Сервер авторизации Spring Boot Oauth 2.0 возвращает нулевой токен

Question

Я пытаюсь понять Oauth 2.0, и я пытался следовать простому руководству, но я не понимаю, что не так с моим кодом. В основном сервер авторизации не возвращает никакого токена клиенту, и я непонять почему :( Вот код: ResourceServer App: AuthorizationServerConfig:

@Configuration
@EnableAuthorizationServer
public class AuthorizationServerConfig extends AuthorizationServerConfigurerAdapter {

    @Override
    public void configure(ClientDetailsServiceConfigurer clients) throws Exception {
        clients.inMemory().withClient("javainuse").secret("secret").authorizedGrantTypes("authorization_code")
            .scopes("read").authorities("CLIENT").redirectUris("http://localhost:8090/showEmployees");
    }

}

EmployeeSecurityConfiguration:

@Configuration
@EnableWebSecurity
public class EmployeeSecurityConfiguration extends WebSecurityConfigurerAdapter {

    @Override
    public void configure(WebSecurity web) throws Exception {
        web.ignoring().antMatchers("/resources/**");
    }

    @Override
    protected void configure(HttpSecurity http) throws Exception {
        http.authorizeRequests().antMatchers("/").permitAll().antMatchers("/user/getEmployeesList").hasAnyRole("ADMIN")
                .anyRequest().authenticated().and().formLogin().permitAll().and().logout().permitAll();

        http.csrf().disable();
    }

    @Override
    public void configure(AuthenticationManagerBuilder authenticationMgr) throws Exception {
        authenticationMgr.inMemoryAuthentication().passwordEncoder(NoOpPasswordEncoder.getInstance()).withUser("admin").password("admin").authorities("ROLE_ADMIN");
    }
}

ResourceServer:

@Configuration
@EnableResourceServer
public class ResourceServer extends ResourceServerConfigurerAdapter {

    @Override
    public void configure(HttpSecurity http) throws Exception {
        http.requestMatchers().antMatchers("/user/getEmployeesList/**").and().authorizeRequests().anyRequest()
                .access("#oauth2.hasScope('read')");
    }
}

EmployeeController:

@Controller
public class EmployeeController {

    @RequestMapping(value = "/user/getEmployeesList", produces ="application/json")
    @ResponseBody
    public List<Employee> getEmployeeList(){
        List<Employee> employees = new ArrayList<>();
        Employee emp = new Employee();
        emp.setEmpId("emp1");
        emp.setEmpName("emp1");
        employees.add(emp);
        return employees;
    }

}

И клиентское приложение:

@Controller
public class EmployeeController {

    @RequestMapping(value = "/getEmployees", method = RequestMethod.GET)
    public ModelAndView getEmployeeInfo() {
        return new ModelAndView("getEmployees");
    }

    @RequestMapping(value = "/showEmployees", method = RequestMethod.GET)
    public ModelAndView showEmployees(@RequestParam("code") String code) throws JsonProcessingException, IOException {
        ResponseEntity<String> response = null;
        System.out.println("Authorization Code------" + code);

        RestTemplate restTemplate = new RestTemplate();

        // According OAuth documentation we need to send the client id and secret key in the header for authentication
        String credentials = "javainuse:secret";
        String encodedCredentials = new String(Base64.encodeBase64(credentials.getBytes()));

        HttpHeaders headers = new HttpHeaders();
        headers.setAccept(Arrays.asList(MediaType.APPLICATION_JSON));
        headers.add("Authorization", "Basic " + encodedCredentials);

        HttpEntity<String> request = new HttpEntity<String>(headers);

        String access_token_url = "http://localhost:8080/oauth/token";
        access_token_url += "?code=" + code;
        access_token_url += "&grant_type=authorization_code";
        access_token_url += "&redirect_uri=http://localhost:8090/showEmployees";

        response = restTemplate.exchange(access_token_url, HttpMethod.POST, request, String.class);

        System.out.println("Access Token Response ---------" + response.getBody());
        return null;

    }
}

Sysout, который показывает response.getBody () всегда нулевой, и я понятия не имею, почему это происходит