kotlin-ktor-patterns

name	kotlin-ktor-patterns
description	Ktor server patterns including routing DSL, plugins, authentication, Koin DI, kotlinx.serialization, WebSockets, and testApplication testing.
origin	ECC

Ktor Server Patterns

Comprehensive Ktor patterns for building robust, maintainable HTTP servers with Kotlin coroutines.

When to Activate

• Building Ktor HTTP servers
• Configuring Ktor plugins (Auth, CORS, ContentNegotiation, StatusPages)
• Implementing REST APIs with Ktor
• Setting up dependency injection with Koin
• Writing Ktor integration tests with testApplication

Application Structure

src/main/kotlin/
├── com/example/
│   ├── Application.kt
│   ├── plugins/
│   │   ├── Routing.kt
│   │   ├── Serialization.kt
│   │   ├── Authentication.kt
│   │   └── StatusPages.kt
│   ├── routes/
│   ├── models/
│   ├── services/
│   ├── repositories/
│   └── di/

Routing DSL

fun Route.userRoutes() {
    val userService by inject<UserService>()

    route("/users") {
        get {
            val users = userService.getAll()
            call.respond(users)
        }

        get("/{id}") {
            val id = call.parameters["id"]
                ?: return@get call.respond(HttpStatusCode.BadRequest, "Missing id")
            val user = userService.getById(id)
                ?: return@get call.respond(HttpStatusCode.NotFound)
            call.respond(user)
        }

        post {
            val request = call.receive<CreateUserRequest>()
            val user = userService.create(request)
            call.respond(HttpStatusCode.Created, user)
        }
    }
}

Status Pages (Error Handling)

fun Application.configureStatusPages() {
    install(StatusPages) {
        exception<IllegalArgumentException> { call, cause ->
            call.respond(HttpStatusCode.BadRequest, ApiResponse.error<Unit>(cause.message ?: "Bad request"))
        }
        exception<Throwable> { call, cause ->
            call.application.log.error("Unhandled exception", cause)
            call.respond(HttpStatusCode.InternalServerError, ApiResponse.error<Unit>("Internal server error"))
        }
    }
}

testApplication Testing

class UserRoutesTest : FunSpec({
    test("GET /users returns list of users") {
        testApplication {
            application {
                install(Koin) { modules(testModule) }
                configureSerialization()
                configureRouting()
            }
            val response = client.get("/users")
            response.status shouldBe HttpStatusCode.OK
        }
    }
})

Quick Reference

Pattern	Description
route("/path") { get { } }	Route grouping with DSL
call.receive<T>()	Deserialize request body
call.respond(status, body)	Send response with status
by inject<T>()	Koin dependency injection
testApplication { }	Integration testing