<!-- Configure Authentication mechanism -->
<authentication-manager alias="authenticationManager">
    <authentication-provider ref="oAuth2AuthenticationProvider"/>
</authentication-manager>


<beans:bean id="oAuth2AuthenticationProvider" class="my.custom.Oauth2AuthenticationProvider">
    <beans:constructor-arg name="accessTokenUri" value="http://x.x.x.x/oauth/token"/>
    <beans:constructor-arg name="clientId" value="myClientId"/>
    <beans:constructor-arg name="clientSecret" value="myClientSecret"/>
    <beans:constructor-arg name="scope">
        <beans:list>
            <beans:value>myScope</beans:value>
        </beans:list>
    </beans:constructor-arg>
</beans:bean>

<beans:bean id="resourceOwnerPasswordAccessTokenProvider" class="org.springframework.security.oauth2.client.token.grant.password.ResourceOwnerPasswordAccessTokenProvider"/>

public class Oauth2AuthenticationProvider implements AuthenticationProvider {

@Autowired
private ResourceOwnerPasswordAccessTokenProvider provider;

private String accessTokenUri;
private String clientId;
private String clientSecret;
private List<String> scope;

public Oauth2AuthenticationProvider(String accessTokenUri, String clientId, String clientSecret, List<String> scope) {
    this.accessTokenUri = accessTokenUri;
    this.clientId = clientId;
    this.clientSecret = clientSecret;
    this.scope = scope;
}

@Override
public Authentication authenticate(Authentication authentication) throws AuthenticationException {
    String username = authentication.getName();
    String password = authentication.getCredentials().toString();
    OAuth2AccessToken token = obtainToken(username, password);
    return handleLogonSuccess(authentication, token);
}

private OAuth2AccessToken obtainToken(String username, String password) {
    ResourceOwnerPasswordResourceDetails passwordResourceDetails = new ResourceOwnerPasswordResourceDetails();
    passwordResourceDetails.setUsername(username);
    passwordResourceDetails.setPassword(password);
    passwordResourceDetails.setClientId(clientId);
    passwordResourceDetails.setClientSecret(clientSecret);
    passwordResourceDetails.setScope(scope);
    passwordResourceDetails.setAccessTokenUri(accessTokenUri);
    DefaultAccessTokenRequest defaultAccessTokenRequest = new DefaultAccessTokenRequest();
    OAuth2AccessToken token;
    try {
        token = provider.obtainAccessToken(passwordResourceDetails, defaultAccessTokenRequest);
    } catch (OAuth2AccessDeniedException accessDeniedException) {
        throw new BadCredentialsException("Invalid credentials", accessDeniedException);
    }

    return token;
}

public OAuth2AccessToken refreshToken(OAuth2AuthenticationToken authentication) {
    OAuth2AccessToken token = authentication.getoAuth2AccessToken();
    OAuth2RefreshToken refreshToken = token.getRefreshToken();
    BaseOAuth2ProtectedResourceDetails resourceDetails = new BaseOAuth2ProtectedResourceDetails();
    resourceDetails.setClientId(clientId);
    resourceDetails.setClientSecret(clientSecret);
    resourceDetails.setScope(scope);
    resourceDetails.setAccessTokenUri(accessTokenUri);
    OAuth2AccessToken newToken = provider.refreshAccessToken(resourceDetails, refreshToken, new DefaultAccessTokenRequest());
    authentication.setoAuth2AccessToken(newToken);
    return newToken;
}

public boolean supports(Class<?> authentication) {
    return UsernamePasswordAuthenticationToken.class.isAssignableFrom(authentication);
}

private Authentication handleLogonSuccess(Authentication authentication, OAuth2AccessToken token) {

    MyCustomOAuth2AuthenticationToken successAuthenticationToken = new MyCustomOAuth2AuthenticationToken(user, authentication.getCredentials(), calculateAuthorities(authentication), token);

    return successAuthenticationToken;
}

public list<GrantedAuthority> calculateAuthorities(Authentication authentication) {
        //my custom logic that assigns the correct role. e.g. ROLE_USER
}

@Configuration
@EnableOAuth2Client
public class RestClientConfig {

    @Value("${http.client.maxPoolSize}")
    private Integer maxPoolSize;

    @Value("${oauth2.resourceId}")
    private String resourceId;

    @Value("${oauth2.clientId}")
    private String clientId;

    @Value("${oauth2.clientSecret}")
    private String clientSecret;

    @Value("${oauth2.accessTokenUri}")
    private String accessTokenUri;


    @Autowired
    private OAuth2ClientContext oauth2ClientContext;


    @Bean
    public ClientHttpRequestFactory httpRequestFactory() {
        return new HttpComponentsClientHttpRequestFactory(httpClient());
    }

    @Bean
    public HttpClient httpClient() {
        PoolingHttpClientConnectionManager connectionManager = new PoolingHttpClientConnectionManager();
        connectionManager.setMaxTotal(maxPoolSize);
        // This client is for internal connections so only one route is expected
        connectionManager.setDefaultMaxPerRoute(maxPoolSize);
        return HttpClientBuilder.create().setConnectionManager(connectionManager).build();
    }

    @Bean
    public OAuth2ProtectedResourceDetails oauth2ProtectedResourceDetails() {
        ResourceOwnerPasswordResourceDetails details = new ResourceOwnerPasswordResourceDetails();
        details.setId(resourceId);
        details.setClientId(clientId);
        details.setClientSecret(clientSecret);
        details.setAccessTokenUri(accessTokenUri);
        return details;
    }

    @Bean
    public AccessTokenProvider accessTokenProvider() {
        ResourceOwnerPasswordAccessTokenProvider tokenProvider = new ResourceOwnerPasswordAccessTokenProvider();
        tokenProvider.setRequestFactory(httpRequestFactory());
        return new AccessTokenProviderChain(
                  Arrays.<AccessTokenProvider> asList(tokenProvider)
                );
    }

    @Bean
    public OAuth2RestTemplate restTemplate() {
        OAuth2RestTemplate template = new OAuth2RestTemplate(oauth2ProtectedResourceDetails(), oauth2ClientContext);
        template.setRequestFactory(httpRequestFactory());
        template.setAccessTokenProvider(accessTokenProvider());
        return template;
    }
}

@Autowired
private OAuth2RestTemplate restTemplate;

restTemplate.getOAuth2ClientContext().getAccessTokenRequest().set("username", username);
restTemplate.getOAuth2ClientContext().getAccessTokenRequest().set("password", password);

String url = "http://localhost:{port}/api/users/search/findByUsername?username={username}";

    ResponseEntity<User> responseEntity = restTemplate.getForEntity(
            url, User.class, 8081, username);