Ktor Plugins
Collection of useful Ktor plugins. All plugins are hosted on Maven central and have same version that should be similar to the latest version of Ktor. The plugins can be added to your project as easy as:
implementation("dev.forst", "ktor-<plugin>", "<latest version>")
- ktor-api-key
- simple authentication provider for Ktor that verifies presence of the API key in the header
- ktor-content-security-policy
- plugin that allows setting Content-Security-Policy headers
- ktor-openapi-generator
- generates OpenAPI definitions from your server with support for Ktor
>= 2.0.0 - developed in separate repository because it is a fork of existing project
- generates OpenAPI definitions from your server with support for Ktor
- ktor-rate-limiting
- plugin that enables rate limiting in Ktor
Ktor API Key Authentication Provider
Simple authentication provider for Ktor that verifies presence of the API key in the header. Useful if you want to use X-Api-Key or similar approaches for request authentication.
/**
* Minimal Ktor application with API Key authentication.
*/
fun Application.minimalExample() {
// key that will be used to authenticate requests
val expectedApiKey = "this-is-expected-key"
// principal for the app
data class AppPrincipal(val key: String) : Principal
// now we install authentication feature
install(Authentication) {
// and then api key provider
apiKey {
// set function that is used to verify request
validate { keyFromHeader ->
keyFromHeader
.takeIf { it == expectedApiKey }
?.let { AppPrincipal(it) }
}
}
}
routing {
authenticate {
get {
val p = call.principal<AppPrincipal>()!!
call.respondText("Key: ${p.key}")
}
}
}
}
Ktor Content Security Policy
Plugin that allows setting Content-Security-Policy headers.
/**
* Minimal Ktor application using Content Security Policy.
*/
fun Application.minimalExample() {
install(ContentSecurityPolicy) {
skipWhen { call ->
call.request.path().startsWith("/some-ignored-route")
}
policy(
"default-src" to "'none'"
)
}
}
Ktor OpenAPI Generator & Swagger UI
Ktor OpenAPI plugin (with support for Ktor 2.x.y) that generates OpenAPI from your routes definition and allows you to host Swagger UI. Hosted on different repository: LukasForst/ktor-openapi-generator as it is a fork of popular papsign/Ktor-OpenAPI-Generator with some refactoring and support for Ktor 2.x.y.
It supports most of the stuff from Ktor including JWT and Session auth.
/**
* Minimal example of OpenAPI plugin for Ktor.
*/
fun Application.minimalExample() {
// install OpenAPI plugin
install(OpenAPIGen) {
// this automatically servers Swagger UI on /swagger-ui
serveSwaggerUi = true
info {
title = "Minimal Example API"
}
}
// install JSON support
install(ContentNegotiation) {
jackson()
}
// add basic routes for openapi.json and redirect to UI
routing {
// serve openapi.json
get("/openapi.json") {
call.respond(this@routing.application.openAPIGen.api.serialize())
}
// and do redirect to make it easier to remember
get("/swagger-ui") {
call.respondRedirect("/swagger-ui/index.html?url=/openapi.json", true)
}
}
// and now example routing
apiRouting {
route("/example/{name}") {
// SomeParams are parameters (query or path), SomeResponse is what the backend returns and SomeRequest
// is what was passed in the body of the request
post<SomeParams, SomeResponse, SomeRequest> { params, someRequest ->
respond(SomeResponse(bar = "Hello ${params.name}! From body: ${someRequest.foo}."))
}
}
}
}
data class SomeParams(@PathParam("who to say hello") val name: String)
data class SomeRequest(val foo: String)
data class SomeResponse(val bar: String)
Ktor Rate Limiting
A simple library that enables Rate Limiting in Ktor.
/**
* Minimal Ktor application with Rate Limiting enabled.
*/
fun Application.minimalExample() {
// install feature
install(RateLimiting) {
registerLimit(
// allow 10 requests
limit = 10,
// each 1 minute
window = Duration.ofMinutes(1)
) {
// use host as a key to determine who is who
call.request.origin.host
}
// and exclude path which ends with "excluded"
excludeRequestWhen {
call.request.path().endsWith("excluded")
}
}
// now add some routes
routing {
get {
call.respondText("Hello ${call.request.origin.host}")
}
get("excluded") {
call.respondText("Hello ${call.request.origin.host}")
}
}
}
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