Don't auto-configure MultipartConfigElement when using Commons FileUpload

Previously, when a user had declared a custom MultipartResolver bean
that is a CommonsMultipartResolver, part resolution would fail. The
failure was occurring as the servlet container was consuming the parts
before CommonsMultipartResolver had a chance to read them. This was
happening because a MultipartConfigElement was being auto-configured.

This commit updates the multipart auto-configuration so that a
MultipartConfigElement is not auto-configured when there is a
CommonsMultipartResolver bean in the context.

Closes gh-7735

Author: wilkinsona

spring-boot-autoconfigure/pom.xml

@@ -662,6 +662,11 @@
 			<artifactId>logback-classic</artifactId>
 			<scope>test</scope>
 		</dependency>
+		<dependency>
+			<groupId>commons-fileupload</groupId>
+			<artifactId>commons-fileupload</artifactId>
+			<scope>test</scope>
+		</dependency>
 		<dependency>
 			<groupId>com.atomikos</groupId>
 			<artifactId>transactions-jms</artifactId>

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2016 the original author or authors.
+ * Copyright 2012-2018 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.
@@ -28,6 +28,7 @@
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.web.multipart.MultipartResolver;
+import org.springframework.web.multipart.commons.CommonsMultipartResolver;
 import org.springframework.web.multipart.support.StandardServletMultipartResolver;
 import org.springframework.web.servlet.DispatcherServlet;
 
@@ -59,7 +60,8 @@ public MultipartAutoConfiguration(MultipartProperties multipartProperties) {
 	}
 
 	@Bean
-	@ConditionalOnMissingBean
+	@ConditionalOnMissingBean({ MultipartConfigElement.class,
+			CommonsMultipartResolver.class })
 	public MultipartConfigElement multipartConfigElement() {
 		return this.multipartProperties.createMultipartConfig();
 	}

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

@@ -49,6 +49,7 @@
 import org.springframework.web.bind.annotation.ResponseBody;
 import org.springframework.web.client.RestTemplate;
 import org.springframework.web.multipart.MultipartResolver;
+import org.springframework.web.multipart.commons.CommonsMultipartResolver;
 import org.springframework.web.multipart.support.StandardServletMultipartResolver;
 import org.springframework.web.servlet.DispatcherServlet;
 import org.springframework.web.servlet.config.annotation.EnableWebMvc;
@@ -200,6 +201,17 @@ public void containerWithCustomMultipartResolver() throws Exception {
 				.getBean(MultipartResolver.class);
 		assertThat(multipartResolver)
 				.isNotInstanceOf(StandardServletMultipartResolver.class);
+		assertThat(this.context.getBeansOfType(MultipartConfigElement.class)).hasSize(1);
+	}
+
+	@Test
+	public void containerWithCommonsMultipartResolver() throws Exception {
+		this.context = new AnnotationConfigEmbeddedWebApplicationContext(
+				ContainerWithCommonsMultipartResolver.class, BaseConfiguration.class);
+		MultipartResolver multipartResolver = this.context
+				.getBean(MultipartResolver.class);
+		assertThat(multipartResolver).isInstanceOf(CommonsMultipartResolver.class);
+		assertThat(this.context.getBeansOfType(MultipartConfigElement.class)).hasSize(0);
 	}
 
 	@Test
@@ -370,6 +382,15 @@ MultipartResolver multipartResolver() {
 
 	}
 
+	public static class ContainerWithCommonsMultipartResolver {
+
+		@Bean
+		CommonsMultipartResolver multipartResolver() {
+			return mock(CommonsMultipartResolver.class);
+		}
+
+	}
+
 	@Controller
 	public static class WebController {
 

spring-boot-parent/pom.xml

@@ -54,6 +54,11 @@
 				<artifactId>log4j</artifactId>
 				<version>1.2.17</version>
 			</dependency>
+			<dependency>
+				<groupId>commons-fileupload</groupId>
+				<artifactId>commons-fileupload</artifactId>
+				<version>1.3.3</version>
+			</dependency>
 			<dependency>
 				<groupId>com.google.guava</groupId>
 				<artifactId>guava</artifactId>