WebSocket Integration
Spring Session provides transparent integration with Spring’s WebSocket support.
Spring Session’s WebSocket support works only with Spring’s WebSocket support. Specifically,it does not work with using JSR-356 directly, because JSR-356 does not have a mechanism for intercepting incoming WebSocket messages. |
Why Spring Session and WebSockets?
So why do we need Spring Session when we use WebSockets?
Consider an email application that does much of its work through HTTP requests.
However, there is also a chat application embedded within it that works over WebSocket APIs.
If a user is actively chatting with someone, we should not timeout the HttpSession
, since this would be a pretty poor user experience.
However, this is exactly what JSR-356 does.
Another issue is that, according to JSR-356, if the HttpSession
times out, any WebSocket that was created with that HttpSession
and an authenticated user should be forcibly closed.
This means that, if we are actively chatting in our application and are not using the HttpSession, we also do disconnect from our conversation.
WebSocket Usage
The WebSocket Sample provides a working sample of how to integrate Spring Session with WebSockets. You can follow the basic steps for integration described in the next few headings, but we encourage you to follow along with the detailed WebSocket Guide when integrating with your own application.
HttpSession
Integration
Before using WebSocket integration, you should be sure that you have HttpSession
Integration working first.
Spring Configuration
In a typical Spring WebSocket application, you would implement WebSocketMessageBrokerConfigurer
.
For example, the configuration might look something like the following:
@Configuration
@EnableScheduling
@EnableWebSocketMessageBroker
public class WebSocketConfig implements WebSocketMessageBrokerConfigurer {
@Override
public void registerStompEndpoints(StompEndpointRegistry registry) {
registry.addEndpoint("/messages").withSockJS();
}
@Override
public void configureMessageBroker(MessageBrokerRegistry registry) {
registry.enableSimpleBroker("/queue/", "/topic/");
registry.setApplicationDestinationPrefixes("/app");
}
}
We can update our configuration to use Spring Session’s WebSocket support. The following example shows how to do so:
@Configuration
@EnableScheduling
@EnableWebSocketMessageBroker
public class WebSocketConfig extends AbstractSessionWebSocketMessageBrokerConfigurer<Session> { (1)
@Override
protected void configureStompEndpoints(StompEndpointRegistry registry) { (2)
registry.addEndpoint("/messages").withSockJS();
}
@Override
public void configureMessageBroker(MessageBrokerRegistry registry) {
registry.enableSimpleBroker("/queue/", "/topic/");
registry.setApplicationDestinationPrefixes("/app");
}
}
To hook in the Spring Session support we only need to change two things:
1 | Instead of implementing WebSocketMessageBrokerConfigurer , we extend AbstractSessionWebSocketMessageBrokerConfigurer |
2 | We rename the registerStompEndpoints method to configureStompEndpoints |
What does AbstractSessionWebSocketMessageBrokerConfigurer
do behind the scenes?
-
WebSocketConnectHandlerDecoratorFactory
is added as aWebSocketHandlerDecoratorFactory
toWebSocketTransportRegistration
. This ensures a customSessionConnectEvent
is fired that contains theWebSocketSession
. TheWebSocketSession
is necessary to end any WebSocket connections that are still open when a Spring Session is ended. -
SessionRepositoryMessageInterceptor
is added as aHandshakeInterceptor
to everyStompWebSocketEndpointRegistration
. This ensures that theSession
is added to the WebSocket properties to enable updating the last accessed time. -
SessionRepositoryMessageInterceptor
is added as aChannelInterceptor
to our inboundChannelRegistration
. This ensures that every time an inbound message is received, that the last accessed time of our Spring Session is updated. -
WebSocketRegistryListener
is created as a Spring bean. This ensures that we have a mapping of all of theSession
IDs to the corresponding WebSocket connections. By maintaining this mapping, we can close all the WebSocket connections when a Spring Session (HttpSession) is ended.