Add WebSession.invalidate()

Issue: SPR-15960

spring-web/src/main/java/org/springframework/web/server/WebSession.java

@@ -109,6 +109,12 @@ public interface WebSession {
 	 */
 	Mono<Void> changeSessionId();
 
+	/**
+	 * Invalidate the current session and clear session storage.
+	 * @return completion notification (success or error)
+	 */
+	Mono<Void> invalidate();
+
 	/**
 	 * Save the session persisting attributes (e.g. if stored remotely) and also
 	 * sending the session id to the client if the session is new.

spring-web/src/main/java/org/springframework/web/server/session/DefaultWebSessionManager.java

@@ -90,26 +90,21 @@ public class DefaultWebSessionManager implements WebSessionManager {
 	}
 
 	private Mono<Void> save(ServerWebExchange exchange, WebSession session) {
-		if (session.isExpired()) {
-			return Mono.error(new IllegalStateException("Session='" + session.getId() + "' expired."));
-		}
 
-		if (!session.isStarted()) {
-			if (hasNewSessionId(exchange, session)) {
+		List<String> ids = getSessionIdResolver().resolveSessionIds(exchange);
+
+		if (!session.isStarted() || session.isExpired()) {
+			if (!ids.isEmpty()) {
+				// Expired on retrieve or while processing request, or invalidated..
 				this.sessionIdResolver.expireSession(exchange);
 			}
 			return Mono.empty();
 		}
 
-		if (hasNewSessionId(exchange, session)) {
+		if (ids.isEmpty() || !session.getId().equals(ids.get(0))) {
 			this.sessionIdResolver.setSessionId(exchange, session.getId());
 		}
 
 		return session.save();
 	}
-
-	private boolean hasNewSessionId(ServerWebExchange exchange, WebSession session) {
-		List<String> ids = getSessionIdResolver().resolveSessionIds(exchange);
-		return ids.isEmpty() || !session.getId().equals(ids.get(0));
-	}
 }

spring-web/src/main/java/org/springframework/web/server/session/InMemoryWebSessionStore.java

@@ -109,25 +109,22 @@ public class InMemoryWebSessionStore implements WebSessionStore {
 
 	private class InMemoryWebSession implements WebSession {
 
-		private final AtomicReference<String> id;
+		private final AtomicReference<String> id = new AtomicReference<>(String.valueOf(idGenerator.generateId()));
 
-		private final Map<String, Object> attributes;
+		private final Map<String, Object> attributes = new ConcurrentHashMap<>();
 
 		private final Instant creationTime;
 
 		private volatile Instant lastAccessTime;
 
-		private volatile Duration maxIdleTime;
+		private volatile Duration maxIdleTime = Duration.ofMinutes(30);
 
-		private volatile boolean started;
+		private final AtomicReference<State> state = new AtomicReference<>(State.NEW);
 
 
 		InMemoryWebSession() {
-			this.id = new AtomicReference<>(String.valueOf(idGenerator.generateId()));
-			this.attributes = new ConcurrentHashMap<>();
 			this.creationTime = Instant.now(getClock());
 			this.lastAccessTime = this.creationTime;
-			this.maxIdleTime = Duration.ofMinutes(30);
 		}
 
 
@@ -163,12 +160,12 @@ public class InMemoryWebSessionStore implements WebSessionStore {
 
 		@Override
 		public void start() {
-			this.started = true;
+			this.state.compareAndSet(State.NEW, State.STARTED);
 		}
 
 		@Override
 		public boolean isStarted() {
-			return this.started || !getAttributes().isEmpty();
+			return this.state.get().equals(State.STARTED) || !getAttributes().isEmpty();
 		}
 
 		@Override
@@ -185,21 +182,46 @@ public class InMemoryWebSessionStore implements WebSessionStore {
 			return Mono.empty();
 		}
 
+		@Override
+		public Mono<Void> invalidate() {
+			this.state.set(State.EXPIRED);
+			getAttributes().clear();
+			InMemoryWebSessionStore.this.sessions.remove(this.id.get());
+			return Mono.empty();
+		}
+
 		@Override
 		public Mono<Void> save() {
+			if (!getAttributes().isEmpty()) {
+				this.state.compareAndSet(State.NEW, State.STARTED);
+			}
 			InMemoryWebSessionStore.this.sessions.put(this.getId(), this);
 			return Mono.empty();
 		}
 
 		@Override
 		public boolean isExpired() {
-			return (isStarted() && !this.maxIdleTime.isNegative() &&
-					Instant.now(getClock()).minus(this.maxIdleTime).isAfter(this.lastAccessTime));
+			if (this.state.get().equals(State.EXPIRED)) {
+				return true;
+			}
+			if (checkExpired()) {
+				this.state.set(State.EXPIRED);
+				return true;
+			}
+			return false;
+		}
+
+		private boolean checkExpired() {
+			return isStarted() && !this.maxIdleTime.isNegative() &&
+					Instant.now(getClock()).minus(this.maxIdleTime).isAfter(this.lastAccessTime);
 		}
 
 		private void updateLastAccessTime() {
 			this.lastAccessTime = Instant.now(getClock());
 		}
+
 	}
 
+	private enum State { NEW, STARTED, EXPIRED }
+
 }