Add multipart support for MockMvcTester

File uploads with MockMvc require a separate
MockHttpServletRequestBuilder implementation. This commit applies the
same change to support AssertJ on this builder, but for the multipart
version.

Any request builder can now use `multipart()` to "down cast" to a
dedicated multipart request builder that contains the settings
configured thus far.

Closes gh-33027

spring-test/src/main/java/org/springframework/test/web/servlet/assertj/MockMvcTester.java

@@ -31,10 +31,12 @@ import org.springframework.http.converter.GenericHttpMessageConverter;
 import org.springframework.http.converter.HttpMessageConverter;
 import org.springframework.lang.Nullable;
 import org.springframework.mock.web.MockHttpServletRequest;
+import org.springframework.mock.web.MockMultipartHttpServletRequest;
 import org.springframework.test.web.servlet.MockMvc;
 import org.springframework.test.web.servlet.MvcResult;
 import org.springframework.test.web.servlet.RequestBuilder;
 import org.springframework.test.web.servlet.request.AbstractMockHttpServletRequestBuilder;
+import org.springframework.test.web.servlet.request.AbstractMockMultipartHttpServletRequestBuilder;
 import org.springframework.test.web.servlet.request.MockMvcRequestBuilders;
 import org.springframework.test.web.servlet.setup.DefaultMockMvcBuilder;
 import org.springframework.test.web.servlet.setup.MockMvcBuilders;
@@ -389,8 +391,42 @@ public final class MockMvcTester {
 	public final class MockMvcRequestBuilder extends AbstractMockHttpServletRequestBuilder<MockMvcRequestBuilder>
 			implements AssertProvider<MvcTestResultAssert> {
 
+		private final HttpMethod httpMethod;
+
 		private MockMvcRequestBuilder(HttpMethod httpMethod) {
 			super(httpMethod);
+			this.httpMethod = httpMethod;
+		}
+
+		/**
+		 * Enable file upload support using multipart.
+		 * @return a {@link MockMultipartMvcRequestBuilder} with the settings
+		 * configured thus far
+		 */
+		public MockMultipartMvcRequestBuilder multipart() {
+			return new MockMultipartMvcRequestBuilder(this);
+		}
+
+		public MvcTestResult exchange() {
+			return perform(this);
+		}
+
+		@Override
+		public MvcTestResultAssert assertThat() {
+			return new MvcTestResultAssert(exchange(), MockMvcTester.this.jsonMessageConverter);
+		}
+	}
+
+	/**
+	 * A builder for {@link MockMultipartHttpServletRequest} that supports AssertJ.
+	 */
+	public final class MockMultipartMvcRequestBuilder
+			extends AbstractMockMultipartHttpServletRequestBuilder<MockMultipartMvcRequestBuilder>
+			implements AssertProvider<MvcTestResultAssert> {
+
+		private MockMultipartMvcRequestBuilder(MockMvcRequestBuilder currentBuilder) {
+			super(currentBuilder.httpMethod);
+			merge(currentBuilder);
 		}
 
 		public MvcTestResult exchange() {

spring-test/src/main/java/org/springframework/test/web/servlet/request/AbstractMockMultipartHttpServletRequestBuilder.java

@@ -0,0 +1,159 @@
+/*
+ * Copyright 2002-2024 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.test.web.servlet.request;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.InputStreamReader;
+import java.nio.charset.Charset;
+import java.nio.charset.StandardCharsets;
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.List;
+
+import jakarta.servlet.ServletContext;
+import jakarta.servlet.http.Part;
+
+import org.springframework.http.HttpMethod;
+import org.springframework.http.MediaType;
+import org.springframework.lang.Nullable;
+import org.springframework.mock.web.MockHttpServletRequest;
+import org.springframework.mock.web.MockMultipartFile;
+import org.springframework.mock.web.MockMultipartHttpServletRequest;
+import org.springframework.util.Assert;
+import org.springframework.util.FileCopyUtils;
+import org.springframework.util.LinkedMultiValueMap;
+import org.springframework.util.MultiValueMap;
+
+/**
+ * Base builder for {@link MockMultipartHttpServletRequest}.
+ *
+ * @author Rossen Stoyanchev
+ * @author Arjen Poutsma
+ * @author Stephane Nicoll
+ * @since 6.2
+ * @param <B> a self reference to the builder type
+ */
+public abstract class AbstractMockMultipartHttpServletRequestBuilder<B extends AbstractMockMultipartHttpServletRequestBuilder<B>>
+		extends AbstractMockHttpServletRequestBuilder<B> {
+
+	private final List<MockMultipartFile> files = new ArrayList<>();
+
+	private final MultiValueMap<String, Part> parts = new LinkedMultiValueMap<>();
+
+
+	protected AbstractMockMultipartHttpServletRequestBuilder(HttpMethod httpMethod) {
+		super(httpMethod);
+	}
+
+	/**
+	 * Add a new {@link MockMultipartFile} with the given content.
+	 * @param name the name of the file
+	 * @param content the content of the file
+	 */
+	public B file(String name, byte[] content) {
+		this.files.add(new MockMultipartFile(name, content));
+		return self();
+	}
+
+	/**
+	 * Add the given {@link MockMultipartFile}.
+	 * @param file the multipart file
+	 */
+	public B file(MockMultipartFile file) {
+		this.files.add(file);
+		return self();
+	}
+
+	/**
+	 * Add {@link Part} components to the request.
+	 * @param parts one or more parts to add
+	 * @since 5.0
+	 */
+	public B part(Part... parts) {
+		Assert.notEmpty(parts, "'parts' must not be empty");
+		for (Part part : parts) {
+			this.parts.add(part.getName(), part);
+		}
+		return self();
+	}
+
+	@Override
+	public Object merge(@Nullable Object parent) {
+		if (parent == null) {
+			return this;
+		}
+		if (parent instanceof AbstractMockHttpServletRequestBuilder<?>) {
+			super.merge(parent);
+			if (parent instanceof AbstractMockMultipartHttpServletRequestBuilder<?> parentBuilder) {
+				this.files.addAll(parentBuilder.files);
+				parentBuilder.parts.keySet().forEach(name ->
+						this.parts.putIfAbsent(name, parentBuilder.parts.get(name)));
+			}
+		}
+		else {
+			throw new IllegalArgumentException("Cannot merge with [" + parent.getClass().getName() + "]");
+		}
+		return this;
+	}
+
+	/**
+	 * Create a new {@link MockMultipartHttpServletRequest} based on the
+	 * supplied {@code ServletContext} and the {@code MockMultipartFiles}
+	 * added to this builder.
+	 */
+	@Override
+	protected final MockHttpServletRequest createServletRequest(ServletContext servletContext) {
+		MockMultipartHttpServletRequest request = new MockMultipartHttpServletRequest(servletContext);
+		Charset defaultCharset = (request.getCharacterEncoding() != null ?
+				Charset.forName(request.getCharacterEncoding()) : StandardCharsets.UTF_8);
+
+		this.files.forEach(request::addFile);
+		this.parts.values().stream().flatMap(Collection::stream).forEach(part -> {
+			request.addPart(part);
+			try {
+				String name = part.getName();
+				String filename = part.getSubmittedFileName();
+				InputStream is = part.getInputStream();
+				if (filename != null) {
+					request.addFile(new MockMultipartFile(name, filename, part.getContentType(), is));
+				}
+				else {
+					InputStreamReader reader = new InputStreamReader(is, getCharsetOrDefault(part, defaultCharset));
+					String value = FileCopyUtils.copyToString(reader);
+					request.addParameter(part.getName(), value);
+				}
+			}
+			catch (IOException ex) {
+				throw new IllegalStateException("Failed to read content for part " + part.getName(), ex);
+			}
+		});
+
+		return request;
+	}
+
+	private Charset getCharsetOrDefault(Part part, Charset defaultCharset) {
+		if (part.getContentType() != null) {
+			MediaType mediaType = MediaType.parseMediaType(part.getContentType());
+			if (mediaType.getCharset() != null) {
+				return mediaType.getCharset();
+			}
+		}
+		return defaultCharset;
+	}
+
+}

spring-test/src/main/java/org/springframework/test/web/servlet/request/MockMultipartHttpServletRequestBuilder.java

@@ -16,42 +16,22 @@
 
 package org.springframework.test.web.servlet.request;
 
-import java.io.IOException;
-import java.io.InputStream;
-import java.io.InputStreamReader;
 import java.net.URI;
-import java.nio.charset.Charset;
-import java.nio.charset.StandardCharsets;
-import java.util.ArrayList;
-import java.util.Collection;
-import java.util.List;
-
-import jakarta.servlet.ServletContext;
-import jakarta.servlet.http.Part;
 
 import org.springframework.http.HttpMethod;
 import org.springframework.http.MediaType;
-import org.springframework.lang.Nullable;
-import org.springframework.mock.web.MockHttpServletRequest;
-import org.springframework.mock.web.MockMultipartFile;
 import org.springframework.mock.web.MockMultipartHttpServletRequest;
-import org.springframework.util.Assert;
-import org.springframework.util.FileCopyUtils;
-import org.springframework.util.LinkedMultiValueMap;
-import org.springframework.util.MultiValueMap;
 
 /**
  * Default builder for {@link MockMultipartHttpServletRequest}.
  *
  * @author Rossen Stoyanchev
  * @author Arjen Poutsma
+ * @author Stephane Nicoll
  * @since 3.2
  */
-public class MockMultipartHttpServletRequestBuilder extends AbstractMockHttpServletRequestBuilder<MockMultipartHttpServletRequestBuilder> {
+public class MockMultipartHttpServletRequestBuilder
-
+		extends AbstractMockMultipartHttpServletRequestBuilder<MockMultipartHttpServletRequestBuilder> {
-	private final List<MockMultipartFile> files = new ArrayList<>();
-
-	private final MultiValueMap<String, Part> parts = new LinkedMultiValueMap<>();
 
 
 	/**
@@ -98,101 +78,4 @@ public class MockMultipartHttpServletRequestBuilder extends AbstractMockHttpServ
 		super.contentType(MediaType.MULTIPART_FORM_DATA);
 	}
 
-
-	/**
-	 * Add a new {@link MockMultipartFile} with the given content.
-	 * @param name the name of the file
-	 * @param content the content of the file
-	 */
-	public MockMultipartHttpServletRequestBuilder file(String name, byte[] content) {
-		this.files.add(new MockMultipartFile(name, content));
-		return this;
-	}
-
-	/**
-	 * Add the given {@link MockMultipartFile}.
-	 * @param file the multipart file
-	 */
-	public MockMultipartHttpServletRequestBuilder file(MockMultipartFile file) {
-		this.files.add(file);
-		return this;
-	}
-
-	/**
-	 * Add {@link Part} components to the request.
-	 * @param parts one or more parts to add
-	 * @since 5.0
-	 */
-	public MockMultipartHttpServletRequestBuilder part(Part... parts) {
-		Assert.notEmpty(parts, "'parts' must not be empty");
-		for (Part part : parts) {
-			this.parts.add(part.getName(), part);
-		}
-		return this;
-	}
-
-	@Override
-	public Object merge(@Nullable Object parent) {
-		if (parent == null) {
-			return this;
-		}
-		if (parent instanceof AbstractMockHttpServletRequestBuilder) {
-			super.merge(parent);
-			if (parent instanceof MockMultipartHttpServletRequestBuilder parentBuilder) {
-				this.files.addAll(parentBuilder.files);
-				parentBuilder.parts.keySet().forEach(name ->
-						this.parts.putIfAbsent(name, parentBuilder.parts.get(name)));
-			}
-		}
-		else {
-			throw new IllegalArgumentException("Cannot merge with [" + parent.getClass().getName() + "]");
-		}
-		return this;
-	}
-
-	/**
-	 * Create a new {@link MockMultipartHttpServletRequest} based on the
-	 * supplied {@code ServletContext} and the {@code MockMultipartFiles}
-	 * added to this builder.
-	 */
-	@Override
-	protected final MockHttpServletRequest createServletRequest(ServletContext servletContext) {
-		MockMultipartHttpServletRequest request = new MockMultipartHttpServletRequest(servletContext);
-		Charset defaultCharset = (request.getCharacterEncoding() != null ?
-				Charset.forName(request.getCharacterEncoding()) : StandardCharsets.UTF_8);
-
-		this.files.forEach(request::addFile);
-		this.parts.values().stream().flatMap(Collection::stream).forEach(part -> {
-			request.addPart(part);
-			try {
-				String name = part.getName();
-				String filename = part.getSubmittedFileName();
-				InputStream is = part.getInputStream();
-				if (filename != null) {
-					request.addFile(new MockMultipartFile(name, filename, part.getContentType(), is));
-				}
-				else {
-					InputStreamReader reader = new InputStreamReader(is, getCharsetOrDefault(part, defaultCharset));
-					String value = FileCopyUtils.copyToString(reader);
-					request.addParameter(part.getName(), value);
-				}
-			}
-			catch (IOException ex) {
-				throw new IllegalStateException("Failed to read content for part " + part.getName(), ex);
-			}
-		});
-
-		return request;
-	}
-
-	private Charset getCharsetOrDefault(Part part, Charset defaultCharset) {
-		if (part.getContentType() != null) {
-			MediaType mediaType = MediaType.parseMediaType(part.getContentType());
-			if (mediaType.getCharset() != null) {
-				return mediaType.getCharset();
-			}
-		}
-		return defaultCharset;
-	}
-
 }

spring-test/src/test/java/org/springframework/test/web/servlet/assertj/MockMvcTesterIntegrationTests.java

@@ -20,6 +20,7 @@ import java.io.ByteArrayOutputStream;
 import java.io.PrintStream;
 import java.nio.charset.StandardCharsets;
 import java.util.Collections;
+import java.util.HashMap;
 import java.util.List;
 import java.util.Locale;
 import java.util.Map;
@@ -31,6 +32,7 @@ import jakarta.servlet.ServletException;
 import jakarta.servlet.http.Cookie;
 import jakarta.servlet.http.HttpServletRequest;
 import jakarta.servlet.http.HttpServletResponse;
+import jakarta.servlet.http.Part;
 import jakarta.validation.Valid;
 import jakarta.validation.constraints.Size;
 import org.junit.jupiter.api.AfterEach;
@@ -44,6 +46,8 @@ import org.springframework.core.io.ClassPathResource;
 import org.springframework.http.HttpHeaders;
 import org.springframework.http.HttpStatus;
 import org.springframework.http.MediaType;
+import org.springframework.mock.web.MockMultipartFile;
+import org.springframework.mock.web.MockPart;
 import org.springframework.stereotype.Controller;
 import org.springframework.test.context.junit.jupiter.web.SpringJUnitWebConfig;
 import org.springframework.test.web.Person;
@@ -54,13 +58,19 @@ import org.springframework.web.bind.annotation.GetMapping;
 import org.springframework.web.bind.annotation.ModelAttribute;
 import org.springframework.web.bind.annotation.PathVariable;
 import org.springframework.web.bind.annotation.PostMapping;
+import org.springframework.web.bind.annotation.PutMapping;
 import org.springframework.web.bind.annotation.RequestMapping;
+import org.springframework.web.bind.annotation.RequestParam;
+import org.springframework.web.bind.annotation.RequestPart;
 import org.springframework.web.bind.annotation.RestController;
 import org.springframework.web.bind.annotation.SessionAttributes;
 import org.springframework.web.context.WebApplicationContext;
+import org.springframework.web.multipart.MultipartFile;
+import org.springframework.web.multipart.support.MissingServletRequestPartException;
 import org.springframework.web.server.ResponseStatusException;
 import org.springframework.web.servlet.DispatcherServlet;
 import org.springframework.web.servlet.HandlerInterceptor;
+import org.springframework.web.servlet.ModelAndView;
 import org.springframework.web.servlet.config.annotation.EnableWebMvc;
 import org.springframework.web.servlet.mvc.support.RedirectAttributes;
 
@@ -113,6 +123,41 @@ public class MockMvcTesterIntegrationTests {
 		}
 	}
 
+	@Nested
+	class MultipartTests {
+
+		private final MockMultipartFile JSON_PART_FILE = new MockMultipartFile("json", "json", "application/json", """
+				{
+					"name": "test"
+				}""".getBytes(StandardCharsets.UTF_8));
+
+		@Test
+		void multipartWithPut() {
+			MockMultipartFile part = new MockMultipartFile("file", "content.txt", null, "value".getBytes(StandardCharsets.UTF_8));
+			assertThat(mvc.put().uri("/multipart-put").multipart().file(part).file(JSON_PART_FILE))
+					.hasStatusOk()
+					.hasViewName("index")
+					.model().contains(entry("name", "file"));
+		}
+
+		@Test
+		void multipartWithMissingPart() {
+			assertThat(mvc.put().uri("/multipart-put").multipart().file(JSON_PART_FILE))
+					.hasStatus(HttpStatus.BAD_REQUEST)
+					.failure().isInstanceOfSatisfying(MissingServletRequestPartException.class,
+							ex -> assertThat(ex.getRequestPartName()).isEqualTo("file"));
+		}
+
+		@Test
+		void multipartWithNamedPart() {
+			MockPart part = new MockPart("part", "content.txt", "value".getBytes(StandardCharsets.UTF_8));
+			assertThat(mvc.post().uri("/part").multipart().part(part).file(JSON_PART_FILE))
+					.hasStatusOk()
+					.hasViewName("index")
+					.model().contains(entry("part", "content.txt"), entry("name", "test"));
+		}
+	}
+
 	@Nested
 	class CookieTests {
 
@@ -516,7 +561,7 @@ public class MockMvcTesterIntegrationTests {
 	@Configuration
 	@EnableWebMvc
 	@Import({ TestController.class, PersonController.class, AsyncController.class,
-			SessionController.class, ErrorController.class })
+			MultipartController.class, SessionController.class, ErrorController.class })
 	static class WebConfiguration {
 	}
 
@@ -564,6 +609,22 @@ public class MockMvcTesterIntegrationTests {
 		}
 	}
 
+	@Controller
+	static class MultipartController {
+
+		@PostMapping("/part")
+		ModelAndView part(@RequestPart Part part, @RequestPart Map<String, String> json) {
+			Map<String, Object> model = new HashMap<>(json);
+			model.put(part.getName(), part.getSubmittedFileName());
+			return new ModelAndView("index", model);
+		}
+
+		@PutMapping("/multipart-put")
+		public ModelAndView multiPartViaHttpPut(@RequestParam MultipartFile file) {
+			return new ModelAndView("index", Map.of("name", file.getName()));
+		}
+	}
+
 	@Controller
 	@SessionAttributes("locale")
 	static class SessionController {