Attempt fallback Part resolution even without StandardMultipartHttpServletRequest

Closes gh-25829

spring-web/src/main/java/org/springframework/web/multipart/support/RequestPartServletServerHttpRequest.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.
@@ -22,11 +22,13 @@ import java.io.InputStream;
 import java.nio.charset.Charset;
 
 import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.Part;
 
 import org.springframework.http.HttpHeaders;
 import org.springframework.http.MediaType;
 import org.springframework.http.server.ServerHttpRequest;
 import org.springframework.http.server.ServletServerHttpRequest;
+import org.springframework.lang.Nullable;
 import org.springframework.web.multipart.MultipartException;
 import org.springframework.web.multipart.MultipartFile;
 import org.springframework.web.multipart.MultipartHttpServletRequest;
@@ -46,59 +48,79 @@ public class RequestPartServletServerHttpRequest extends ServletServerHttpReques
 
 	private final MultipartHttpServletRequest multipartRequest;
 
-	private final String partName;
+	private final String requestPartName;
 
-	private final HttpHeaders headers;
+	private final HttpHeaders multipartHeaders;
 
 
 	/**
 	 * Create a new {@code RequestPartServletServerHttpRequest} instance.
 	 * @param request the current servlet request
-	 * @param partName the name of the part to adapt to the {@link ServerHttpRequest} contract
+	 * @param requestPartName the name of the part to adapt to the {@link ServerHttpRequest} contract
 	 * @throws MissingServletRequestPartException if the request part cannot be found
 	 * @throws MultipartException if MultipartHttpServletRequest cannot be initialized
 	 */
-	public RequestPartServletServerHttpRequest(HttpServletRequest request, String partName)
+	public RequestPartServletServerHttpRequest(HttpServletRequest request, String requestPartName)
 			throws MissingServletRequestPartException {
 
 		super(request);
 
 		this.multipartRequest = MultipartResolutionDelegate.asMultipartHttpServletRequest(request);
-		this.partName = partName;
+		this.requestPartName = requestPartName;
 
-		HttpHeaders headers = this.multipartRequest.getMultipartHeaders(this.partName);
-		if (headers == null) {
-			throw new MissingServletRequestPartException(partName);
+		HttpHeaders multipartHeaders = this.multipartRequest.getMultipartHeaders(this.requestPartName);
+		if (multipartHeaders == null) {
+			throw new MissingServletRequestPartException(requestPartName);
 		}
-		this.headers = headers;
+		this.multipartHeaders = multipartHeaders;
 	}
 
 
 	@Override
 	public HttpHeaders getHeaders() {
-		return this.headers;
+		return this.multipartHeaders;
 	}
 
 	@Override
 	public InputStream getBody() throws IOException {
-		if (this.multipartRequest instanceof StandardMultipartHttpServletRequest) {
-			try {
-				return this.multipartRequest.getPart(this.partName).getInputStream();
-			}
-			catch (Exception ex) {
-				throw new MultipartException("Could not parse multipart servlet request", ex);
+		// Prefer Servlet Part resolution to cover file as well as parameter streams
+		boolean servletParts = (this.multipartRequest instanceof StandardMultipartHttpServletRequest);
+		if (servletParts) {
+			Part part = retrieveServletPart();
+			if (part != null) {
+				return part.getInputStream();
 			}
 		}
-		else {
-			MultipartFile file = this.multipartRequest.getFile(this.partName);
-			if (file != null) {
-				return file.getInputStream();
-			}
-			else {
-				String paramValue = this.multipartRequest.getParameter(this.partName);
-				return new ByteArrayInputStream(paramValue.getBytes(determineCharset()));
+
+		// Spring-style distinction between MultipartFile and String parameters
+		MultipartFile file = this.multipartRequest.getFile(this.requestPartName);
+		if (file != null) {
+			return file.getInputStream();
+		}
+		String paramValue = this.multipartRequest.getParameter(this.requestPartName);
+		if (paramValue != null) {
+			return new ByteArrayInputStream(paramValue.getBytes(determineCharset()));
+		}
+
+		// Fallback: Servlet Part resolution even if not indicated
+		if (!servletParts) {
+			Part part = retrieveServletPart();
+			if (part != null) {
+				return part.getInputStream();
 			}
 		}
+
+		throw new IllegalStateException("No body available for request part '" + this.requestPartName + "'");
+	}
+
+	@Nullable
+	private Part retrieveServletPart() {
+		try {
+			return this.multipartRequest.getPart(this.requestPartName);
+		}
+		catch (Exception ex) {
+			throw new MultipartException("Failed to retrieve request part '" + this.requestPartName + "'", ex);
+		}
 	}
 
 	private Charset determineCharset() {

spring-web/src/test/java/org/springframework/web/multipart/support/RequestPartServletServerHttpRequestTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2019 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.
@@ -32,11 +32,13 @@ import org.springframework.mock.web.test.MockMultipartFile;
 import org.springframework.mock.web.test.MockMultipartHttpServletRequest;
 import org.springframework.util.FileCopyUtils;
 import org.springframework.web.multipart.MultipartFile;
+import org.springframework.mock.web.test.MockPart;
 
 import static org.junit.Assert.*;
 
 /**
  * @author Rossen Stoyanchev
+ * @author Juergen Hoeller
  */
 public class RequestPartServletServerHttpRequestTests {
 
@@ -137,4 +139,26 @@ public class RequestPartServletServerHttpRequestTests {
 		assertArrayEquals(bytes, result);
 	}
 
+	@Test
+	public void getBodyViaRequestPart() throws Exception {
+		MockMultipartHttpServletRequest mockRequest = new MockMultipartHttpServletRequest() {
+			@Override
+			public HttpHeaders getMultipartHeaders(String paramOrFileName) {
+				HttpHeaders headers = new HttpHeaders();
+				headers.setContentType(MediaType.APPLICATION_OCTET_STREAM);
+				return headers;
+			}
+		};
+
+		byte[] bytes = "content".getBytes("UTF-8");
+		MockPart mockPart = new MockPart("part", bytes);
+		mockPart.getHeaders().setContentType(MediaType.APPLICATION_JSON);
+		mockRequest.addPart(mockPart);
+		mockRequest.addPart(mockPart);
+		ServerHttpRequest request = new RequestPartServletServerHttpRequest(mockRequest, "part");
+
+		byte[] result = FileCopyUtils.copyToByteArray(request.getBody());
+		assertArrayEquals(bytes, result);
+	}
+
 }