Support filename hint for client side too

Closes gh-25516

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;
+	}
+
+}