WebSession Integration

Spring Session provides transparent integration with Spring WebFlux’s WebSession. This means that you can switch the WebSession implementation out with an implementation that is backed by Spring Session.

Why Spring Session and WebSession?

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.

WebSession with Redis

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 (1)
public class SessionConfiguration {

	@Bean
	public LettuceConnectionFactory redisConnectionFactory() {
		return new LettuceConnectionFactory(); (2)
	}

}

1	The `@EnableRedisWebSession` annotation creates a Spring bean with the name of `webSessionManager`. That bean implements the `WebSessionManager`. This is what is in charge of replacing the `WebSession` implementation to be backed by Spring Session. In this instance, Spring Session is backed by Redis.
2	We create a `RedisConnectionFactory` that connects Spring Session to the Redis Server. We configure the connection to connect to localhost on the default port (6379) For more information on configuring Spring Data Redis, see the reference documentation.

How WebSession Integration Works

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.

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.