ResourceDecoder supports filename hint

Closes gh-22267

spring-core/src/test/java/org/springframework/core/codec/ResourceDecoderTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2019 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.
@@ -18,6 +18,7 @@ package org.springframework.core.codec;
 
 import java.io.IOException;
 import java.nio.charset.StandardCharsets;
+import java.util.Collections;
 import java.util.Map;
 
 import org.junit.Test;
@@ -100,23 +101,28 @@ public class ResourceDecoderTests extends AbstractDecoderTestCase<ResourceDecode
 	}
 
 	@Override
-	public void decodeToMono() throws Exception {
+	public void decodeToMono() {
 		Flux<DataBuffer> input = Flux.concat(
 				dataBuffer(this.fooBytes),
 				dataBuffer(this.barBytes));
 
-		testDecodeToMonoAll(input, Resource.class, step -> step
-				.consumeNextWith(resource -> {
-					try {
-						byte[] bytes = StreamUtils.copyToByteArray(resource.getInputStream());
-						assertEquals("foobar", new String(bytes));
-					}
-					catch (IOException e) {
-						fail(e.getMessage());
-					}
-				})
-				.expectComplete()
-				.verify());
+		testDecodeToMonoAll(input, ResolvableType.forClass(Resource.class),
+				step -> step
+						.consumeNextWith(value -> {
+							Resource resource = (Resource) value;
+							try {
+								byte[] bytes = StreamUtils.copyToByteArray(resource.getInputStream());
+								assertEquals("foobar", new String(bytes));
+								assertEquals("testFile", resource.getFilename());
+							}
+							catch (IOException e) {
+								fail(e.getMessage());
+							}
+						})
+						.expectComplete()
+						.verify(),
+				null,
+				Collections.singletonMap(ResourceDecoder.FILENAME_HINT, "testFile"));
 	}
 
 }