Principal is null for every Spring websocket event

Question

I'm trying to get the the Principal user name from Spring websocket SessionConnectEvent but it is null on every listener. What I can be doing wrong?

To implement it I followed the answers you will find here: how to capture connection event in my webSocket server with Spring 4?

@Slf4j
@Service
public class SessionEventListener {

    @EventListener
    private void handleSessionConnect(SessionConnectEvent event) {
        SimpMessageHeaderAccessor headers = SimpMessageHeaderAccessor.wrap(event.getMessage());
        String sessionId = headers.getSessionId();
        log.debug("sessionId is " + sessionId);
        String username = headers.getUser().getName(); // headers.getUser() is null
        log.debug("username is " + username);
    }

    @EventListener
    private void handleSessionConnected(SessionConnectEvent event) {
        SimpMessageHeaderAccessor headers = SimpMessageHeaderAccessor.wrap(event.getMessage());
        String sessionId = headers.getSessionId();
        log.debug("sessionId is " + sessionId);
        String username = headers.getUser().getName(); // headers.getUser() is null
        log.debug("username is " + username);
    }

    @EventListener
    private void handleSubscribeEvent(SessionSubscribeEvent event) {
        SimpMessageHeaderAccessor headers = SimpMessageHeaderAccessor.wrap(event.getMessage());
        String sessionId = headers.getSessionId();
        log.debug("sessionId is " + sessionId);
        String subscriptionId = headers.getSubscriptionId();
        log.debug("subscriptionId is " + subscriptionId);
        String username = headers.getUser().getName(); // headers.getUser() is null
        log.debug("username is " + username);
    }

    @EventListener
    private void handleUnsubscribeEvent(SessionUnsubscribeEvent event) {
        SimpMessageHeaderAccessor headers = SimpMessageHeaderAccessor.wrap(event.getMessage());
        String sessionId = headers.getSessionId();
        log.debug("sessionId is " + sessionId);
        String subscriptionId = headers.getSubscriptionId();
        log.debug("subscriptionId is " + subscriptionId);
        String username = headers.getUser().getName(); // headers.getUser() is null
        log.debug("username is " + username);
    }

    @EventListener
    private void handleSessionDisconnect(SessionDisconnectEvent event) {
        SimpMessageHeaderAccessor headers = SimpMessageHeaderAccessor.wrap(event.getMessage());
        log.debug("sessionId is " + event.getSessionId());
        String username = headers.getUser().getName(); // headers.getUser() is null
        log.debug("username is " + username);
    }

}

This is my security config:

@Configuration
@EnableWebSecurity
public class SecurityConfig extends WebSecurityConfigurerAdapter {

    @Override
    protected void configure(HttpSecurity http) throws Exception {
        http.authorizeRequests()
            .anyRequest()
            .permitAll()
            .and().csrf().disable();
    }
}

Answer 1

As I'm not implementing an authentication mechanisim, Spring has no enough information to provide a Principal user name. So what I had to do is to configure a HandshakeHandler that generates the Principal.

@Configuration
@EnableWebSocketMessageBroker
public class WebSocketConfig implements WebSocketMessageBrokerConfigurer {

    public static final String ENDPOINT_CONNECT = "/connect";
    public static final String SUBSCRIBE_USER_PREFIX = "/private";
    public static final String SUBSCRIBE_USER_REPLY = "/reply";
    public static final String SUBSCRIBE_QUEUE = "/queue";

    @Override
    public void configureMessageBroker(MessageBrokerRegistry registry) {
        registry.enableSimpleBroker(SUBSCRIBE_QUEUE, SUBSCRIBE_USER_REPLY);
        registry.setUserDestinationPrefix(SUBSCRIBE_USER_PREFIX);
    }

    @Override
    public void registerStompEndpoints(StompEndpointRegistry registry) {
        registry.addEndpoint(ENDPOINT_CONNECT)
                // assign a random username as principal for each websocket client
                // this is needed to be able to communicate with a specific client
                .setHandshakeHandler(new AssignPrincipalHandshakeHandler())
                .setAllowedOrigins("*");
    }

}

/**
 * Assign a random username as principal for each websocket client. This is
 * needed to be able to communicate with a specific client.
 */
public class AssignPrincipalHandshakeHandler extends DefaultHandshakeHandler {
    private static final String ATTR_PRINCIPAL = "__principal__";

    @Override
    protected Principal determineUser(ServerHttpRequest request, WebSocketHandler wsHandler, Map<String, Object> attributes) {
        final String name;
        if (!attributes.containsKey(ATTR_PRINCIPAL)) {
            name = generateRandomUsername();
            attributes.put(ATTR_PRINCIPAL, name);
        } else {
            name = (String) attributes.get(ATTR_PRINCIPAL);
        }
        return new Principal() {
            @Override
            public String getName() {
                return name;
            }
        };
    }

    private String generateRandomUsername() {
        RandomStringGenerator randomStringGenerator = 
                new RandomStringGenerator.Builder()
                    .withinRange('0', 'z')
                    .filteredBy(CharacterPredicates.LETTERS, CharacterPredicates.DIGITS).build();
        return randomStringGenerator.generate(32);
    }
}