Reasonable defaults for MultipartHttpMessageWriter

MultipartHttpMessageWriter is now configured to handle JSON and XML
out of the box.

spring-web/src/main/java/org/springframework/http/codec/AbstractCodecConfigurer.java

@@ -65,6 +65,7 @@ abstract class AbstractCodecConfigurer implements CodecConfigurer {
 	protected AbstractCodecConfigurer(AbstractDefaultCodecs defaultCodecs) {
 		Assert.notNull(defaultCodecs, "'defaultCodecs' is required.");
 		this.defaultCodecs = defaultCodecs;
+		this.defaultCodecs.setCustomCodecs(this.customCodecs);
 	}
 
 
@@ -112,7 +113,7 @@ abstract class AbstractCodecConfigurer implements CodecConfigurer {
 	}
 
 
-	abstract static class AbstractDefaultCodecs implements DefaultCodecs {
+	abstract protected static class AbstractDefaultCodecs implements DefaultCodecs {
 
 		private boolean registerDefaults = true;
 
@@ -120,6 +121,8 @@ abstract class AbstractCodecConfigurer implements CodecConfigurer {
 
 		private Jackson2JsonEncoder jackson2Encoder;
 
+		private DefaultCustomCodecs customCodecs;
+
 
 		public void setRegisterDefaults(boolean registerDefaults) {
 			this.registerDefaults = registerDefaults;
@@ -129,6 +132,17 @@ abstract class AbstractCodecConfigurer implements CodecConfigurer {
 			return this.registerDefaults;
 		}
 
+		/**
+		 * Access to custom codecs for sub-classes, e.g. for multipart writers.
+		 */
+		public void setCustomCodecs(DefaultCustomCodecs customCodecs) {
+			this.customCodecs = customCodecs;
+		}
+
+		public DefaultCustomCodecs getCustomCodecs() {
+			return this.customCodecs;
+		}
+
 		@Override
 		public void jackson2Decoder(Jackson2JsonDecoder decoder) {
 			this.jackson2Decoder = decoder;
@@ -227,7 +241,7 @@ abstract class AbstractCodecConfigurer implements CodecConfigurer {
 	}
 
 
-	private static class DefaultCustomCodecs implements CustomCodecs {
+	protected static class DefaultCustomCodecs implements CustomCodecs {
 
 		private final List<HttpMessageReader<?>> typedReaders = new ArrayList<>();
 		private final List<HttpMessageWriter<?>> typedWriters = new ArrayList<>();

spring-web/src/main/java/org/springframework/http/codec/DefaultClientCodecConfigurer.java

@@ -100,9 +100,19 @@ class DefaultClientCodecConfigurer extends AbstractCodecConfigurer implements Cl
 		}
 
 		private MultipartHttpMessageWriter getMultipartHttpMessageWriter() {
-			return this.multipartCodecs != null ?
-					new MultipartHttpMessageWriter(this.multipartCodecs.getWriters()) :
-					new MultipartHttpMessageWriter();
+			List<HttpMessageWriter<?>> partWriters;
+			if (this.multipartCodecs != null) {
+				partWriters = this.multipartCodecs.getWriters();
+			}
+			else {
+				partWriters = new ArrayList<>();
+				partWriters.addAll(super.getTypedWriters());
+				partWriters.addAll(getCustomCodecs().getTypedWriters());
+				partWriters.addAll(super.getObjectWriters());
+				partWriters.addAll(getCustomCodecs().getObjectWriters());
+				partWriters.addAll(super.getCatchAllWriters());
+			}
+			return new MultipartHttpMessageWriter(partWriters);
 		}
 	}
 

spring-webflux/src/test/java/org/springframework/web/reactive/result/method/annotation/MultipartIntegrationTests.java

@@ -30,14 +30,11 @@ import reactor.test.StepVerifier;
 import org.springframework.context.annotation.AnnotationConfigApplicationContext;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
-import org.springframework.core.codec.CharSequenceEncoder;
 import org.springframework.core.io.ClassPathResource;
 import org.springframework.http.HttpEntity;
 import org.springframework.http.HttpHeaders;
 import org.springframework.http.HttpStatus;
 import org.springframework.http.MediaType;
-import org.springframework.http.codec.ResourceHttpMessageWriter;
-import org.springframework.http.codec.json.Jackson2JsonEncoder;
 import org.springframework.http.codec.multipart.FilePart;
 import org.springframework.http.codec.multipart.FormFieldPart;
 import org.springframework.http.codec.multipart.MultipartHttpMessageReader;
@@ -55,7 +52,6 @@ import org.springframework.web.reactive.DispatcherHandler;
 import org.springframework.web.reactive.config.EnableWebFlux;
 import org.springframework.web.reactive.function.BodyInserters;
 import org.springframework.web.reactive.function.client.ClientResponse;
-import org.springframework.web.reactive.function.client.ExchangeStrategies;
 import org.springframework.web.reactive.function.client.WebClient;
 import org.springframework.web.server.adapter.WebHttpHandlerBuilder;
 
@@ -70,16 +66,7 @@ public class MultipartIntegrationTests extends AbstractHttpHandlerIntegrationTes
 	@Before
 	public void setup() throws Exception {
 		super.setup();
-
-		ExchangeStrategies strategies = ExchangeStrategies.builder().defaultCodecs(configurer ->
-				configurer.multipartCodecs()
-						.encoder(CharSequenceEncoder.allMimeTypes())
-						.writer(new ResourceHttpMessageWriter())
-						.encoder(new Jackson2JsonEncoder())).build();
-
-		this.webClient = WebClient.builder().baseUrl("http://localhost:" + this.port)
-				.exchangeStrategies(strategies)
-				.build();
+		this.webClient = WebClient.create("http://localhost:" + this.port);
 	}