Sign in with Slack (OpenID Connect) Example App in Kotlin

app-manifest.yml

_metadata:
  major_version: 1
  minor_version: 1
display_information:
  name: my-openid-connect-app
oauth_config:
  redirect_urls:
    - https://{your-domain-here}/slack/oauth_redirect
  scopes:
    user:
      - openid
      - email
      - profile

build.gradle

plugins {
  id("org.jetbrains.kotlin.jvm") version "1.5.21"
  id("application")
}
repositories {
  mavenCentral()
}
dependencies {
  implementation(platform("org.jetbrains.kotlin:kotlin-bom"))
  implementation("org.jetbrains.kotlin:kotlin-stdlib-jdk8")
  implementation("com.slack.api:bolt-jetty:1.10.0-RC1")
  implementation("com.auth0:java-jwt:3.18.1")
  implementation("org.slf4j:slf4j-simple:1.7.32") // or logback-classic
}
application {
  mainClassName = "MyAppKt" // add "Kt" suffix for main function source file
}

MyApp.kt

import com.auth0.jwt.JWT
import com.slack.api.Slack
import com.slack.api.bolt.App
import com.slack.api.bolt.jetty.SlackAppServer

fun main() {
  System.setProperty("org.slf4j.simpleLogger.log.com.slack.api", "debug")

  // export SLACK_CLIENT_ID=
  // export SLACK_CLIENT_SECRET=
  // export SLACK_USER_SCOPES=openid,email,profile
  // export SLACK_INSTALL_PATH=install
  // export SLACK_REDIRECT_URI_PATH=oauth_redirect
  // export SLACK_REDIRECT_URI=https://{your-domain-here}/slack/oauth_redirect
  val app = App().asOpenIDConnectApp(true)
  val slack = Slack.getInstance()

  app.openIDConnectSuccess { request, response, token ->
    val logger = request.context.logger
    val claims = JWT.decode(token.idToken).claims
    logger.info("id_token claims: {}", claims)

    // Store the data in your database

    // Example demonstrating openid.connect.userInfo API call with the issued access token
    val teamId = claims["https://slack.com/team_id"]?.asString()
    val userInfo = slack.methods(token.accessToken, teamId).openIDConnectUserInfo { it }
    logger.info("usersInfo: {}", userInfo)

    // Example demonstrating how to refresh the token afterwards
    if (token.refreshToken != null) {
      // refreshing the access token for the first time
      val refreshedToken = slack.methods(null, teamId).openIDConnectToken { it
        .clientId(System.getenv("SLACK_CLIENT_ID"))
        .clientSecret(System.getenv("SLACK_CLIENT_SECRET"))
        .grantType("refresh_token")
        .refreshToken(token.refreshToken)
      }
      val userInfo = slack.methods(refreshedToken.accessToken, teamId).openIDConnectUserInfo { it }
      logger.info("usersInfo by a refreshed token: {}", userInfo)
    }

    // Redirect the user to the next step
    response.statusCode = 302
    response.headers["Location"] = listOf("https://slack.com/")
    response
  }

  val apps = mutableMapOf(
    "/slack/" to app
  )
  val server = SlackAppServer(apps)
  server.start() // http://localhost:3000/slack/install
}