7. WebSession Integration

We have already mentioned that Spring Session provides transparent integration with Spring WebFlux’s WebSession, but what benefits do we get out of this? As with HttpSession, Spring Session makes it trivial to support clustered sessions without being tied to an application container specific solution.

Using Spring Session with WebSession is enabled by registering a WebSessionManager implementation backed by Spring Session’s ReactiveSessionRepository. The Spring configuration is responsible for creating a WebSessionManager that replaces the WebSession implementation with an implementation backed by Spring Session. To do so, add the following Spring Configuration:

@EnableRedisWebSession 
public class SessionConfiguration {

	@Bean
	public LettuceConnectionFactory redisConnectionFactory() {
		return new LettuceConnectionFactory(); 
	}

}

It is considerably easier for Spring Session to integrate with Spring WebFlux and its WebSession, compared to Servlet API and its HttpSession. Spring WebFlux provides the WebSessionStore API, which presents a strategy for persisting WebSession.

	Note
	This section describes how Spring Session provides transparent integration with WebSession. We offer this content so that you can understand what is happening under the covers. This functionality is already integrated and you do NOT need to implement this logic yourself.

First, we create a custom SpringSessionWebSession that delegates to Spring Session’s Session. It looks something like the following:

public class SpringSessionWebSession implements WebSession {

	enum State {
		NEW, STARTED
	}

	private final S session;

	private AtomicReference<State> state = new AtomicReference<>();

	SpringSessionWebSession(S session, State state) {
		this.session = session;
		this.state.set(state);
	}

	@Override
	public void start() {
		this.state.compareAndSet(State.NEW, State.STARTED);
	}

	@Override
	public boolean isStarted() {
		State value = this.state.get();
		return (State.STARTED.equals(value)
				|| (State.NEW.equals(value) && !this.session.getAttributes().isEmpty()));
	}

	@Override
	public Mono<Void> changeSessionId() {
		return Mono.defer(() -> {
			this.session.changeSessionId();
			return save();
		});
	}

	// ... other methods delegate to the original Session
}

Next, we create a custom WebSessionStore that delegates to the ReactiveSessionRepository and wraps Session into custom WebSession implementation, as the following listing shows:

public class SpringSessionWebSessionStore<S extends Session> implements WebSessionStore {

	private final ReactiveSessionRepository<S> sessions;

	public SpringSessionWebSessionStore(ReactiveSessionRepository<S> reactiveSessionRepository) {
		this.sessions = reactiveSessionRepository;
	}

	// ...
}

To be detected by Spring WebFlux, this custom WebSessionStore needs to be registered with ApplicationContext as a bean named webSessionManager. For additional information on Spring WebFlux, see the Spring Framework Reference Documentation.