Building a Kotlin Multiplatform Library in 10 Minutes.

Why Not?

!! WARNING !!

Viewer Discretion Advised - Live Code Generation Ahead

Zachary Powell

Android Developer Since 2009

Sr Android Developer Advocate

Manager, DevRel at Vonage

@DevWithZachary

Communication and Network APIs

Libraries Libraries Libraries

• Framework SDK's
• Testing
• Dependency Injector
• Networking
• Plus many many more.....

Application Programming Interfaces (APIs)

• Third Party APIs
• Internal APIs

Consuming APIs manually sucks!

• Lacking Libraries
• Missing Documentation
• Time consuming
• Ambiguity

Lets fix that with...

Generating Libraries!

Have you heard of OpenAPI?

Do you use OpenAPI?

What is OpenAPI?

What is OpenAPI?

"The OpenAPI Specification (OAS) defines a standard, language-agnostic interface to HTTP APIs which allows both humans and computers to discover and understand the capabilities of the service without access to source code, documentation, or through network traffic inspection." - https://swagger.io/specification/

What is OpenAPI?

OpenAPI Documents

OpenAPI Documents

Define Objects that Break Down your API Definition

• Meta Data
• Server Infomation
• End points
• Parameters....

JSON

{
  "title": "Sample Pet Store App",
  "summary": "A pet store manager.",
  "termsOfService": "https://example.com/terms/",
  "contact": {
    "name": "API Support",
    "url": "https://www.example.com/support",
    "email": "support@example.com"
  },
  "license": {
    "name": "Apache 2.0",
    "url": "https://www.apache.org/licenses/LICENSE-2.0.html"
  },
  "version": "1.0.1"
}

YAML

title: Sample Pet Store App
summary: A pet store manager.
termsOfService: https://example.com/terms/
contact:
  name: API Support
  url: https://www.example.com/support
  email: support@example.com
license:
  name: Apache 2.0
  url: https://www.apache.org/licenses/LICENSE-2.0.html
version: 1.0.1

But Why?

But Why?

Define an API Contract between those building the API and those using it.

But Why?

The Tooling!

• Documentation
• Mocking
• Security
• Testing
• Code Generation
• openapi.tools

Vonage SMS API

https://developer.vonage.com/en/api/sms

"paths": {
      "/{format}": {
         "post": {
            "operationId": "send-an-sms",
            "summary": "Send an SMS",
            "description": "Send an outbound SMS from your Vonage account",
            "parameters": [
               {
                  "name": "format",
                  "description": "The format of the response",
                  "in": "path",
                  "required": true,
                  "schema": {
                     "example": "json",
                     "type": "string",
                     "enum": [
                        "json",
                        "xml"
                     ],
                     "default": "json"
                  }
               }
            ], ...

OpenAPI Generator

https://openapi-generator.tech/

Servers

ada-server, aspnet-fastendpoints, aspnetcore, cpp-pistache-server, cpp-qt-qhttpengine-server, cpp-restbed-server, cpp-restbed-server-deprecated, csharp-functions, erlang-server,erlang-server-deprecated, fsharp-functions, fsharp-giraffe-server, go-echo-server, go-gin-server, go-server, graphql-nodejs-express-server, haskell, haskell-yesod, java-camel, java-helidon-server, java-inflector, java-micronaut-server, java-microprofile, java-msf4j, java-pkmst, java-play-framework, java-undertow-server, java-vertx, java-vertx-web, java-wiremock, jaxrs-cxf, jaxrs-cxf-cdi, jaxrs-cxf-extended, jaxrs-jersey, jaxrs-resteasy, jaxrs-resteasy-eap, jaxrs-spec, julia-server, kotlin-server, kotlin-spring, kotlin-vertx, kotlin-wiremock, nodejs-express-server, php-flight, php-laravel, php-lumen, php-mezzio-ph, php-slim4, php-symfony, python-aiohttp, python-blueplanet, python-fastapi, python-flask, ruby-on-rails, ruby-sinatra, rust-axum, rust-server, scala-akka-http-server, scala-cask, scala-finch, scala-http4s-server, scala-lagom-server, scala-play-server, scalatra, spring

Clients

ada, android, apex, bash, c, clojure, cpp-qt-client, cpp-restsdk, cpp-tiny, cpp-tizen, cpp-ue4, crystal, csharp, dart, dart-dio, eiffel, elixir, elm, erlang-client, erlang-proper, go, groovy, haskell-http-client, java, javascript, jaxrs-cxf-client, jetbrains-http-client, jmeter, julia-client, k6, kotlin, lua, n4js, nim, objc, ocaml, perl, php, powershell, python, r, ruby, rust, scala, scalaz, swift-combine, swift5, typescript, xojo-client, zapier

Clients

ada, android, apex, bash, c, clojure, cpp-qt-client, cpp-restsdk, cpp-tiny, cpp-tizen, cpp-ue4, crystal, csharp, dart, dart-dio, eiffel, elixir, elm, erlang-client, erlang-proper, go, groovy, haskell-http-client, java, javascript, jaxrs-cxf-client, jetbrains-http-client, jmeter, julia-client, k6, kotlin, lua, n4js, nim, objc, ocaml, perl, php, powershell, python, r, ruby, rust, scala, scalaz, swift-combine, swift5, typescript, xojo-client, zapier

Generate the code

java -jar ../openapi-generator-cli.jar generate
-i ../sms.json
-g kotlin
--additional-properties=library=multiplatform,dateLibrary=kotlinx-datetime

Generate the code

java -jar ../openapi-generator-cli.jar generate
-i ../sms.json
-g kotlin
--additional-properties=library=multiplatform,dateLibrary=kotlinx-datetime

Generate the code

java -jar ../openapi-generator-cli.jar generate
-i ../sms.json
-g kotlin
--additional-properties=library=multiplatform,dateLibrary=kotlinx-datetime

Generate the code

java -jar ../openapi-generator-cli.jar generate
-i ../sms.json
-g kotlin
--additional-properties=library=multiplatform,dateLibrary=kotlinx-datetime

Generate the code

java -jar ../openapi-generator-cli.jar generate
-i ../sms.json
-g kotlin
--additional-properties=library=multiplatform,dateLibrary=kotlinx-datetime

Generate the code!

Photo Break!

Why Not?

Why Not?

Incomplete/Complex OpenAPI specs may not generate as expected

Why Not?

Purely one to one mapping

Why Not?

No additional business logic or helper functions

Why Not?

BUT its a great starting point!

Hand made SDKs here to stay!

Checkout the new Kotlin Server SDK

Coupon Code, €10 free credit: 25DEVW10

https://github.com/Vonage/vonage-kotlin-sdk

Thank you!

links.zpweb.site

github.com/devwithzachary/presentations