Add an integration test to verify filter ordering

We have some requirements for filter ordering:

1. The character encoding filter must go first
2. Spring Session’s filter should go early
3. RequestContextFilter should go late so that it any request wrapping
   performed by other filters is reflected in the request that’s set
   in the RequestContextHolder
4. Spring Security’s Filter must go after RequestContextFilter so that
   any code called by Filters in Spring Security’s Filter chain can
   retrieve the request from RequestContextHolder, for example
   OAuth2ClientContextFilter.

See gh-4331

spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/web/FilterOrderingIntegrationTests.java

@@ -0,0 +1,121 @@
+/*
+ * 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.autoconfigure.web;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import javax.servlet.Filter;
+
+import org.junit.After;
+import org.junit.Test;
+
+import org.springframework.boot.autoconfigure.PropertyPlaceholderAutoConfiguration;
+import org.springframework.boot.autoconfigure.security.SecurityAutoConfiguration;
+import org.springframework.boot.autoconfigure.session.SessionAutoConfiguration;
+import org.springframework.boot.context.embedded.AnnotationConfigEmbeddedWebApplicationContext;
+import org.springframework.boot.context.embedded.EmbeddedServletContainerCustomizerBeanPostProcessor;
+import org.springframework.boot.context.embedded.MockEmbeddedServletContainerFactory;
+import org.springframework.boot.context.embedded.MockEmbeddedServletContainerFactory.RegisteredFilter;
+import org.springframework.boot.context.web.OrderedCharacterEncodingFilter;
+import org.springframework.boot.context.web.OrderedRequestContextFilter;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.data.redis.connection.RedisConnection;
+import org.springframework.data.redis.connection.RedisConnectionFactory;
+import org.springframework.security.web.FilterChainProxy;
+import org.springframework.session.web.http.SessionRepositoryFilter;
+
+import static org.hamcrest.Matchers.contains;
+import static org.hamcrest.Matchers.instanceOf;
+import static org.junit.Assert.assertThat;
+import static org.mockito.BDDMockito.given;
+import static org.mockito.Mockito.mock;
+
+/**
+ * Integration tests that verify the ordering of various filters that are auto-configured.
+ *
+ * @author Andy Wilkinson
+ */
+public class FilterOrderingIntegrationTests {
+
+	private AnnotationConfigEmbeddedWebApplicationContext context;
+
+	@After
+	public void cleanup() {
+		if (this.context != null) {
+			this.context.close();
+		}
+	}
+
+	@Test
+	@SuppressWarnings("unchecked")
+	public void testFilterOrdering() {
+		load();
+		List<RegisteredFilter> registeredFilters = this.context
+				.getBean(MockEmbeddedServletContainerFactory.class).getContainer()
+				.getRegisteredFilters();
+		List<Filter> filters = new ArrayList<Filter>(registeredFilters.size());
+		for (RegisteredFilter registeredFilter : registeredFilters) {
+			filters.add(registeredFilter.getFilter());
+		}
+		assertThat(filters, contains(instanceOf(OrderedCharacterEncodingFilter.class),
+				instanceOf(SessionRepositoryFilter.class), instanceOf(Filter.class),
+				instanceOf(Filter.class), instanceOf(OrderedRequestContextFilter.class),
+				instanceOf(FilterChainProxy.class)));
+	}
+
+	private void load() {
+		this.context = new AnnotationConfigEmbeddedWebApplicationContext();
+		this.context.register(MockEmbeddedServletContainerConfiguration.class,
+				TestRedisConfiguration.class, WebMvcAutoConfiguration.class,
+				SecurityAutoConfiguration.class, SessionAutoConfiguration.class,
+				HttpMessageConvertersAutoConfiguration.class,
+				PropertyPlaceholderAutoConfiguration.class,
+				HttpEncodingAutoConfiguration.class);
+		this.context.refresh();
+	}
+
+	@Configuration
+	static class MockEmbeddedServletContainerConfiguration {
+
+		@Bean
+		public MockEmbeddedServletContainerFactory containerFactory() {
+			return new MockEmbeddedServletContainerFactory();
+		}
+
+		@Bean
+		public EmbeddedServletContainerCustomizerBeanPostProcessor embeddedServletContainerCustomizerBeanPostProcessor() {
+			return new EmbeddedServletContainerCustomizerBeanPostProcessor();
+		}
+
+	}
+
+	@Configuration
+	static class TestRedisConfiguration {
+
+		@Bean
+		public RedisConnectionFactory redisConnectionFactory() {
+			RedisConnectionFactory connectionFactory = mock(RedisConnectionFactory.class);
+			RedisConnection connection = mock(RedisConnection.class);
+			given(connectionFactory.getConnection()).willReturn(connection);
+			return connectionFactory;
+		}
+
+	}
+
+}