Add WebMvcRegistrations for custom MVC components

Add `WebMvcRegistrations` which can be used to provide custom
instances of `RequestMappingHandlerMapping`,
`RequestMappingHandlerAdapter` and `ExceptionHandlerExceptionResolver`.
Those instances are then used and processed by the Boot MVC
configuration.

Prior to this commit, developers could provide their custom instances
of MVC infrstructure components such as `RequestMappingHandlerMapping`
and `RequestMappingHandlerAdapter` only by using advanced configuration
strategies. Those advanced configurations involved subclassing
`WebMvcConfigurationSupport` which effectively turns off MVC
auto-configuration in Boot.

Fixes gh-5004
Closes gh-6100

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

@@ -83,6 +83,7 @@ import org.springframework.web.servlet.config.annotation.WebMvcConfigurationSupp
 import org.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter;
 import org.springframework.web.servlet.handler.SimpleUrlHandlerMapping;
 import org.springframework.web.servlet.i18n.FixedLocaleResolver;
+import org.springframework.web.servlet.mvc.method.annotation.ExceptionHandlerExceptionResolver;
 import org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter;
 import org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping;
 import org.springframework.web.servlet.resource.AppCacheManifestTransformer;
@@ -342,10 +343,14 @@ public class WebMvcAutoConfiguration {
 
 		private final ListableBeanFactory beanFactory;
 
+		private final WebMvcRegistrations mvcRegistrations;
+
 		public EnableWebMvcConfiguration(
 				ObjectProvider<WebMvcProperties> mvcPropertiesProvider,
+				ObjectProvider<WebMvcRegistrations> mvcRegistrationsProvider,
 				ListableBeanFactory beanFactory) {
 			this.mvcProperties = mvcPropertiesProvider.getIfAvailable();
+			this.mvcRegistrations = mvcRegistrationsProvider.getIfUnique();
 			this.beanFactory = beanFactory;
 		}
 
@@ -358,6 +363,15 @@ public class WebMvcAutoConfiguration {
 			return adapter;
 		}
 
+		@Override
+		protected RequestMappingHandlerAdapter createRequestMappingHandlerAdapter() {
+			if (this.mvcRegistrations != null
+					&& this.mvcRegistrations.getRequestMappingHandlerAdapter() != null) {
+				return this.mvcRegistrations.getRequestMappingHandlerAdapter();
+			}
+			return super.createRequestMappingHandlerAdapter();
+		}
+
 		@Bean
 		@Primary
 		@Override
@@ -366,6 +380,15 @@ public class WebMvcAutoConfiguration {
 			return super.requestMappingHandlerMapping();
 		}
 
+		@Override
+		protected RequestMappingHandlerMapping createRequestMappingHandlerMapping() {
+			if (this.mvcRegistrations != null
+					&& this.mvcRegistrations.getRequestMappingHandlerMapping() != null) {
+				return this.mvcRegistrations.getRequestMappingHandlerMapping();
+			}
+			return super.createRequestMappingHandlerMapping();
+		}
+
 		@Override
 		protected ConfigurableWebBindingInitializer getConfigurableWebBindingInitializer() {
 			try {
@@ -376,6 +399,14 @@ public class WebMvcAutoConfiguration {
 			}
 		}
 
+		@Override
+		protected ExceptionHandlerExceptionResolver createExceptionHandlerExceptionResolver() {
+			if (this.mvcRegistrations != null && this.mvcRegistrations
+					.getExceptionHandlerExceptionResolver() != null) {
+				return this.mvcRegistrations.getExceptionHandlerExceptionResolver();
+			}
+			return super.createExceptionHandlerExceptionResolver();
+		}
 	}
 
 	@Configuration

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

@@ -0,0 +1,59 @@
+/*
+ * Copyright 2012-2016 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 org.springframework.web.servlet.config.annotation.WebMvcConfigurationSupport;
+import org.springframework.web.servlet.mvc.method.annotation.ExceptionHandlerExceptionResolver;
+import org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter;
+import org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping;
+
+/**
+ * Interface to register key components of the {@link WebMvcConfigurationSupport} in place
+ * of the default ones provided by Spring MVC.
+ * <p>
+ * All custom instances are later processed by Boot and Spring MVC configurations. A
+ * single instance of this component should be registered, otherwise making it impossible
+ * to choose from redundant MVC components.
+ *
+ * @author Brian Clozel
+ * @since 1.4.0
+ * @see org.springframework.boot.autoconfigure.web.WebMvcAutoConfiguration.EnableWebMvcConfiguration
+ */
+public interface WebMvcRegistrations {
+
+	/**
+	 * Return the custom {@link RequestMappingHandlerMapping} that should be used and
+	 * processed by the MVC configuration.
+	 * @return the custom {@link RequestMappingHandlerMapping} instance
+	 */
+	RequestMappingHandlerMapping getRequestMappingHandlerMapping();
+
+	/**
+	 * Return the custom {@link RequestMappingHandlerAdapter} that should be used and
+	 * processed by the MVC configuration.
+	 * @return the custom {@link RequestMappingHandlerAdapter} instance
+	 */
+	RequestMappingHandlerAdapter getRequestMappingHandlerAdapter();
+
+	/**
+	 * Return the custom {@link ExceptionHandlerExceptionResolver} that should be used and
+	 * processed by the MVC configuration.
+	 * @return the custom {@link ExceptionHandlerExceptionResolver} instance
+	 */
+	ExceptionHandlerExceptionResolver getExceptionHandlerExceptionResolver();
+
+}

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

@@ -0,0 +1,47 @@
+/*
+ * Copyright 2012-2016 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 org.springframework.web.servlet.mvc.method.annotation.ExceptionHandlerExceptionResolver;
+import org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter;
+import org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping;
+
+/**
+ * An implementation of {@link WebMvcRegistrations} with empty methods allowing
+ * sub-classes to override only the methods they're interested in.
+ *
+ * @author Brian Clozel
+ * @since 1.4.0
+ */
+public class WebMvcRegistrationsAdapter implements WebMvcRegistrations {
+
+	@Override
+	public RequestMappingHandlerMapping getRequestMappingHandlerMapping() {
+		return null;
+	}
+
+	@Override
+	public RequestMappingHandlerAdapter getRequestMappingHandlerAdapter() {
+		return null;
+	}
+
+	@Override
+	public ExceptionHandlerExceptionResolver getExceptionHandlerExceptionResolver() {
+		return null;
+	}
+
+}

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

@@ -45,6 +45,7 @@ import org.springframework.boot.test.util.EnvironmentTestUtils;
 import org.springframework.boot.web.filter.OrderedHttpPutFormContentFilter;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
+import org.springframework.context.annotation.Import;
 import org.springframework.core.io.ClassPathResource;
 import org.springframework.core.io.Resource;
 import org.springframework.format.support.FormattingConversionService;
@@ -65,6 +66,7 @@ import org.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter
 import org.springframework.web.servlet.handler.SimpleUrlHandlerMapping;
 import org.springframework.web.servlet.i18n.FixedLocaleResolver;
 import org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter;
+import org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping;
 import org.springframework.web.servlet.resource.AppCacheManifestTransformer;
 import org.springframework.web.servlet.resource.CachingResourceResolver;
 import org.springframework.web.servlet.resource.CachingResourceTransformer;
@@ -468,6 +470,29 @@ public class WebMvcAutoConfigurationTests {
 						.isInstanceOf(CustomWebBindingInitializer.class);
 	}
 
+	@Test
+	public void customRequestMappingHandlerMapping() {
+		load(CustomRequestMappingHandlerMapping.class);
+		assertThat(this.context.getBean(RequestMappingHandlerMapping.class))
+				.isInstanceOf(MyRequestMappingHandlerMapping.class);
+	}
+
+	@Test
+	public void customRequestMappingHandlerAdapter() {
+		load(CustomRequestMappingHandlerAdapter.class);
+		assertThat(this.context.getBean(RequestMappingHandlerAdapter.class))
+				.isInstanceOf(MyRequestMappingHandlerAdapter.class);
+	}
+
+	@Test
+	public void multipleWebMvcRegistrations() {
+		load(MultipleWebMvcRegistrations.class);
+		assertThat(this.context.getBean(RequestMappingHandlerMapping.class))
+				.isNotInstanceOf(MyRequestMappingHandlerMapping.class);
+		assertThat(this.context.getBean(RequestMappingHandlerAdapter.class))
+				.isNotInstanceOf(MyRequestMappingHandlerAdapter.class);
+	}
+
 	private void load(Class<?> config, String... environment) {
 		this.context = new AnnotationConfigEmbeddedWebApplicationContext();
 		EnvironmentTestUtils.addEnvironment(this.context, environment);
@@ -594,4 +619,53 @@ public class WebMvcAutoConfigurationTests {
 
 	}
 
+	@Configuration
+	static class CustomRequestMappingHandlerMapping {
+
+		@Bean
+		public WebMvcRegistrationsAdapter webMvcRegistrationsHandlerMapping() {
+			return new WebMvcRegistrationsAdapter() {
+
+				@Override
+				public RequestMappingHandlerMapping getRequestMappingHandlerMapping() {
+					return new MyRequestMappingHandlerMapping();
+				}
+
+			};
+		}
+	}
+
+	private static class MyRequestMappingHandlerMapping
+			extends RequestMappingHandlerMapping {
+
+	}
+
+	@Configuration
+	static class CustomRequestMappingHandlerAdapter {
+
+		@Bean
+		public WebMvcRegistrationsAdapter webMvcRegistrationsHandlerAdapter() {
+			return new WebMvcRegistrationsAdapter() {
+
+				@Override
+				public RequestMappingHandlerAdapter getRequestMappingHandlerAdapter() {
+					return new MyRequestMappingHandlerAdapter();
+				}
+
+			};
+		}
+	}
+
+	private static class MyRequestMappingHandlerAdapter
+			extends RequestMappingHandlerAdapter {
+
+	}
+
+	@Configuration
+	@Import({ CustomRequestMappingHandlerMapping.class,
+			CustomRequestMappingHandlerAdapter.class })
+	static class MultipleWebMvcRegistrations {
+
+	}
+
 }

spring-boot-docs/src/main/asciidoc/spring-boot-features.adoc

@@ -1457,12 +1457,16 @@ The auto-configuration adds the following features on top of Spring's defaults:
 * Custom `Favicon` support.
 * Automatic use of a `ConfigurableWebBindingInitializer` bean (see below).
 
-If you want to take complete control of Spring MVC, you can add your own `@Configuration`
-annotated with `@EnableWebMvc`. If you want to keep Spring Boot MVC features, and
+If you want to keep Spring Boot MVC features, and
 you just want to add additional {spring-reference}#mvc[MVC configuration] (interceptors,
 formatters, view controllers etc.) you can add your own `@Bean` of type
-`WebMvcConfigurerAdapter`, but *without* `@EnableWebMvc`.
+`WebMvcConfigurerAdapter`, but *without* `@EnableWebMvc`. If you wish to provide custom
+instances of `RequestMappingHandlerMapping`, `RequestMappingHandlerAdapter` or
+`ExceptionHandlerExceptionResolver` you can declare a `WebMvcRegistrationsAdapter`
+instance providing such components.
 
+If you want to take complete control of Spring MVC, you can add your own `@Configuration`
+annotated with `@EnableWebMvc`.
 
 
 [[boot-features-spring-mvc-message-converters]]