Support filename hint for client side too

Closes gh-25516

Author: rstoyanchev

spring-web/src/main/java/org/springframework/http/codec/DecoderHttpMessageReader.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.
@@ -96,13 +96,15 @@ public boolean canRead(ResolvableType elementType, @Nullable MediaType mediaType
 	@Override
 	public Flux<T> read(ResolvableType elementType, ReactiveHttpInputMessage message, Map<String, Object> hints) {
 		MediaType contentType = getContentType(message);
-		return this.decoder.decode(message.getBody(), elementType, contentType, hints);
+		Map<String, Object> allHints = Hints.merge(hints, getReadHints(elementType, message));
+		return this.decoder.decode(message.getBody(), elementType, contentType, allHints);
 	}
 
 	@Override
 	public Mono<T> readMono(ResolvableType elementType, ReactiveHttpInputMessage message, Map<String, Object> hints) {
 		MediaType contentType = getContentType(message);
-		return this.decoder.decodeToMono(message.getBody(), elementType, contentType, hints);
+		Map<String, Object> allHints = Hints.merge(hints, getReadHints(elementType, message));
+		return this.decoder.decodeToMono(message.getBody(), elementType, contentType, allHints);
 	}
 
 	/**
@@ -118,6 +120,14 @@ protected MediaType getContentType(HttpMessage inputMessage) {
 		return (contentType != null ? contentType : MediaType.APPLICATION_OCTET_STREAM);
 	}
 
+	/**
+	 * Get additional hints for decoding based on the input HTTP message.
+	 * @since 5.3
+	 */
+	protected Map<String, Object> getReadHints(ResolvableType elementType, ReactiveHttpInputMessage message) {
+		return Hints.none();
+	}
+
 
 	// Server-side only...
 

spring-web/src/main/java/org/springframework/http/codec/ResourceHttpMessageReader.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.
@@ -22,6 +22,7 @@
 import org.springframework.core.codec.Hints;
 import org.springframework.core.codec.ResourceDecoder;
 import org.springframework.core.io.Resource;
+import org.springframework.http.ReactiveHttpInputMessage;
 import org.springframework.http.server.reactive.ServerHttpRequest;
 import org.springframework.http.server.reactive.ServerHttpResponse;
 import org.springframework.util.StringUtils;
@@ -45,12 +46,18 @@ public ResourceHttpMessageReader(ResourceDecoder resourceDecoder) {
 	}
 
 
+	@Override
+	protected Map<String, Object> getReadHints(ResolvableType elementType, ReactiveHttpInputMessage message) {
+		String filename = message.getHeaders().getContentDisposition().getFilename();
+		return (StringUtils.hasText(filename) ?
+				Hints.from(ResourceDecoder.FILENAME_HINT, filename) : Hints.none());
+	}
+
 	@Override
 	protected Map<String, Object> getReadHints(ResolvableType actualType, ResolvableType elementType,
 			ServerHttpRequest request, ServerHttpResponse response) {
 
-		String name = request.getHeaders().getContentDisposition().getFilename();
-		return StringUtils.hasText(name) ? Hints.from(ResourceDecoder.FILENAME_HINT, name) : Hints.none();
+		return getReadHints(elementType, request);
 	}
 
 }

spring-web/src/test/java/org/springframework/http/codec/ResourceHttpMessageReaderTests.java

@@ -0,0 +1,73 @@
+/*
+ * 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.
+ * 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.http.codec;
+
+import java.io.IOException;
+import java.nio.charset.StandardCharsets;
+import java.util.Collections;
+
+import org.junit.jupiter.api.Test;
+import reactor.core.publisher.Mono;
+
+import org.springframework.core.ResolvableType;
+import org.springframework.core.io.ByteArrayResource;
+import org.springframework.core.io.Resource;
+import org.springframework.core.io.buffer.DataBuffer;
+import org.springframework.core.testfixture.io.buffer.AbstractLeakCheckingTests;
+import org.springframework.http.ContentDisposition;
+import org.springframework.http.HttpStatus;
+import org.springframework.http.MediaType;
+import org.springframework.web.testfixture.http.client.reactive.MockClientHttpResponse;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Unit tests for {@link ResourceHttpMessageReader}.
+ * @author Rossen Stoyanchev
+ */
+public class ResourceHttpMessageReaderTests extends AbstractLeakCheckingTests {
+
+	private final ResourceHttpMessageReader reader = new ResourceHttpMessageReader();
+
+	@Test
+	void readResourceAsMono() throws IOException {
+		String filename = "test.txt";
+		String body = "Test resource content";
+
+		ContentDisposition contentDisposition =
+				ContentDisposition.builder("attachment").name("file").filename(filename).build();
+
+		MockClientHttpResponse response = new MockClientHttpResponse(HttpStatus.OK);
+		response.getHeaders().setContentType(MediaType.TEXT_PLAIN);
+		response.getHeaders().setContentDisposition(contentDisposition);
+		response.setBody(Mono.just(stringBuffer(body)));
+
+		Resource resource = reader.readMono(
+				ResolvableType.forClass(ByteArrayResource.class), response, Collections.emptyMap()).block();
+
+		assertThat(resource).isNotNull();
+		assertThat(resource.getFilename()).isEqualTo(filename);
+		assertThat(resource.getInputStream()).hasContent(body);
+	}
+
+	private DataBuffer stringBuffer(String value) {
+		byte[] bytes = value.getBytes(StandardCharsets.UTF_8);
+		DataBuffer buffer = this.bufferFactory.allocateBuffer(bytes.length);
+		buffer.write(bytes);
+		return buffer;
+	}
+
+}