Add MockWebSession for use with MockServerWebExchange

Issue: SPR-16772

spring-test/src/main/java/org/springframework/mock/web/server/MockServerWebExchange.java

@@ -109,8 +109,10 @@ public final class MockServerWebExchange extends DefaultServerWebExchange {
 
 		/**
 		 * Set the session to use for the exchange.
-		 * <p>This is mutually exclusive with {@link #sessionManager(WebSessionManager)}.
+		 * <p>This method is mutually exclusive with
+		 * {@link #sessionManager(WebSessionManager)}.
 		 * @param session the session to use
+		 * @see MockWebSession
 		 */
 		public Builder session(WebSession session) {
 			this.sessionManager = exchange -> Mono.just(session);

spring-test/src/main/java/org/springframework/mock/web/server/MockWebSession.java

@@ -0,0 +1,119 @@
+/*
+ * Copyright 2002-2018 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.mock.web.server;
+
+import java.time.Clock;
+import java.time.Duration;
+import java.time.Instant;
+import java.util.Map;
+
+import reactor.core.publisher.Mono;
+
+import org.springframework.web.server.WebSession;
+import org.springframework.web.server.session.InMemoryWebSessionStore;
+
+/**
+ * Implementation of {@code WebSession} that delegates to a session instance
+ * obtained via {@link InMemoryWebSessionStore}.
+ *
+ * <p>This is intended for use with the
+ * {@link MockServerWebExchange.Builder#session(WebSession) session(WebSession)}
+ * method of the {@code MockServerWebExchange} builder, eliminating the need
+ * to use {@code WebSessionManager} or {@code WebSessionStore} altogether.
+ *
+ * @author Rossen Stoyanchev
+ * @since 5.1
+ */
+public class MockWebSession implements WebSession {
+
+	private final WebSession delegate;
+
+
+	public MockWebSession() {
+		this(null);
+	}
+
+	@SuppressWarnings("ConstantConditions")
+	public MockWebSession(Clock clock) {
+		InMemoryWebSessionStore sessionStore = new InMemoryWebSessionStore();
+		if (clock != null) {
+			sessionStore.setClock(clock);
+		}
+		this.delegate = sessionStore.createWebSession().block();
+	}
+
+
+	@Override
+	public String getId() {
+		return this.delegate.getId();
+	}
+
+	@Override
+	public Map<String, Object> getAttributes() {
+		return this.delegate.getAttributes();
+	}
+
+	@Override
+	public void start() {
+		this.delegate.start();
+	}
+
+	@Override
+	public boolean isStarted() {
+		return this.delegate.isStarted();
+	}
+
+	@Override
+	public Mono<Void> changeSessionId() {
+		return this.delegate.changeSessionId();
+	}
+
+	@Override
+	public Mono<Void> invalidate() {
+		return this.delegate.invalidate();
+	}
+
+	@Override
+	public Mono<Void> save() {
+		return this.delegate.save();
+	}
+
+	@Override
+	public boolean isExpired() {
+		return this.delegate.isExpired();
+	}
+
+	@Override
+	public Instant getCreationTime() {
+		return this.delegate.getCreationTime();
+	}
+
+	@Override
+	public Instant getLastAccessTime() {
+		return this.delegate.getLastAccessTime();
+	}
+
+	@Override
+	public void setMaxIdleTime(Duration maxIdleTime) {
+		this.delegate.setMaxIdleTime(maxIdleTime);
+	}
+
+	@Override
+	public Duration getMaxIdleTime() {
+		return this.delegate.getMaxIdleTime();
+	}
+
+}