Read multipart requests from RestTestClient

Prior to this commit, the `RestTestClient` MockMvc integration would
support transforming client requests into MockMvc requests.
`RestTestClient` can serialize `MultiValueMap` request bodies as
multipart requests. In this case, the `MockMvcClientHttpRequestFactory`
would only read the body as byte stream and would not turn this into a
proper `MockMultipartHttpServletRequestBuilder`.

This commit uses the new `MultipartHttpMessageConverter` to parse the
request payload as `MockPart` instances to be added to the MockMvc
requests.

Closes gh-35569

spring-test/src/main/java/org/springframework/test/web/servlet/client/MockMvcClientHttpRequestFactory.java

@@ -16,28 +16,40 @@
 
 package org.springframework.test.web.servlet.client;
 
+import java.io.IOException;
+import java.io.InputStream;
 import java.net.URI;
 import java.nio.charset.StandardCharsets;
 import java.util.List;
 
 import jakarta.servlet.http.Cookie;
 
+import org.springframework.core.ResolvableType;
 import org.springframework.http.HttpHeaders;
 import org.springframework.http.HttpMethod;
 import org.springframework.http.HttpStatus;
 import org.springframework.http.HttpStatusCode;
+import org.springframework.http.MediaType;
 import org.springframework.http.client.ClientHttpRequest;
 import org.springframework.http.client.ClientHttpRequestFactory;
 import org.springframework.http.client.ClientHttpResponse;
+import org.springframework.http.converter.multipart.FilePart;
+import org.springframework.http.converter.multipart.MultipartHttpMessageConverter;
+import org.springframework.http.converter.multipart.Part;
+import org.springframework.mock.http.MockHttpInputMessage;
 import org.springframework.mock.http.client.MockClientHttpRequest;
 import org.springframework.mock.http.client.MockClientHttpResponse;
 import org.springframework.mock.web.MockHttpServletResponse;
+import org.springframework.mock.web.MockPart;
 import org.springframework.test.web.servlet.MockMvc;
-import org.springframework.test.web.servlet.request.MockHttpServletRequestBuilder;
+import org.springframework.test.web.servlet.request.AbstractMockHttpServletRequestBuilder;
+import org.springframework.test.web.servlet.request.MockMultipartHttpServletRequestBuilder;
 import org.springframework.util.Assert;
+import org.springframework.util.MultiValueMap;
 import org.springframework.util.ObjectUtils;
 import org.springframework.util.StringUtils;
 
+import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.multipart;
 import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.request;
 
 /**
@@ -45,10 +57,16 @@ import static org.springframework.test.web.servlet.request.MockMvcRequestBuilder
  *
  * @author Rossen Stoyanchev
  * @author Rob Worsnop
+ * @author Brian Clozel
  * @since 7.0
  */
 public class MockMvcClientHttpRequestFactory implements ClientHttpRequestFactory {
 
+	private static final ResolvableType MULTIVALUEMAP_TYPE = ResolvableType.forClassWithGenerics(MultiValueMap.class,
+			String.class, Part.class);
+
+	private static final MultipartHttpMessageConverter MULTIPART_CONVERTER = new MultipartHttpMessageConverter();
+
 	private final MockMvc mockMvc;
 
 
@@ -79,11 +97,8 @@ public class MockMvcClientHttpRequestFactory implements ClientHttpRequestFactory
 		@Override
 		public ClientHttpResponse executeInternal() {
 			try {
-				MockHttpServletRequestBuilder servletRequestBuilder = request(getMethod(), getURI())
-						.headers(getHeaders())
-						.content(getBodyAsBytes());
-
-				addCookies(servletRequestBuilder);
+				AbstractMockHttpServletRequestBuilder<?> servletRequestBuilder =
+						adaptRequest(getMethod(), getURI(), getHeaders(), getBodyAsBytes());
 
 				MockHttpServletResponse servletResponse = MockMvcClientHttpRequestFactory.this.mockMvc
 						.perform(servletRequestBuilder)
@@ -104,15 +119,61 @@ public class MockMvcClientHttpRequestFactory implements ClientHttpRequestFactory
 			}
 		}
 
-		private void addCookies(MockHttpServletRequestBuilder requestBuilder) {
-			List<String> values = getHeaders().get(HttpHeaders.COOKIE);
+		private AbstractMockHttpServletRequestBuilder<?> adaptRequest(
+				HttpMethod httpMethod, URI uri, HttpHeaders headers, byte[] bytes) throws IOException {
+
+			String contentType = headers.getFirst(HttpHeaders.CONTENT_TYPE);
+			AbstractMockHttpServletRequestBuilder<?> requestBuilder;
+
+			if (StringUtils.hasLength(contentType) &&
+					MediaType.MULTIPART_FORM_DATA.includes(MediaType.parseMediaType(contentType))) {
+
+				MockMultipartHttpServletRequestBuilder multipartRequestBuilder = multipart(httpMethod, uri);
+				Assert.notNull(bytes, "No multipart content");
+				MockHttpInputMessage inputMessage = new MockHttpInputMessage(bytes);
+				inputMessage.getHeaders().putAll(headers);
+
+				MultiValueMap<String, Part> parts = MULTIPART_CONVERTER.read(MULTIVALUEMAP_TYPE, inputMessage, null);
+				for (List<Part> partValues : parts.values()) {
+					for (Part part : partValues) {
+						parsePart(part, multipartRequestBuilder);
+					}
+				}
+				requestBuilder = multipartRequestBuilder;
+			}
+			else {
+				requestBuilder = request(httpMethod, uri);
+				if (!ObjectUtils.isEmpty(bytes)) {
+					requestBuilder.content(bytes);
+				}
+			}
+
+			requestBuilder.headers(headers);
+			addCookies(headers, requestBuilder);
+
+			return requestBuilder;
+		}
+
+		private void parsePart(Part part, MockMultipartHttpServletRequestBuilder multipartRequestBuilder) throws IOException {
+			try (InputStream content = part.content()) {
+				byte[] partBytes = content.readAllBytes();
+				MockPart mockPart = (part instanceof FilePart filePart ?
+						new MockPart(part.name(), filePart.filename(), partBytes) :
+						new MockPart(part.name(), partBytes));
+				mockPart.getHeaders().putAll(part.headers());
+				multipartRequestBuilder.part(mockPart);
+			}
+		}
+
+		private void addCookies(HttpHeaders headers, AbstractMockHttpServletRequestBuilder<?> requestBuilder) {
+			List<String> values = headers.get(HttpHeaders.COOKIE);
 			if (!ObjectUtils.isEmpty(values)) {
 				values.stream()
 						.flatMap(header -> StringUtils.commaDelimitedListToSet(header).stream())
 						.map(value -> {
-							String[] parts = StringUtils.split(value, "=");
-							Assert.isTrue(parts != null && parts.length == 2, "Invalid cookie: '" + value + "'");
-							return new Cookie(parts[0], parts[1]);
+							String[] cookieParts = StringUtils.split(value, "=");
+							Assert.isTrue(cookieParts != null && cookieParts.length == 2, "Invalid cookie: '" + value + "'");
+							return new Cookie(cookieParts[0], cookieParts[1]);
 						})
 						.forEach(requestBuilder::cookie);
 			}

spring-test/src/test/java/org/springframework/test/web/servlet/client/MockMvcRestTestClientTests.java

@@ -17,6 +17,7 @@
 package org.springframework.test.web.servlet.client;
 
 import java.io.IOException;
+import java.nio.charset.StandardCharsets;
 
 import jakarta.servlet.http.Cookie;
 import jakarta.servlet.http.HttpServletResponse;
@@ -26,6 +27,7 @@ import org.springframework.core.ParameterizedTypeReference;
 import org.springframework.core.io.ByteArrayResource;
 import org.springframework.core.io.Resource;
 import org.springframework.http.MediaType;
+import org.springframework.http.ResponseEntity;
 import org.springframework.http.converter.multipart.FilePart;
 import org.springframework.http.converter.multipart.FormFieldPart;
 import org.springframework.http.converter.multipart.Part;
@@ -35,6 +37,8 @@ import org.springframework.util.LinkedMultiValueMap;
 import org.springframework.util.MultiValueMap;
 import org.springframework.web.bind.annotation.CookieValue;
 import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.PostMapping;
+import org.springframework.web.bind.annotation.RequestParam;
 import org.springframework.web.bind.annotation.RestController;
 
 import static org.assertj.core.api.Assertions.assertThat;
@@ -106,6 +110,25 @@ class MockMvcRestTestClientTests {
 				});
 	}
 
+	@Test
+	void writeMultipart() {
+		MultiValueMap<String, Object> parts = new LinkedMultiValueMap<>();
+		parts.add("text1", "value1");
+		parts.add("file1", new ByteArrayResource("filecontent1".getBytes()) {
+			@Override
+			public String getFilename() {
+				return "spring.txt";
+			}
+		});
+
+		client.post()
+				.uri("/multipart")
+				.contentType(MediaType.MULTIPART_FORM_DATA)
+				.body(parts)
+				.exchange()
+				.expectStatus().isOk();
+	}
+
 	@RestController
 	static class TestController {
 
@@ -126,8 +149,8 @@ class MockMvcRestTestClientTests {
 			response.getWriter().write("some really bad request");
 		}
 
-		@GetMapping(value = "/multipart", produces = MediaType.MULTIPART_FORM_DATA_VALUE)
-		MultiValueMap<String, Object> multipart() {
+		@GetMapping(path = "/multipart", produces = MediaType.MULTIPART_FORM_DATA_VALUE)
+		MultiValueMap<String, Object> writeMultipart() {
 			MultiValueMap<String, Object> parts = new LinkedMultiValueMap<>();
 			parts.add("text1", "a");
 			parts.add("text2", "b");
@@ -140,6 +163,19 @@ class MockMvcRestTestClientTests {
 			parts.add("file1", resource);
 			return parts;
 		}
+
+		@PostMapping(path = "/multipart", consumes = MediaType.MULTIPART_FORM_DATA_VALUE)
+		ResponseEntity<Void> readMultipart(@RequestParam MultiValueMap<String, jakarta.servlet.http.Part> parts) throws Exception {
+			assertThat(parts.keySet()).containsOnly("text1", "file1");
+			jakarta.servlet.http.Part text1 = parts.get("text1").get(0);
+			assertThat(text1.getName()).isEqualTo("text1");
+			assertThat(text1.getInputStream()).asString(StandardCharsets.UTF_8).isEqualTo("value1");
+			jakarta.servlet.http.Part file1 = parts.get("file1").get(0);
+			assertThat(file1.getName()).isEqualTo("file1");
+			assertThat(file1.getSubmittedFileName()).isEqualTo("spring.txt");
+			assertThat(file1.getInputStream()).asString(StandardCharsets.UTF_8).isEqualTo("filecontent1");
+			return ResponseEntity.ok().build();
+		}
 	}
 
 }