An OAuth authorization service built using Kotlin

KotlinAuthenticationServiceApplication.kt

// org.springframework.cloud:spring-cloud-starter-oauth2
// org.springframework.boot:spring-boot-starter-data-jpa
// com.h2database:h2 
// redefine: spring-security.version == 4.1.0.RELEASE

package com.example

import org.springframework.beans.factory.annotation.Autowired
import org.springframework.boot.CommandLineRunner
import org.springframework.boot.SpringApplication
import org.springframework.boot.autoconfigure.SpringBootApplication
import org.springframework.context.annotation.Bean
import org.springframework.data.jpa.repository.JpaRepository
import org.springframework.security.authentication.AuthenticationManager
import org.springframework.security.core.authority.AuthorityUtils
import org.springframework.security.core.userdetails.User
import org.springframework.security.core.userdetails.UserDetailsService
import org.springframework.security.core.userdetails.UsernameNotFoundException
import org.springframework.security.oauth2.config.annotation.configurers.ClientDetailsServiceConfigurer
import org.springframework.security.oauth2.config.annotation.web.configuration.AuthorizationServerConfigurerAdapter
import org.springframework.security.oauth2.config.annotation.web.configuration.EnableAuthorizationServer
import org.springframework.security.oauth2.config.annotation.web.configuration.EnableResourceServer
import org.springframework.security.oauth2.config.annotation.web.configurers.AuthorizationServerEndpointsConfigurer
import org.springframework.web.bind.annotation.RequestMapping
import org.springframework.web.bind.annotation.RestController
import java.security.Principal
import java.util.*
import java.util.stream.Stream
import javax.persistence.Entity
import javax.persistence.GeneratedValue
import javax.persistence.Id

@EnableResourceServer
@EnableAuthorizationServer
@SpringBootApplication
@RestController
open class KotlinAuthenticationServiceApplication :
        AuthorizationServerConfigurerAdapter() {

    @Autowired
    lateinit var authenticationManager: AuthenticationManager

    @Bean
    open fun userDetailsService(accountRepository: AccountRepository) = UserDetailsService {
        username ->
            accountRepository.findByUsername(username)
                .map { account ->
                    User (account.username,
                            account.password,
                            account.active,
                            account.active,
                            account.active,
                            account.active,
                            AuthorityUtils.createAuthorityList("SCOPE_READ",
                                    "SCOPE_ADMIN"))
                }
                .orElseThrow {
                    UsernameNotFoundException (
                            "couldn't find the user ${username}!")
                }
    }

    @Bean
    open fun sampleDataCLR(accountRepository: AccountRepository): CommandLineRunner =
        CommandLineRunner {
            Stream.of("jlong,spring", "pwebb,boot", "dsyer,cloud")
                .map { s -> s.split(",") }
                .forEach { tuple ->
                    accountRepository.save(
                            Account(tuple[0], tuple[1], true))
                }
        }

    override fun configure(clients: ClientDetailsServiceConfigurer?) {
        clients
                ?.inMemory()
                ?.withClient("acme")
                ?.secret("acmesecret")
                ?.authorizedGrantTypes("password")
                ?.scopes("openid")
    }

    override fun configure(endpoints: AuthorizationServerEndpointsConfigurer?) {
        endpoints?.authenticationManager(this.authenticationManager)
    }

    @RequestMapping ("/user")
    open fun user(principal: Principal) = principal

}

fun main(args: Array<String>) {
    SpringApplication.run(KotlinAuthenticationServiceApplication::class.java, *args)
}

interface AccountRepository : JpaRepository <Account, Long> {

    fun findByUsername(username: String): Optional <Account>
}

@Entity
open class Account(var username: String ? = null,
                   var password: String ? = null,
                   var active: Boolean = false) {

    constructor() : this(null, null, false)

    @Id
    @GeneratedValue
    var id: Long = 0
}