Consistent support for path variable and multipart binding

Closes gh-24107
Closes gh-22169
Closes gh-25265

Author: jhoeller

spring-web/src/main/java/org/springframework/web/bind/ServletRequestDataBinder.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2020 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.
@@ -17,11 +17,14 @@
 package org.springframework.web.bind;
 
 import javax.servlet.ServletRequest;
+import javax.servlet.http.HttpServletRequest;
 
 import org.springframework.beans.MutablePropertyValues;
 import org.springframework.lang.Nullable;
+import org.springframework.util.StringUtils;
 import org.springframework.validation.BindException;
 import org.springframework.web.multipart.MultipartRequest;
+import org.springframework.web.multipart.support.StandardServletPartUtils;
 import org.springframework.web.util.WebUtils;
 
 /**
@@ -103,6 +106,12 @@ public void bind(ServletRequest request) {
 		if (multipartRequest != null) {
 			bindMultipart(multipartRequest.getMultiFileMap(), mpvs);
 		}
+		else if (StringUtils.startsWithIgnoreCase(request.getContentType(), "multipart/")) {
+			HttpServletRequest httpServletRequest = WebUtils.getNativeRequest(request, HttpServletRequest.class);
+			if (httpServletRequest != null) {
+				StandardServletPartUtils.bindParts(httpServletRequest, mpvs, isBindEmptyMultipartFiles());
+			}
+		}
 		addBindValues(mpvs, request);
 		doBind(mpvs);
 	}

spring-web/src/main/java/org/springframework/web/bind/support/WebExchangeDataBinder.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2020 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.
@@ -37,6 +37,7 @@
  * binding from URL query params or form data in the request data to Java objects.
  *
  * @author Rossen Stoyanchev
+ * @author Juergen Hoeller
  * @since 5.0
  */
 public class WebExchangeDataBinder extends WebDataBinder {
@@ -64,7 +65,7 @@ public WebExchangeDataBinder(@Nullable Object target, String objectName) {
 
 	/**
 	 * Bind query params, form data, and or multipart form data to the binder target.
-	 * @param exchange the current exchange.
+	 * @param exchange the current exchange
 	 * @return a {@code Mono<Void>} when binding is complete
 	 */
 	public Mono<Void> bind(ServerWebExchange exchange) {
@@ -76,8 +77,11 @@ public Mono<Void> bind(ServerWebExchange exchange) {
 	/**
 	 * Protected method to obtain the values for data binding. By default this
 	 * method delegates to {@link #extractValuesToBind(ServerWebExchange)}.
+	 * @param exchange the current exchange
+	 * @return a map of bind values
+	 * @since 5.3
 	 */
-	protected Mono<Map<String, Object>> getValuesToBind(ServerWebExchange exchange) {
+	public Mono<Map<String, Object>> getValuesToBind(ServerWebExchange exchange) {
 		return extractValuesToBind(exchange);
 	}
 
@@ -107,7 +111,7 @@ public static Mono<Map<String, Object>> extractValuesToBind(ServerWebExchange ex
 				});
 	}
 
-	private static void addBindValue(Map<String, Object> params, String key, List<?> values) {
+	protected static void addBindValue(Map<String, Object> params, String key, List<?> values) {
 		if (!CollectionUtils.isEmpty(values)) {
 			values = values.stream()
 					.map(value -> value instanceof FormFieldPart ? ((FormFieldPart) value).value() : value)

spring-web/src/main/java/org/springframework/web/bind/support/WebRequestDataBinder.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2020 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.
@@ -17,19 +17,16 @@
 package org.springframework.web.bind.support;
 
 import javax.servlet.http.HttpServletRequest;
-import javax.servlet.http.Part;
 
 import org.springframework.beans.MutablePropertyValues;
 import org.springframework.lang.Nullable;
-import org.springframework.util.LinkedMultiValueMap;
-import org.springframework.util.MultiValueMap;
 import org.springframework.util.StringUtils;
 import org.springframework.validation.BindException;
 import org.springframework.web.bind.WebDataBinder;
 import org.springframework.web.context.request.NativeWebRequest;
 import org.springframework.web.context.request.WebRequest;
-import org.springframework.web.multipart.MultipartException;
 import org.springframework.web.multipart.MultipartRequest;
+import org.springframework.web.multipart.support.StandardServletPartUtils;
 
 /**
  * Special {@link org.springframework.validation.DataBinder} to perform data binding
@@ -109,53 +106,21 @@ public WebRequestDataBinder(@Nullable Object target, String objectName) {
 	 */
 	public void bind(WebRequest request) {
 		MutablePropertyValues mpvs = new MutablePropertyValues(request.getParameterMap());
-		if (isMultipartRequest(request) && request instanceof NativeWebRequest) {
+		if (request instanceof NativeWebRequest) {
 			MultipartRequest multipartRequest = ((NativeWebRequest) request).getNativeRequest(MultipartRequest.class);
 			if (multipartRequest != null) {
 				bindMultipart(multipartRequest.getMultiFileMap(), mpvs);
 			}
-			else {
+			else if (StringUtils.startsWithIgnoreCase(request.getHeader("Content-Type"), "multipart/")) {
 				HttpServletRequest servletRequest = ((NativeWebRequest) request).getNativeRequest(HttpServletRequest.class);
 				if (servletRequest != null) {
-					bindParts(servletRequest, mpvs);
+					StandardServletPartUtils.bindParts(servletRequest, mpvs, isBindEmptyMultipartFiles());
 				}
 			}
 		}
 		doBind(mpvs);
 	}
 
-	/**
-	 * Check if the request is a multipart request (by checking its Content-Type header).
-	 * @param request the request with parameters to bind
-	 */
-	private boolean isMultipartRequest(WebRequest request) {
-		String contentType = request.getHeader("Content-Type");
-		return StringUtils.startsWithIgnoreCase(contentType, "multipart");
-	}
-
-	private void bindParts(HttpServletRequest request, MutablePropertyValues mpvs) {
-		try {
-			MultiValueMap<String, Part> map = new LinkedMultiValueMap<>();
-			for (Part part : request.getParts()) {
-				map.add(part.getName(), part);
-			}
-			map.forEach((key, values) -> {
-				if (values.size() == 1) {
-					Part part = values.get(0);
-					if (isBindEmptyMultipartFiles() || part.getSize() > 0) {
-						mpvs.add(key, part);
-					}
-				}
-				else {
-					mpvs.add(key, values);
-				}
-			});
-		}
-		catch (Exception ex) {
-			throw new MultipartException("Failed to get request parts", ex);
-		}
-	}
-
 	/**
 	 * Treats errors as fatal.
 	 * <p>Use this method only if it's an error if the input isn't valid.

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2020 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 +28,9 @@
 import java.util.Optional;
 import java.util.Set;
 
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.Part;
+
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 
@@ -39,6 +42,7 @@
 import org.springframework.core.annotation.AnnotationUtils;
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
+import org.springframework.util.StringUtils;
 import org.springframework.validation.BindException;
 import org.springframework.validation.BindingResult;
 import org.springframework.validation.Errors;
@@ -53,6 +57,9 @@
 import org.springframework.web.method.support.HandlerMethodArgumentResolver;
 import org.springframework.web.method.support.HandlerMethodReturnValueHandler;
 import org.springframework.web.method.support.ModelAndViewContainer;
+import org.springframework.web.multipart.MultipartFile;
+import org.springframework.web.multipart.MultipartRequest;
+import org.springframework.web.multipart.support.StandardServletPartUtils;
 
 /**
  * Resolve {@code @ModelAttribute} annotated method arguments and handle
@@ -242,15 +249,9 @@ protected Object createAttribute(String attributeName, MethodParameter parameter
 	 * @throws Exception in case of constructor invocation failure
 	 * @since 5.1
 	 */
-	@SuppressWarnings("deprecation")
 	protected Object constructAttribute(Constructor<?> ctor, String attributeName, MethodParameter parameter,
 			WebDataBinderFactory binderFactory, NativeWebRequest webRequest) throws Exception {
 
-		Object constructed = constructAttribute(ctor, attributeName, binderFactory, webRequest);
-		if (constructed != null) {
-			return constructed;
-		}
-
 		if (ctor.getParameterCount() == 0) {
 			// A single default constructor -> clearly a standard JavaBeans arrangement.
 			return BeanUtils.instantiateClass(ctor);
@@ -279,10 +280,13 @@ protected Object constructAttribute(Constructor<?> ctor, String attributeName, M
 				if (fieldDefaultPrefix != null) {
 					value = webRequest.getParameter(fieldDefaultPrefix + paramName);
 				}
-				if (value == null && fieldMarkerPrefix != null) {
-					if (webRequest.getParameter(fieldMarkerPrefix + paramName) != null) {
+				if (value == null) {
+					if (fieldMarkerPrefix != null && webRequest.getParameter(fieldMarkerPrefix + paramName) != null) {
 						value = binder.getEmptyValue(paramType);
 					}
+					else {
+						value = resolveConstructorArgument(paramName, paramType, webRequest);
+					}
 				}
 			}
 			try {
@@ -320,20 +324,6 @@ protected Object constructAttribute(Constructor<?> ctor, String attributeName, M
 		return BeanUtils.instantiateClass(ctor, args);
 	}
 
-	/**
-	 * Construct a new attribute instance with the given constructor.
-	 * @since 5.0
-	 * @deprecated as of 5.1, in favor of
-	 * {@link #constructAttribute(Constructor, String, MethodParameter, WebDataBinderFactory, NativeWebRequest)}
-	 */
-	@Deprecated
-	@Nullable
-	protected Object constructAttribute(Constructor<?> ctor, String attributeName,
-			WebDataBinderFactory binderFactory, NativeWebRequest webRequest) throws Exception {
-
-		return null;
-	}
-
 	/**
 	 * Extension point to bind the request to the target object.
 	 * @param binder the data binder instance to use for the binding
@@ -343,6 +333,29 @@ protected void bindRequestParameters(WebDataBinder binder, NativeWebRequest requ
 		((WebRequestDataBinder) binder).bind(request);
 	}
 
+	@Nullable
+	public Object resolveConstructorArgument(String paramName, Class<?> paramType, NativeWebRequest request)
+			throws Exception {
+
+		MultipartRequest multipartRequest = request.getNativeRequest(MultipartRequest.class);
+		if (multipartRequest != null) {
+			List<MultipartFile> files = multipartRequest.getFiles(paramName);
+			if (!files.isEmpty()) {
+				return (files.size() == 1 ? files.get(0) : files);
+			}
+		}
+		else if (StringUtils.startsWithIgnoreCase(request.getHeader("Content-Type"), "multipart/")) {
+			HttpServletRequest servletRequest = request.getNativeRequest(HttpServletRequest.class);
+			if (servletRequest != null) {
+				List<Part> parts = StandardServletPartUtils.getParts(servletRequest, paramName);
+				if (!parts.isEmpty()) {
+					return (parts.size() == 1 ? parts.get(0) : parts);
+				}
+			}
+		}
+		return null;
+	}
+
 	/**
 	 * Validate the model attribute if applicable.
 	 * <p>The default implementation checks for {@code @javax.validation.Valid},

spring-web/src/main/java/org/springframework/web/multipart/support/StandardServletPartUtils.java

@@ -0,0 +1,104 @@
+/*
+ * Copyright 2002-2020 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.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.web.multipart.support;
+
+import java.util.LinkedList;
+import java.util.List;
+
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.Part;
+
+import org.springframework.beans.MutablePropertyValues;
+import org.springframework.util.LinkedMultiValueMap;
+import org.springframework.util.MultiValueMap;
+import org.springframework.web.multipart.MultipartException;
+
+/**
+ * Utility methods for standard Servlet {@link Part} handling.
+ *
+ * @author Juergen Hoeller
+ * @since 5.3
+ * @see HttpServletRequest#getParts()
+ * @see StandardServletMultipartResolver
+ */
+public abstract class StandardServletPartUtils {
+
+	/**
+	 * Retrieve all parts from the given servlet request.
+	 * @param request the servlet request
+	 * @return the parts in a MultiValueMap
+	 * @throws MultipartException in case of failures
+	 */
+	public static MultiValueMap<String, Part> getParts(HttpServletRequest request) throws MultipartException {
+		try {
+			MultiValueMap<String, Part> parts = new LinkedMultiValueMap<>();
+			for (Part part : request.getParts()) {
+				parts.add(part.getName(), part);
+			}
+			return parts;
+		}
+		catch (Exception ex) {
+			throw new MultipartException("Failed to get request parts", ex);
+		}
+	}
+
+	/**
+	 * Retrieve all parts with the given name from the given servlet request.
+	 * @param request the servlet request
+	 * @param name the name to look for
+	 * @return the parts in a MultiValueMap
+	 * @throws MultipartException in case of failures
+	 */
+	public static List<Part> getParts(HttpServletRequest request, String name) throws MultipartException {
+		try {
+			List<Part> parts = new LinkedList<>();
+			for (Part part : request.getParts()) {
+				if (part.getName().equals(name)) {
+					parts.add(part);
+				}
+			}
+			return parts;
+		}
+		catch (Exception ex) {
+			throw new MultipartException("Failed to get request parts", ex);
+		}
+	}
+
+	/**
+	 * Bind all parts from the given servlet request.
+	 * @param request the servlet request
+	 * @param mpvs the property values to bind to
+	 * @param bindEmpty whether to bind empty parts as well
+	 * @throws MultipartException in case of failures
+	 */
+	public static void bindParts(HttpServletRequest request, MutablePropertyValues mpvs, boolean bindEmpty)
+			throws MultipartException {
+
+		getParts(request).forEach((key, values) -> {
+			if (values.size() == 1) {
+				Part part = values.get(0);
+				if (bindEmpty || part.getSize() > 0) {
+					mpvs.add(key, part);
+				}
+			}
+			else {
+				mpvs.add(key, values);
+			}
+		});
+	}
+
+}