Automatically alias MultipartResolver beans

Update DispatcherServletAutoConfiguration to alias a MultipartResolver
that is not named correctly. This allows the DispatcherServlet to pick
up any MultipartResolver bean, regardless of its name.

See gh-2162

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

@@ -27,7 +27,9 @@ import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
 import org.springframework.boot.autoconfigure.AutoConfigureAfter;
 import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
 import org.springframework.boot.autoconfigure.condition.ConditionOutcome;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnBean;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnWebApplication;
 import org.springframework.boot.autoconfigure.condition.SpringBootCondition;
 import org.springframework.boot.context.embedded.ServletRegistrationBean;
@@ -39,6 +41,7 @@ import org.springframework.context.annotation.Configuration;
 import org.springframework.core.Ordered;
 import org.springframework.core.annotation.Order;
 import org.springframework.core.type.AnnotatedTypeMetadata;
+import org.springframework.web.multipart.MultipartResolver;
 import org.springframework.web.servlet.DispatcherServlet;
 
 /**
@@ -94,6 +97,14 @@ public class DispatcherServletAutoConfiguration {
 			return registration;
 		}
 
+		@Bean
+		@ConditionalOnBean(MultipartResolver.class)
+		@ConditionalOnMissingBean(name = DispatcherServlet.MULTIPART_RESOLVER_BEAN_NAME)
+		public MultipartResolver multipartResolver(MultipartResolver resolver) {
+			// Detect if the user has created a MultipartResolver but named it incorrectly
+			return resolver;
+		}
+
 	}
 
 	@Order(Ordered.LOWEST_PRECEDENCE - 10)

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

@@ -30,6 +30,7 @@ import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.web.multipart.MultipartResolver;
 import org.springframework.web.multipart.support.StandardServletMultipartResolver;
+import org.springframework.web.servlet.DispatcherServlet;
 
 /**
  * {@link EnableAutoConfiguration Auto-configuration} for multi-part uploads. Adds a
@@ -55,12 +56,13 @@ public class MultipartAutoConfiguration {
 	private MultipartProperties multipartProperties = new MultipartProperties();
 
 	@Bean
-	@ConditionalOnMissingBean
+	@ConditionalOnMissingBean(value = { MultipartConfigElement.class,
+			MultipartResolver.class })
 	public MultipartConfigElement multipartConfigElement() {
 		return this.multipartProperties.createMultipartConfig();
 	}
 
-	@Bean
+	@Bean(name = DispatcherServlet.MULTIPART_RESOLVER_BEAN_NAME)
 	@ConditionalOnMissingBean(value = MultipartResolver.class)
 	public StandardServletMultipartResolver multipartResolver() {
 		return new StandardServletMultipartResolver();

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

@@ -17,6 +17,7 @@
 package org.springframework.boot.autoconfigure.web;
 
 import javax.servlet.MultipartConfigElement;
+import javax.servlet.http.HttpServletRequest;
 
 import org.junit.Test;
 import org.springframework.beans.factory.UnsatisfiedDependencyException;
@@ -25,13 +26,19 @@ import org.springframework.boot.context.embedded.ServletRegistrationBean;
 import org.springframework.boot.test.EnvironmentTestUtils;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
+import org.springframework.context.event.ContextRefreshedEvent;
 import org.springframework.mock.web.MockServletContext;
 import org.springframework.web.context.support.AnnotationConfigWebApplicationContext;
+import org.springframework.web.multipart.MultipartException;
+import org.springframework.web.multipart.MultipartHttpServletRequest;
+import org.springframework.web.multipart.MultipartResolver;
 import org.springframework.web.servlet.DispatcherServlet;
 
+import static org.hamcrest.Matchers.instanceOf;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertNotNull;
 import static org.junit.Assert.assertNull;
+import static org.junit.Assert.assertThat;
 
 /**
  * Tests for {@link DispatcherServletAutoConfiguration}.
@@ -115,6 +122,21 @@ public class DispatcherServletAutoConfigurationTests {
 		assertNotNull(registration.getMultipartConfig());
 	}
 
+	@Test
+	public void renamesMultipartResolver() throws Exception {
+		this.context = new AnnotationConfigWebApplicationContext();
+		this.context.setServletContext(new MockServletContext());
+		this.context.register(MultipartResolverConfiguration.class,
+				ServerPropertiesAutoConfiguration.class,
+				DispatcherServletAutoConfiguration.class);
+		this.context.refresh();
+		DispatcherServlet dispatcherServlet = this.context
+				.getBean(DispatcherServlet.class);
+		dispatcherServlet.onApplicationEvent(new ContextRefreshedEvent(this.context));
+		assertThat(dispatcherServlet.getMultipartResolver(),
+				instanceOf(MockMultipartResolver.class));
+	}
+
 	@Configuration
 	protected static class MultipartConfiguration {
 
@@ -130,6 +152,7 @@ public class DispatcherServletAutoConfigurationTests {
 
 	@Configuration
 	protected static class CustomDispatcherRegistration {
+
 		@Bean
 		public ServletRegistrationBean dispatcherServletRegistration() {
 			ServletRegistrationBean registration = new ServletRegistrationBean(
@@ -137,10 +160,12 @@ public class DispatcherServletAutoConfigurationTests {
 			registration.setName("customDispatcher");
 			return registration;
 		}
+
 	}
 
 	@Configuration
 	protected static class CustomAutowiredRegistration {
+
 		@Bean
 		public ServletRegistrationBean dispatcherServletRegistration(
 				DispatcherServlet dispatcherServlet) {
@@ -149,6 +174,36 @@ public class DispatcherServletAutoConfigurationTests {
 			registration.setName("customDispatcher");
 			return registration;
 		}
+
+	}
+
+	@Configuration
+	protected static class MultipartResolverConfiguration {
+
+		@Bean
+		public MultipartResolver getMultipartResolver() {
+			return new MockMultipartResolver();
+		}
+
+	}
+
+	private static class MockMultipartResolver implements MultipartResolver {
+
+		@Override
+		public boolean isMultipart(HttpServletRequest request) {
+			return false;
+		}
+
+		@Override
+		public MultipartHttpServletRequest resolveMultipart(HttpServletRequest request)
+				throws MultipartException {
+			return null;
+		}
+
+		@Override
+		public void cleanupMultipart(MultipartHttpServletRequest request) {
+		}
+
 	}
 
 }