: String,
  val body: String
)

fun main() = runBlocking {
  // Create Ktor client with CIO engine and JSON serialization support
  val client = HttpClient(CIO) {
    install(ContentNegotiation) {
      json(Json {
        ignoreUnknownKeys = true // Ignore extra fields in JSON
      })
    }
  }

  try {
    // Make a GET request to fetch a post from Typicode API
    val post: Post = client.get("https://jsonplaceholder.typicode.com/posts/1").body()
    println("Post title: ${post.title}")
    println("Post body: ${post.body}")
  } catch (e: Exception) {
    println("Error fetching data: ${e.message}")
  } finally {
    client.close()
  }
}

Key Points

• Ktor Client can be configured with different engines; CIO is a lightweight asynchronous engine.
• ContentNegotiation plugin with Kotlinx Serialization enables automatic JSON parsing into Kotlin data classes.
• Use suspend functions and runBlocking to perform asynchronous network calls in a simple main function.
• Always close the client after use to free resources and avoid leaks.
• Typicode provides a simple REST API ideal for testing HTTP clients and JSON parsing.