Support Part/MultiPartFile arrays in ArgumentResolvers

Prior to this commit, parts of a multipart HTTP request could be
injected in @RequestPart and @RequestParam annotated arguments, when
using types:
* MultipartFile, Collection<MultiPartFile>
* javax.servlet.Part, Collection<Part>

This commits updates @RequestParam and @RequestPart argument resolvers
and now allows the array versions of those types:
* Part[]
* MultiPartFile[]

Note that the MockHtpServletRequest backing tests for standard
Servlets implementations now uses a MultiValueMap to store parts
(versus a simple hashmap).

Issue: SPR-11353

Author: bclozel

spring-web/src/main/java/org/springframework/web/method/annotation/RequestParamMethodArgumentResolver.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2013 the original author or authors.
+ * Copyright 2002-2014 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.
@@ -23,6 +23,7 @@
 import java.util.Map;
 import javax.servlet.ServletException;
 import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.Part;
 
 import org.springframework.beans.BeanUtils;
 import org.springframework.beans.factory.config.ConfigurableBeanFactory;
@@ -69,6 +70,7 @@
  *
  * @author Arjen Poutsma
  * @author Rossen Stoyanchev
+ * @author Brian Clozel
  * @since 3.1
  * @see RequestParamMapMethodArgumentResolver
  */
@@ -174,6 +176,11 @@ else if (isMultipartFileCollection(parameter)) {
 			Assert.notNull(multipartRequest, "Expected MultipartHttpServletRequest: is a MultipartResolver configured?");
 			arg = multipartRequest.getFiles(name);
 		}
+		else if(isMultipartFileArray(parameter)) {
+			assertIsMultipartRequest(servletRequest);
+			Assert.notNull(multipartRequest, "Expected MultipartHttpServletRequest: is a MultipartResolver configured?");
+			arg = multipartRequest.getFiles(name).toArray(new MultipartFile[0]);
+		}
 		else if ("javax.servlet.http.Part".equals(parameter.getParameterType().getName())) {
 			assertIsMultipartRequest(servletRequest);
 			arg = servletRequest.getPart(name);
@@ -182,6 +189,10 @@ else if (isPartCollection(parameter)) {
 			assertIsMultipartRequest(servletRequest);
 			arg = new ArrayList<Object>(servletRequest.getParts());
 		}
+		else if (isPartArray(parameter)) {
+			assertIsMultipartRequest(servletRequest);
+			arg = RequestPartResolver.resolvePart(servletRequest);
+		}
 		else {
 			arg = null;
 			if (multipartRequest != null) {
@@ -218,6 +229,16 @@ private boolean isPartCollection(MethodParameter parameter) {
 		return ((collectionType != null) && "javax.servlet.http.Part".equals(collectionType.getName()));
 	}
 
+	private boolean isPartArray(MethodParameter parameter) {
+		Class<?> paramType = parameter.getParameterType().getComponentType();
+		return ((paramType != null) && "javax.servlet.http.Part".equals(paramType.getName()));
+	}
+
+	private boolean isMultipartFileArray(MethodParameter parameter) {
+		Class<?> paramType = parameter.getParameterType().getComponentType();
+		return ((paramType != null) && MultipartFile.class.equals(paramType));
+	}
+
 	private Class<?> getCollectionParameterType(MethodParameter parameter) {
 		Class<?> paramType = parameter.getParameterType();
 		if (Collection.class.equals(paramType) || List.class.isAssignableFrom(paramType)){
@@ -277,4 +298,11 @@ public RequestParamNamedValueInfo(RequestParam annotation) {
 		}
 	}
 
+	private static class RequestPartResolver {
+
+		public static Object resolvePart(HttpServletRequest servletRequest) throws Exception {
+			return servletRequest.getParts().toArray(new Part[servletRequest.getParts().size()]);
+		}
+	}
+
 }

spring-web/src/test/java/org/springframework/mock/web/test/MockHttpServletRequest.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2013 the original author or authors.
+ * Copyright 2002-2014 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.
@@ -53,6 +53,8 @@
 
 import org.springframework.util.Assert;
 import org.springframework.util.LinkedCaseInsensitiveMap;
+import org.springframework.util.LinkedMultiValueMap;
+import org.springframework.util.MultiValueMap;
 import org.springframework.util.StringUtils;
 
 /**
@@ -66,6 +68,7 @@
  * @author Mark Fisher
  * @author Chris Beams
  * @author Sam Brannen
+ * @author Brian Clozel
  * @since 1.0.2
  */
 public class MockHttpServletRequest implements HttpServletRequest {
@@ -196,7 +199,7 @@ public class MockHttpServletRequest implements HttpServletRequest {
 
 	private boolean requestedSessionIdFromURL = false;
 
-	private final Map<String, Part> parts = new LinkedHashMap<String, Part>();
+	private final MultiValueMap<String, Part> parts = new LinkedMultiValueMap<String, Part>();
 
 
 	// ---------------------------------------------------------------------
@@ -1048,17 +1051,21 @@ public void logout() throws ServletException {
 	}
 
 	public void addPart(Part part) {
-		this.parts.put(part.getName(), part);
+		this.parts.add(part.getName(), part);
 	}
 
 	@Override
 	public Part getPart(String name) throws IOException, IllegalStateException, ServletException {
-		return this.parts.get(name);
+		return this.parts.getFirst(name);
 	}
 
 	@Override
 	public Collection<Part> getParts() throws IOException, IllegalStateException, ServletException {
-		return this.parts.values();
+		List<Part> result = new LinkedList<Part>();
+		for(List<Part> list : this.parts.values()) {
+			result.addAll(list);
+		}
+		return result;
 	}
 
 }