An OAuth authorization service built using Java

AuthServiceApplication.java

// 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 javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import java.security.Principal;
import java.util.Optional;
import java.util.stream.Stream;

@EnableResourceServer
@SpringBootApplication
@RestController
@EnableAuthorizationServer
public class AuthServiceApplication extends AuthorizationServerConfigurerAdapter {
	@Bean
	CommandLineRunner commandLineRunner(AccountRepository accountRepository) {
		return args ->
				Stream.of("apoutsma,reactive", "jlong,spring", "pwebb,boot", "dsyer,cloud")
						.map(x -> x.split(","))
						.forEach(t -> accountRepository.save(new Account(t[0], t[1])));
	}

	@Autowired
	private AuthenticationManager authenticationManager;

	public static void main(String[] args) {
		SpringApplication.run(AuthServiceApplication.class, args);
	}

	@RequestMapping("/user")
	Principal principal(Principal principal) {
		return principal;
	}

	@Override
	public void configure(ClientDetailsServiceConfigurer clients) throws Exception {
		clients
				.inMemory()
				.withClient("acme")
				.secret("acmesecret")
				.authorizedGrantTypes("password")
				.scopes("openid");
	}

	@Override
	public void configure(AuthorizationServerEndpointsConfigurer endpoints) throws Exception {
		endpoints
				.authenticationManager(this.authenticationManager);
	}

	@Bean
	UserDetailsService userDetailsService(AccountRepository accountRepository) {
		return username ->
				accountRepository.findByUsername(username)
						.map(account -> new User(
								account.getUsername(),
								account.getPassword(),
								true, true, true, true,
								AuthorityUtils.createAuthorityList("SCOPE_READ", "SCOPE_ADMIN")
						))
						.orElseThrow(() -> new UsernameNotFoundException(
								String.format("couldn't find %s!", username)));

	}
}

interface AccountRepository extends JpaRepository<Account, Long> {

	Optional<Account> findByUsername(String username);
}

@Entity
class Account {

	public Account(String username, String password) {
		this.username = username;
		this.password = password;
	}

	@Override
	public String toString() {
		return "Account{" +
				"id=" + id +
				", username='" + username + '\'' +
				", password='" + password + '\'' +
				'}';
	}

	Account() { // why JPA why
	}

	@Id
	@GeneratedValue
	private Long id;
	private String username, password;

	public Long getId() {
		return id;
	}

	public String getUsername() {
		return username;
	}

	public String getPassword() {
		return password;
	}
}