Kotlin Ktor

🚀 What is Ktor?

Ktor is a modern, asynchronous web framework for Kotlin that makes building web applications and APIs simple and fun. Create powerful server-side applications with minimal boilerplate code.


// Simple Ktor server
fun main() {
    embeddedServer(Netty, port = 8080) {
        routing {
            get("/") {
                call.respondText("Hello, Ktor!")
            }
        }
    }.start(wait = true)
}

Ktor Features

🌐

HTTP Server

Create REST APIs and web servers

get("/api/users") {
    call.respond(users)
}

📱

HTTP Client

Make HTTP requests easily

val client = HttpClient()
val response = client.get("https://api.example.com")

🔌

Plugins

Extend functionality with plugins

install(ContentNegotiation) {
    json()
}

⚡

Coroutines

Asynchronous programming support

suspend fun fetchData() {
    delay(1000)
    return "Data"
}

🔹 Basic Ktor Server

Create a simple web server with routing:

import io.ktor.server.application.*
import io.ktor.server.engine.*
import io.ktor.server.netty.*
import io.ktor.server.response.*
import io.ktor.server.routing.*

fun main() {
    embeddedServer(Netty, port = 8080) {
        routing {
            get("/") {
                call.respondText("Welcome to Ktor!")
            }
            get("/hello/{name}") {
                val name = call.parameters["name"]
                call.respondText("Hello, $name!")
            }
        }
    }.start(wait = true)
}

Server Response:

GET / → "Welcome to Ktor!"

GET /hello/John → "Hello, John!"

🔹 JSON API Example

Build a REST API that handles JSON:

import io.ktor.serialization.kotlinx.json.*
import io.ktor.server.plugins.contentnegotiation.*
import kotlinx.serialization.Serializable

@Serializable
data class User(val id: Int, val name: String, val email: String)

fun Application.configureRouting() {
    install(ContentNegotiation) {
        json()
    }
    
    routing {
        get("/api/users") {
            val users = listOf(
                User(1, "John Doe", "[email protected]"),
                User(2, "Jane Smith", "[email protected]")
            )
            call.respond(users)
        }
        
        post("/api/users") {
            val user = call.receive<User>()
            call.respond(user)
        }
    }
}

API Response:

[
  {"id": 1, "name": "John Doe", "email": "[email protected]"},
  {"id": 2, "name": "Jane Smith", "email": "[email protected]"}
]

🔹 Ktor Client Usage

Make HTTP requests with Ktor client:

import io.ktor.client.*
import io.ktor.client.call.*
import io.ktor.client.plugins.contentnegotiation.*
import io.ktor.client.request.*
import io.ktor.serialization.kotlinx.json.*

suspend fun main() {
    val client = HttpClient {
        install(ContentNegotiation) {
            json()
        }
    }
    
    // GET request
    val response: String = client.get("https://api.example.com/data").body()
    println(response)
    
    // POST request
    val user = User(3, "Bob Wilson", "[email protected]")
    val createdUser: User = client.post("https://api.example.com/users") {
        setBody(user)
    }.body()
    
    client.close()
}