Avoid matching multipart parameters annotated with `@ModelAttribute`

The ProxyHandlerMethodArgumentResolver now avoids matching multipart parameters annotated with @ModelAttribute. This allows multipart parameters to be handled by RequestParamMethodArgumentResolver which properly handles multipart arguments.

Also, the `@ProjectedPayload` annotation can now be used on parameters. This prepares for the upcoming removal of support for non-annotated projections.

Fixes #3258
Related tickets #2937
Original pull request: #3277

Signed-off-by: Chris Bono <chris.bono@broadcom.com>

src/main/java/org/springframework/data/web/ProjectedPayload.java

@@ -15,11 +15,10 @@
  */
 package org.springframework.data.web;
 
-import static java.lang.annotation.ElementType.*;
-import static java.lang.annotation.RetentionPolicy.*;
-
 import java.lang.annotation.Documented;
+import java.lang.annotation.ElementType;
 import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
 import java.lang.annotation.Target;
 
 /**
@@ -27,11 +26,12 @@ import java.lang.annotation.Target;
  * response payloads to.
  *
  * @author Oliver Gierke
+ * @author Chris Bono
  * @soundtrack
  * @since 1.13
  */
 @Documented
-@Retention(RUNTIME)
-@Target(TYPE)
+@Retention(RetentionPolicy.RUNTIME)
+@Target({ ElementType.TYPE, ElementType.PARAMETER })
 public @interface ProjectedPayload {
 }

src/main/java/org/springframework/data/web/ProxyingHandlerMethodArgumentResolver.java

@@ -36,11 +36,13 @@ import org.springframework.web.bind.support.WebDataBinderFactory;
 import org.springframework.web.context.request.NativeWebRequest;
 import org.springframework.web.method.annotation.ModelAttributeMethodProcessor;
 import org.springframework.web.method.support.HandlerMethodArgumentResolver;
+import org.springframework.web.multipart.support.MultipartResolutionDelegate;
 
 /**
  * {@link HandlerMethodArgumentResolver} to create Proxy instances for interface based controller method parameters.
  *
  * @author Oliver Gierke
+ * @author Chris Bono
  * @since 1.10
  */
 public class ProxyingHandlerMethodArgumentResolver extends ModelAttributeMethodProcessor
@@ -88,9 +90,9 @@ public class ProxyingHandlerMethodArgumentResolver extends ModelAttributeMethodP
 			return false;
 		}
 
-		// Annotated parameter
-		if (parameter.getParameterAnnotation(ProjectedPayload.class) != null
-				|| parameter.getParameterAnnotation(ModelAttribute.class) != null) {
+		// Annotated parameter (excluding multipart)
+		if ((parameter.hasParameterAnnotation(ProjectedPayload.class) || parameter.hasParameterAnnotation(
+				ModelAttribute.class)) && !MultipartResolutionDelegate.isMultipartArgument(parameter)) {
 			return true;
 		}
 

src/test/java/org/springframework/data/web/ProxyingHandlerMethodArgumentResolverUnitTests.java

@@ -27,11 +27,13 @@ import org.springframework.core.MethodParameter;
 import org.springframework.core.convert.support.DefaultConversionService;
 import org.springframework.util.ReflectionUtils;
 import org.springframework.web.bind.annotation.ModelAttribute;
+import org.springframework.web.multipart.MultipartFile;
 
 /**
  * Unit tests for {@link ProxyingHandlerMethodArgumentResolver}.
  *
  * @author Oliver Gierke
+ * @author Chris Bono
  * @soundtrack Karlijn Langendijk & Sönke Meinen - Englishman In New York (Sting,
  *             https://www.youtube.com/watch?v=O7LZsqrnaaA)
  */
@@ -88,6 +90,30 @@ class ProxyingHandlerMethodArgumentResolverUnitTests {
 		assertThat(resolver.supportsParameter(parameter)).isTrue();
 	}
 
+	@Test // GH-3258
+	void doesNotSupportAtModelAttributeForMultipartParam() throws Exception {
+
+		var parameter = getParameter("withModelAttributeMultipart", MultipartFile.class);
+
+		assertThat(resolver.supportsParameter(parameter)).isFalse();
+	}
+
+	@Test // GH-3258
+	void doesSupportAtProjectedPayload() throws Exception {
+
+		var parameter = getParameter("withProjectedPayload", SampleInterface.class);
+
+		assertThat(resolver.supportsParameter(parameter)).isTrue();
+	}
+
+	@Test // GH-3258
+	void doesNotSupportAtProjectedPayloadForMultipartParam() throws Exception {
+
+		var parameter = getParameter("withProjectedPayloadMultipart", MultipartFile.class);
+
+		assertThat(resolver.supportsParameter(parameter)).isFalse();
+	}
+
 	private static MethodParameter getParameter(String methodName, Class<?> parameterType) {
 
 		var method = ReflectionUtils.findMethod(Controller.class, methodName, parameterType);
@@ -112,5 +138,11 @@ class ProxyingHandlerMethodArgumentResolverUnitTests {
 		void withForeignAnnotation(@Autowired SampleInterface param);
 
 		void withModelAttribute(@ModelAttribute SampleInterface param);
+
+		void withModelAttributeMultipart(@ModelAttribute MultipartFile file);
+
+		void withProjectedPayload(@ProjectedPayload SampleInterface param);
+
+		void withProjectedPayloadMultipart(@ProjectedPayload MultipartFile file);
 	}
 }