Merge branch '5.1.x'

spring-web/src/main/java/org/springframework/http/client/MultipartBodyBuilder.java

@@ -26,11 +26,13 @@ import reactor.core.publisher.Mono;
 
 import org.springframework.core.ParameterizedTypeReference;
 import org.springframework.core.ResolvableType;
+import org.springframework.core.ResolvableTypeProvider;
 import org.springframework.core.io.buffer.DataBuffer;
 import org.springframework.http.HttpEntity;
 import org.springframework.http.HttpHeaders;
 import org.springframework.http.MediaType;
 import org.springframework.http.codec.multipart.Part;
+import org.springframework.lang.NonNull;
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.LinkedMultiValueMap;
@@ -272,13 +274,13 @@ public final class MultipartBodyBuilder {
 	 * @param <T> the type contained in the publisher
 	 * @param <P> the publisher
 	 */
-	public static final class PublisherEntity<T, P extends Publisher<T>> extends HttpEntity<P> {
+	public static final class PublisherEntity<T, P extends Publisher<T>> extends HttpEntity<P>
+			implements ResolvableTypeProvider  {
 
 		private final ResolvableType resolvableType;
 
-
-		private PublisherEntity(@Nullable MultiValueMap<String, String> headers, P publisher,
-				ResolvableType resolvableType) {
+		PublisherEntity(
+				@Nullable MultiValueMap<String, String> headers, P publisher, ResolvableType resolvableType) {
 
 			super(publisher, headers);
 			Assert.notNull(publisher, "'publisher' must not be null");
@@ -289,6 +291,8 @@ public final class MultipartBodyBuilder {
 		/**
 		 * Return the element type for the {@code Publisher} body.
 		 */
+		@Override
+		@NonNull
 		public ResolvableType getResolvableType() {
 			return this.resolvableType;
 		}

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

@@ -34,6 +34,7 @@ import reactor.core.publisher.Flux;
 import reactor.core.publisher.Mono;
 
 import org.springframework.core.ResolvableType;
+import org.springframework.core.ResolvableTypeProvider;
 import org.springframework.core.codec.CharSequenceEncoder;
 import org.springframework.core.codec.CodecException;
 import org.springframework.core.codec.Hints;
@@ -46,7 +47,6 @@ import org.springframework.http.HttpEntity;
 import org.springframework.http.HttpHeaders;
 import org.springframework.http.MediaType;
 import org.springframework.http.ReactiveHttpOutputMessage;
-import org.springframework.http.client.MultipartBodyBuilder;
 import org.springframework.http.codec.EncoderHttpMessageWriter;
 import org.springframework.http.codec.FormHttpMessageWriter;
 import org.springframework.http.codec.HttpMessageWriter;
@@ -265,11 +265,8 @@ public class MultipartHttpMessageWriter extends LoggingCodecSupport
 			outputHeaders.putAll(httpEntity.getHeaders());
 			body = httpEntity.getBody();
 			Assert.state(body != null, "MultipartHttpMessageWriter only supports HttpEntity with body");
-
-			if (httpEntity instanceof MultipartBodyBuilder.PublisherEntity<?, ?>) {
-				MultipartBodyBuilder.PublisherEntity<?, ?> publisherEntity =
-						(MultipartBodyBuilder.PublisherEntity<?, ?>) httpEntity;
-				resolvableType = publisherEntity.getResolvableType();
+			if (httpEntity instanceof ResolvableTypeProvider) {
+				resolvableType = ((ResolvableTypeProvider) httpEntity).getResolvableType();
 			}
 		}
 		else {