Switch RequestContextListener to Filter

Update WebMvcAutoConfiguration to use a RequestContextFilter instead of
a RequestContextListener.

Using a filter is required for some Spring Session operations (see
https://github.com/spring-projects/spring-session/issues/129).

This update also has the added benefit of allowing the Response to be
accessed from RequestContextHolder.getRequestAttributes() by casting it
to ServletRequestAttributes.

Fixes gh-2637

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/web/WebMvcAutoConfiguration.java

@@ -42,6 +42,7 @@ import org.springframework.boot.autoconfigure.web.ResourceProperties.Strategy;
 import org.springframework.boot.context.properties.EnableConfigurationProperties;
 import org.springframework.boot.context.web.OrderedHiddenHttpMethodFilter;
 import org.springframework.boot.context.web.OrderedHttpPutFormContentFilter;
+import org.springframework.boot.context.web.OrderedRequestContextFilter;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.context.annotation.Import;
@@ -61,6 +62,7 @@ import org.springframework.web.bind.support.ConfigurableWebBindingInitializer;
 import org.springframework.web.context.request.RequestContextListener;
 import org.springframework.web.filter.HiddenHttpMethodFilter;
 import org.springframework.web.filter.HttpPutFormContentFilter;
+import org.springframework.web.filter.RequestContextFilter;
 import org.springframework.web.servlet.DispatcherServlet;
 import org.springframework.web.servlet.LocaleResolver;
 import org.springframework.web.servlet.View;
@@ -163,9 +165,10 @@ public class WebMvcAutoConfiguration {
 		}
 
 		@Bean
-		@ConditionalOnMissingBean
-		public RequestContextListener requestContextListener() {
-			return new RequestContextListener();
+		@ConditionalOnMissingBean({ RequestContextListener.class,
+				RequestContextFilter.class })
+		public RequestContextFilter requestContextFilter() {
+			return new OrderedRequestContextFilter();
 		}
 
 		@Bean

spring-boot/src/main/java/org/springframework/boot/context/web/OrderedRequestContextFilter.java

@@ -0,0 +1,46 @@
+/*
+ * Copyright 2012-2015 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.boot.context.web;
+
+import org.springframework.core.Ordered;
+import org.springframework.web.filter.RequestContextFilter;
+
+/**
+ * {@link RequestContextFilter} that also implements {@link Ordered}.
+ *
+ * @author Phillip Webb
+ * @since 1.3.0
+ */
+public class OrderedRequestContextFilter extends RequestContextFilter implements Ordered {
+
+	// Order defaults to high but after Spring Session filter
+	private int order = Ordered.HIGHEST_PRECEDENCE + 100;
+
+	@Override
+	public int getOrder() {
+		return this.order;
+	}
+
+	/**
+	 * Set the order for this filter.
+	 * @param order the order to set
+	 */
+	public void setOrder(int order) {
+		this.order = order;
+	}
+
+}