Fix AOT processing of @MultipartConfig annotated @WebServlet

Closes gh-37637

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/web/servlet/WebServletHandler.java

@@ -59,14 +59,18 @@ class WebServletHandler extends ServletComponentHandler {
 				: beanDefinition.getBeanClassName());
 	}
 
-	private MultipartConfigElement determineMultipartConfig(AnnotatedBeanDefinition beanDefinition) {
+	private BeanDefinition determineMultipartConfig(AnnotatedBeanDefinition beanDefinition) {
 		Map<String, Object> attributes = beanDefinition.getMetadata()
 			.getAnnotationAttributes(MultipartConfig.class.getName());
 		if (attributes == null) {
 			return null;
 		}
-		return new MultipartConfigElement((String) attributes.get("location"), (Long) attributes.get("maxFileSize"),
-				(Long) attributes.get("maxRequestSize"), (Integer) attributes.get("fileSizeThreshold"));
+		BeanDefinitionBuilder builder = BeanDefinitionBuilder.rootBeanDefinition(MultipartConfigElement.class);
+		builder.addConstructorArgValue(attributes.get("location"));
+		builder.addConstructorArgValue(attributes.get("maxFileSize"));
+		builder.addConstructorArgValue(attributes.get("maxRequestSize"));
+		builder.addConstructorArgValue(attributes.get("fileSizeThreshold"));
+		return builder.getBeanDefinition();
 	}
 
 }

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/web/servlet/ServletComponentScanRegistrarTests.java

@@ -39,6 +39,7 @@ import org.springframework.javapoet.ClassName;
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.api.Assertions.assertThatExceptionOfType;
+import static org.assertj.core.api.Assertions.assertThatNoException;
 
 /**
  * Tests for {@link ServletComponentScanRegistrar}
@@ -158,6 +159,16 @@ class ServletComponentScanRegistrarTests {
 			.accepts(generationContext.getRuntimeHints());
 	}
 
+	@Test
+	void processAheadOfTimeSucceedsForWebServletWithMultipartConfig() {
+		AnnotationConfigServletWebServerApplicationContext context = new AnnotationConfigServletWebServerApplicationContext();
+		context.registerBean(ScanServletPackage.class);
+		TestGenerationContext generationContext = new TestGenerationContext(
+				ClassName.get(getClass().getPackageName(), "TestTarget"));
+		assertThatNoException()
+			.isThrownBy(() -> new ApplicationContextAotGenerator().processAheadOfTime(context, generationContext));
+	}
+
 	@SuppressWarnings("unchecked")
 	private void compile(GenericApplicationContext context, Consumer<GenericApplicationContext> freshContext) {
 		TestGenerationContext generationContext = new TestGenerationContext(
@@ -215,4 +226,10 @@ class ServletComponentScanRegistrarTests {
 
 	}
 
+	@Configuration(proxyBeanMethods = false)
+	@ServletComponentScan("org.springframework.boot.web.servlet.testcomponents.servlet")
+	static class ScanServletPackage {
+
+	}
+
 }