public class RestAuthenticationEntryPoint implements AuthenticationEntryPoint {

    @Override
    public void commence(
            HttpServletRequest request,
            HttpServletResponse response,
            AuthenticationException authException) throws IOException {
        response.sendError(HttpServletResponse.SC_UNAUTHORIZED, authException.getMessage());
    }
}

@Path("/auth")
public class AuthEndpoint extends EndpointBase {

...

    @GET
    @Path("/login")
    public Response authorize(@QueryParam(REDIRECT_URI) String redirectUri) {
        String authUri = "/oauth2/authorization/bitbucket";
        UriComponentsBuilder builder = fromPath(authUri).queryParam(REDIRECT_URI, redirectUri);
        return handle(() -> temporaryRedirect(builder.build().toUri()).build());
    }
}

public class ExampleAuthenticationSuccessHandler extends SimpleUrlAuthenticationSuccessHandler {

    private final TokenService tokenService;

    private final AuthProperties authProperties;

    private final HttpCookieOAuth2AuthorizationRequestRepository authorizationRequestRepository;

    public ExampleAuthenticationSuccessHandler(
            TokenService tokenService,
            AuthProperties authProperties,
            HttpCookieOAuth2AuthorizationRequestRepository authorizationRequestRepository) {
        this.tokenService = requireNonNull(tokenService);
        this.authProperties = requireNonNull(authProperties);
        this.authorizationRequestRepository = requireNonNull(authorizationRequestRepository);
    }

    @Override
    public void onAuthenticationSuccess(HttpServletRequest request, HttpServletResponse response, Authentication authentication) throws IOException, ServletException {
        log.info("Logged in user {}", authentication.getPrincipal());
        super.onAuthenticationSuccess(request, response, authentication);
    }

    @Override
    protected String determineTargetUrl(HttpServletRequest request, HttpServletResponse response, Authentication authentication) {
        Optional<String> redirectUri = getCookie(request, REDIRECT_URI).map(Cookie::getValue);

        if (redirectUri.isPresent() && !isAuthorizedRedirectUri(redirectUri.get())) {
            throw new BadRequestException("Received unauthorized redirect URI.");
        }

        return UriComponentsBuilder.fromUriString(redirectUri.orElse(getDefaultTargetUrl()))
                .queryParam("token", tokenService.newAccessToken(toUserContext(authentication)))
                .build().toUriString();
    }

    @Override
    protected void handle(HttpServletRequest request, HttpServletResponse response, Authentication authentication) throws IOException {
        redirectToTargetUrl(request, response, authentication);
    }

    private boolean isAuthorizedRedirectUri(String uri) {
        URI clientRedirectUri = URI.create(uri);
        return authProperties.getAuthorizedRedirectUris()
                .stream()
                .anyMatch(authorizedRedirectUri -> {
                    // Only validate host and port. Let the clients use different paths if they want to.
                    URI authorizedURI = URI.create(authorizedRedirectUri);
                    return authorizedURI.getHost().equalsIgnoreCase(clientRedirectUri.getHost())
                            && authorizedURI.getPort() == clientRedirectUri.getPort();
                });
    }

    private TokenService.UserContext toUserContext(Authentication authentication) {
        ExampleOAuth2User principal = (ExampleOAuth2User) authentication.getPrincipal();
        return TokenService.UserContext.builder()
                .login(principal.getName())
                .name(principal.getFullName())
                .build();
    }

    private void addRefreshTokenCookie(HttpServletResponse response, Authentication authentication) {
        RefreshToken token = tokenService.newRefreshToken(toUserContext(authentication));
        addCookie(response, REFRESH_TOKEN, token.getId(), (int) token.getValiditySeconds());
    }

    private void redirectToTargetUrl(HttpServletRequest request, HttpServletResponse response, Authentication authentication) throws IOException {
        String targetUrl = determineTargetUrl(request, response, authentication);

        if (response.isCommitted()) {
            logger.debug("Response has already been committed. Unable to redirect to " + targetUrl);
            return;
        }

        addRefreshTokenCookie(response, authentication);
        authorizationRequestRepository.removeAuthorizationRequestCookies(request, response);
        getRedirectStrategy().sendRedirect(request, response, targetUrl);
    }
}

public class ExampleAuthenticationFailureHandler implements AuthenticationFailureHandler {

    private final RedirectStrategy redirectStrategy = new DefaultRedirectStrategy();

    private final HttpCookieOAuth2AuthorizationRequestRepository authorizationRequestRepository;

    public ExampleAuthenticationFailureHandler(
            HttpCookieOAuth2AuthorizationRequestRepository authorizationRequestRepository) {
        this.authorizationRequestRepository = requireNonNull(authorizationRequestRepository);
    }

    @Override
    public void onAuthenticationFailure(HttpServletRequest request, HttpServletResponse response, AuthenticationException exception) throws IOException {
        String targetUrl = getFailureUrl(request, exception);
        authorizationRequestRepository.removeAuthorizationRequestCookies(request, response);
        redirectStrategy.sendRedirect(request, response, targetUrl);
    }

    private String getFailureUrl(HttpServletRequest request, AuthenticationException exception) {
        String targetUrl = getCookie(request, Cookies.REDIRECT_URI)
                .map(Cookie::getValue)
                .orElse(("/"));

        return UriComponentsBuilder.fromUriString(targetUrl)
                .queryParam("error", exception.getLocalizedMessage())
                .build().toUriString();
    }
}

public class TokenAuthenticationFilter extends OncePerRequestFilter {

    private final UserService userService;

    private final TokenService tokenService;

    public TokenAuthenticationFilter(
            UserService userService, TokenService tokenService) {
        this.userService = requireNonNull(userService);
        this.tokenService = requireNonNull(tokenService);
    }

    @Override
    protected void doFilterInternal(@NotNull HttpServletRequest request, @NotNull HttpServletResponse response, @NotNull FilterChain chain) throws ServletException, IOException {
        try {
            Optional<String> jwtOpt = getJwtFromRequest(request);
            if (jwtOpt.isPresent()) {
                String jwt = jwtOpt.get();
                if (isNotEmpty(jwt) && tokenService.isValidAccessToken(jwt)) {
                    String login = tokenService.getUsername(jwt);
                    Optional<User> userOpt = userService.findByLogin(login);
                    if (userOpt.isPresent()) {
                        User user = userOpt.get();
                        ExampleOAuth2User oAuth2User = new ExampleOAuth2User(user);
                        OAuth2AuthenticationToken authentication = new OAuth2AuthenticationToken(oAuth2User, oAuth2User.getAuthorities(), oAuth2User.getProvider());
                        authentication.setDetails(new WebAuthenticationDetailsSource().buildDetails(request));

                        SecurityContextHolder.getContext().setAuthentication(authentication);
                    }
                }
            }
        } catch (Exception e) {
            logger.error("Could not set user authentication in security context", e);
        }

        chain.doFilter(request, response);
    }

    private Optional<String> getJwtFromRequest(HttpServletRequest request) {
        String token = request.getHeader(AUTHORIZATION);
        if (isNotEmpty(token) && token.startsWith("Bearer ")) {
            token = token.substring(7);
        }
        return Optional.ofNullable(token);
    }
}

@Path("/auth")
public class AuthEndpoint extends EndpointBase {

...

    @POST
    @Path("/token")
    @Produces(APPLICATION_JSON)
    public Response refreshToken(@CookieParam(REFRESH_TOKEN) String refreshToken) {
        return handle(() -> {
            if (refreshToken == null) {
                throw new InvalidTokenException("Refresh token was not provided.");
            }
            RefreshToken oldRefreshToken = tokenService.findRefreshToken(refreshToken);
            if (oldRefreshToken == null || !tokenService.isValidRefreshToken(oldRefreshToken)) {
                throw new InvalidTokenException("Refresh token is not valid or expired.");
            }

            Map<String, String> result = new HashMap<>();
            result.put("token", tokenService.newAccessToken(of(oldRefreshToken.getUser())));

            RefreshToken newRefreshToken = newRefreshTokenFor(oldRefreshToken.getUser());
            return Response.ok(result).cookie(createRefreshTokenCookie(newRefreshToken)).build();
        });
    }
}

public class HttpCookieOAuth2AuthorizationRequestRepository implements AuthorizationRequestRepository<OAuth2AuthorizationRequest> {

    private static final int COOKIE_EXPIRE_SECONDS = 180;

    private static final String OAUTH2_AUTHORIZATION_REQUEST_COOKIE_NAME = "OAUTH2-AUTH-REQUEST";

    @Override
    public OAuth2AuthorizationRequest loadAuthorizationRequest(HttpServletRequest request) {
        return getCookie(request, OAUTH2_AUTHORIZATION_REQUEST_COOKIE_NAME)
                .map(cookie -> deserialize(cookie, OAuth2AuthorizationRequest.class))
                .orElse(null);
    }

    @Override
    public void saveAuthorizationRequest(OAuth2AuthorizationRequest authorizationRequest, HttpServletRequest request, HttpServletResponse response) {
        if (authorizationRequest == null) {
            removeAuthorizationRequestCookies(request, response);
            return;
        }

        addCookie(response, OAUTH2_AUTHORIZATION_REQUEST_COOKIE_NAME, serialize(authorizationRequest), COOKIE_EXPIRE_SECONDS);
        String redirectUriAfterLogin = request.getParameter(QueryParams.REDIRECT_URI);
        if (isNotBlank(redirectUriAfterLogin)) {
            addCookie(response, REDIRECT_URI, redirectUriAfterLogin, COOKIE_EXPIRE_SECONDS);
        }
    }

    @Override
    public OAuth2AuthorizationRequest removeAuthorizationRequest(HttpServletRequest request) {
        return loadAuthorizationRequest(request);
    }

    public void removeAuthorizationRequestCookies(HttpServletRequest request, HttpServletResponse response) {
        deleteCookie(request, response, OAUTH2_AUTHORIZATION_REQUEST_COOKIE_NAME);
        deleteCookie(request, response, REDIRECT_URI);
    }

    private static String serialize(Object object) {
        return Base64.getUrlEncoder().encodeToString(SerializationUtils.serialize(object));
    }

    @SuppressWarnings("SameParameterValue")
    private static <T> T deserialize(Cookie cookie, Class<T> clazz) {
        return clazz.cast(SerializationUtils.deserialize(Base64.getUrlDecoder().decode(cookie.getValue())));
    }
}

@Configuration
@EnableWebSecurity
public static class WebSecurityConfig extends WebSecurityConfigurerAdapter {

    private final ExampleOAuth2UserService userService;

    private final TokenAuthenticationFilter tokenAuthenticationFilter;

    private final AuthenticationFailureHandler authenticationFailureHandler;

    private final AuthenticationSuccessHandler authenticationSuccessHandler;

    private final HttpCookieOAuth2AuthorizationRequestRepository authorizationRequestRepository;

    @Autowired
    public WebSecurityConfig(
            ExampleOAuth2UserService userService,
            TokenAuthenticationFilter tokenAuthenticationFilter,
            AuthenticationFailureHandler authenticationFailureHandler,
            AuthenticationSuccessHandler authenticationSuccessHandler,
            HttpCookieOAuth2AuthorizationRequestRepository authorizationRequestRepository) {
        this.userService = userService;
        this.tokenAuthenticationFilter = tokenAuthenticationFilter;
        this.authenticationFailureHandler = authenticationFailureHandler;
        this.authenticationSuccessHandler = authenticationSuccessHandler;
        this.authorizationRequestRepository = authorizationRequestRepository;
    }

    @Override
    protected void configure(HttpSecurity http) throws Exception {
        http
                .cors().and()
                .csrf().disable()
                .formLogin().disable()
                .httpBasic().disable()
                .sessionManagement(sm -> sm.sessionCreationPolicy(STATELESS))
                .exceptionHandling(eh -> eh
                        .authenticationEntryPoint(new RestAuthenticationEntryPoint())
                )
                .authorizeRequests(authorizeRequests -> authorizeRequests
                        .antMatchers("/auth/**").permitAll()
                        .anyRequest().authenticated()
                )
                .oauth2Login(oauth2Login -> oauth2Login
                        .failureHandler(authenticationFailureHandler)
                        .successHandler(authenticationSuccessHandler)
                        .userInfoEndpoint(userInfoEndpoint -> userInfoEndpoint.userService(userService))
                        .authorizationEndpoint(authEndpoint -> authEndpoint.authorizationRequestRepository(authorizationRequestRepository))
                );

        http.addFilterBefore(tokenAuthenticationFilter, UsernamePasswordAuthenticationFilter.class);
    }
}

@Path("/api")
public class ApiEndpoint extends EndpointBase {

    @Autowired
    private BitbucketService bitbucketService;

    @GET
    @Path("/repositories")
    @Produces(APPLICATION_JSON)
    public List<Repository> getRepositories() {
        return handle(bitbucketService::getRepositories);
    }
}

public class BitbucketServiceImpl implements BitbucketService {

    private static final String BASE_URL = "https://api.bitbucket.org";

    private final Supplier<RestTemplate> restTemplate;

    public BitbucketServiceImpl(Supplier<RestTemplate> restTemplate) {
        this.restTemplate = restTemplate;
    }

    @Override
    public List<Repository> getRepositories() {
        UriComponentsBuilder uriBuilder = fromHttpUrl(format("%s/2.0/repositories", BASE_URL));
        uriBuilder.queryParam("role", "member");

        ResponseEntity<BitbucketRepositoriesResponse> response = restTemplate.get().exchange(
                uriBuilder.toUriString(),
                HttpMethod.GET,
                new HttpEntity<>(new HttpHeadersBuilder()
                        .acceptJson()
                        .build()),
                BitbucketRepositoriesResponse.class);

        BitbucketRepositoriesResponse body = response.getBody();
        return body == null ? emptyList() : extractRepositories(body);
    }

    private List<Repository> extractRepositories(BitbucketRepositoriesResponse response) {
        return response.getValues() == null
                ? emptyList()
                : response.getValues().stream().map(BitbucketServiceImpl.this::convertRepository).collect(toList());
    }

    private Repository convertRepository(BitbucketRepository bbRepo) {
        Repository repo = new Repository();
        repo.setId(bbRepo.getUuid());
        repo.setFullName(bbRepo.getFullName());
        return repo;
    }
}

public class OAuth2JwtExampleClient {

    /**
     * Start client, then navigate to http://localhost:8080/auth/login.
     */
    public static void main(String[] args) throws Exception {
        AuthCallbackHandler authEndpoint = new AuthCallbackHandler(8081);
        authEndpoint.start(SOCKET_READ_TIMEOUT, true);

        HttpResponse response = getRepositories(null);
        assert (response.getStatusLine().getStatusCode() == SC_UNAUTHORIZED);

        Tokens tokens = authEndpoint.getTokens();
        System.out.println("Received tokens: " + tokens);
        response = getRepositories(tokens.getAccessToken());
        assert (response.getStatusLine().getStatusCode() == SC_OK);
        System.out.println("Repositories: " + IOUtils.toString(response.getEntity().getContent(), UTF_8));

        // emulate token usage - wait for some time until iat and exp attributes get updated
        // otherwise we will receive the same token
        Thread.sleep(5000);

        tokens = refreshToken(tokens.getRefreshToken());
        System.out.println("Refreshed tokens: " + tokens);

        // use refreshed token
        response = getRepositories(tokens.getAccessToken());
        assert (response.getStatusLine().getStatusCode() == SC_OK);
    }

    private static Tokens refreshToken(String refreshToken) throws IOException {
        BasicClientCookie cookie = new BasicClientCookie(REFRESH_TOKEN, refreshToken);
        cookie.setPath("/");
        cookie.setDomain("localhost");
        BasicCookieStore cookieStore = new BasicCookieStore();
        cookieStore.addCookie(cookie);

        HttpPost request = new HttpPost("http://localhost:8080/auth/token");
        request.setHeader(ACCEPT, APPLICATION_JSON.getMimeType());

        HttpClient httpClient = HttpClientBuilder.create().setDefaultCookieStore(cookieStore).build();
        HttpResponse execute = httpClient.execute(request);

        Gson gson = new Gson();
        Type type = new TypeToken<Map<String, String>>() {
        }.getType();
        Map<String, String> response = gson.fromJson(IOUtils.toString(execute.getEntity().getContent(), UTF_8), type);

        Cookie refreshTokenCookie = cookieStore.getCookies().stream()
                .filter(c -> REFRESH_TOKEN.equals(c.getName()))
                .findAny()
                .orElseThrow(() -> new IOException("Refresh token cookie not found."));
        return Tokens.of(response.get("token"), refreshTokenCookie.getValue());
    }

    private static HttpResponse getRepositories(String accessToken) throws IOException {
        HttpClient httpClient = HttpClientBuilder.create().build();
        HttpGet request = new HttpGet("http://localhost:8080/api/repositories");
        request.setHeader(ACCEPT, APPLICATION_JSON.getMimeType());
        if (accessToken != null) {
            request.setHeader(AUTHORIZATION, "Bearer " + accessToken);
        }
        return httpClient.execute(request);
    }
}