Add filter to force WebSession::save.

docs/src/main/asciidoc/spring-cloud-gateway.adoc

@@ -509,6 +509,27 @@ spring:
 
 For a request path of `/foo/bar`, this will set the path to `/bar` before making the downstream request. Notice the `$\` which is replaced with `$` because of the YAML spec.
 
+=== SaveSession GatewayFilter Factory
+The SaveSession GatewayFilter Factory forces a `WebSession::save` operation _before_ forwarding the call downstream. This is of particular use when
+using something like http://projects.spring.io/spring-session/[Spring Session] with a lazy data store and need to ensure the session state has been saved before making the forwarded call.
+
+.application.yml
+[source,yaml]
+----
+spring:
+  cloud:
+    gateway:
+      routes:
+      - id: save_session
+        uri: http://example.org
+        predicates:
+        - Path=/foo/**
+        filters:
+        - SaveSession
+----
+
+If you are integrating http://projects.spring.io/spring-security/[Spring Security] with Spring Session, and want to ensure security details have been forwarded to the remote process, this is critical.
+
 === SecureHeaders GatewayFilter Factory
 The SecureHeaders GatewayFilter Factory adds a number of headers to the response at the reccomendation from https://blog.appcanary.com/2017/http-security-headers.html[this blog post].
 

spring-cloud-gateway-core/src/main/java/org/springframework/cloud/gateway/config/GatewayAutoConfiguration.java

@@ -54,6 +54,7 @@
 import org.springframework.cloud.gateway.filter.factory.RemoveResponseHeaderGatewayFilterFactory;
 import org.springframework.cloud.gateway.filter.factory.RequestRateLimiterGatewayFilterFactory;
 import org.springframework.cloud.gateway.filter.factory.RewritePathGatewayFilterFactory;
+import org.springframework.cloud.gateway.filter.factory.SaveSessionGatewayFilterFactory;
 import org.springframework.cloud.gateway.filter.factory.SecureHeadersGatewayFilterFactory;
 import org.springframework.cloud.gateway.filter.factory.SecureHeadersProperties;
 import org.springframework.cloud.gateway.filter.factory.SetPathGatewayFilterFactory;
@@ -101,7 +102,6 @@
 import reactor.core.publisher.Flux;
 import reactor.ipc.netty.http.client.HttpClient;
 import reactor.ipc.netty.http.client.HttpClientOptions;
-import reactor.ipc.netty.http.client.HttpClientRequest;
 import reactor.ipc.netty.resources.PoolResources;
 import rx.RxReactiveStreams;
 
@@ -404,6 +404,10 @@ public SetStatusGatewayFilterFactory setStatusGatewayFilterFactory() {
 		return new SetStatusGatewayFilterFactory();
 	}
 
+	@Bean
+	public SaveSessionGatewayFilterFactory saveSessionGatewayFilterFactory() {
+		return new SaveSessionGatewayFilterFactory();
+	}
 
 	@ManagementContextConfiguration
 	@ConditionalOnProperty(value = "management.gateway.enabled", matchIfMissing = true)

spring-cloud-gateway-core/src/main/java/org/springframework/cloud/gateway/filter/factory/SaveSessionGatewayFilterFactory.java

@@ -0,0 +1,38 @@
+/*
+ * Copyright 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.cloud.gateway.filter.factory;
+
+import org.springframework.cloud.gateway.filter.GatewayFilter;
+import org.springframework.tuple.Tuple;
+import org.springframework.web.server.WebSession;
+
+/**
+ * Save the current {@link WebSession} before executing the rest of the {@link org.springframework.cloud.gateway.filter.GatewayFilterChain}.
+ *
+ * Filter is very useful for situation where the WebSession is lazy (e.g. Spring Session MongoDB) and making a remote call requires
+ * that {@link WebSession#save()} be called before the remote call is made.
+ * 
+ * @author Greg Turnquist
+ */
+public class SaveSessionGatewayFilterFactory implements GatewayFilterFactory {
+
+	@Override
+	public GatewayFilter apply(Tuple args) {
+		return (exchange, chain) -> exchange.getSession()
+			.map(WebSession::save)
+			.then(chain.filter(exchange));
+	}
+}

spring-cloud-gateway-core/src/main/java/org/springframework/cloud/gateway/route/builder/GatewayFilterSpec.java

@@ -37,6 +37,7 @@
 import org.springframework.cloud.gateway.filter.factory.RemoveResponseHeaderGatewayFilterFactory;
 import org.springframework.cloud.gateway.filter.factory.RequestRateLimiterGatewayFilterFactory;
 import org.springframework.cloud.gateway.filter.factory.RewritePathGatewayFilterFactory;
+import org.springframework.cloud.gateway.filter.factory.SaveSessionGatewayFilterFactory;
 import org.springframework.cloud.gateway.filter.factory.SecureHeadersGatewayFilterFactory;
 import org.springframework.cloud.gateway.filter.factory.SetPathGatewayFilterFactory;
 import org.springframework.cloud.gateway.filter.factory.SetRequestHeaderGatewayFilterFactory;
@@ -197,4 +198,8 @@ public GatewayFilterSpec setStatus(String status) {
 	public GatewayFilterSpec setStatus(HttpStatus status) {
 		return filter(getBean(SetStatusGatewayFilterFactory.class).apply(status));
 	}
+
+	public GatewayFilterSpec saveSession() {
+		return filter(getBean(SaveSessionGatewayFilterFactory.class).apply(EMPTY_TUPLE));
+	}
 }

spring-cloud-gateway-core/src/test/java/org/springframework/cloud/gateway/filter/factory/SaveSessionGatewayFilterFactoryTests.java

@@ -0,0 +1,85 @@
+/*
+ * Copyright 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.cloud.gateway.filter.factory;
+
+import java.time.Duration;
+import java.util.HashMap;
+import java.util.Map;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.springframework.boot.SpringBootConfiguration;
+import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.cloud.gateway.test.BaseWebClientTests;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Import;
+import org.springframework.test.annotation.DirtiesContext;
+import org.springframework.test.context.ActiveProfiles;
+import org.springframework.test.context.junit4.SpringRunner;
+import org.springframework.web.server.WebSession;
+import org.springframework.web.server.session.WebSessionManager;
+import reactor.core.publisher.Mono;
+import reactor.test.StepVerifier;
+
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
+import static org.springframework.boot.test.context.SpringBootTest.WebEnvironment.RANDOM_PORT;
+import static org.springframework.web.reactive.function.BodyExtractors.toMono;
+
+/**
+ * @author Greg Turnquist
+ */
+@RunWith(SpringRunner.class)
+@SpringBootTest(webEnvironment = RANDOM_PORT)
+@DirtiesContext
+@ActiveProfiles(profiles = "save-session-web-filter")
+public class SaveSessionGatewayFilterFactoryTests extends BaseWebClientTests {
+
+	static WebSession mockWebSession = mock(WebSession.class);
+
+	@Test
+	public void webCallShouldTriggerWebSessionSaveAction() {
+
+		when(mockWebSession.getAttributes()).thenReturn(new HashMap<>());
+		when(mockWebSession.save()).thenReturn(Mono.empty());
+
+		Mono<Map> result = webClient.get()
+			.uri("/get")
+			.exchange()
+			.flatMap(response -> response.body(toMono(Map.class)));
+
+		StepVerifier.create(result)
+			.consumeNextWith(response -> {/* Don't care about data, just need to catch signal */})
+			.expectComplete()
+			.verify(Duration.ofMinutes(10));
+
+		verify(mockWebSession).save();
+	}
+
+	@EnableAutoConfiguration
+	@SpringBootConfiguration
+	@Import(DefaultTestConfig.class)
+	static class TestConfig {
+
+		@Bean
+		WebSessionManager webSessionManager() {
+			return exchange -> Mono.just(mockWebSession);
+		}
+	}
+
+}

spring-cloud-gateway-core/src/test/resources/application-save-session-web-filter.yml

@@ -0,0 +1,14 @@
+test:
+  hostport: httpbin.org:80
+  uri: lb://testservice
+
+spring:
+  cloud:
+    gateway:
+      routes:
+      - id: save_session_test
+        uri: ${test.uri}
+        predicates:
+        - Path=/get
+        filters:
+        - SaveSession