From e96b71acf3af4df7d00270e93659ec1f00495fdc Mon Sep 17 00:00:00 2001
From: Oleh Faizulin <oleh.faizulin@gmail.com>
Date: Sat, 4 Jan 2020 09:54:53 +0200
Subject: [PATCH] contentLength support for Resource decoding

Expose the known content length, if known, in the InputStreamResource returned by ResourceHttpMessageConverter or
ResourceDecoder.

See gh-24292
---
 .../core/codec/ResourceDecoder.java            |  5 +++++
 .../core/codec/ResourceDecoderTests.java       | 18 ++++++++++++++++++
 .../ResourceHttpMessageConverter.java          |  5 +++++
 .../ResourceHttpMessageConverterTests.java     |  2 ++
 4 files changed, 30 insertions(+)

diff --git a/spring-core/src/main/java/org/springframework/core/codec/ResourceDecoder.java b/spring-core/src/main/java/org/springframework/core/codec/ResourceDecoder.java
index eeb307cfcd..b19e6f9545 100644
--- a/spring-core/src/main/java/org/springframework/core/codec/ResourceDecoder.java
+++ b/spring-core/src/main/java/org/springframework/core/codec/ResourceDecoder.java
@@ -83,6 +83,11 @@ public class ResourceDecoder extends AbstractDataBufferDecoder<Resource> {
 				public String getFilename() {
 					return filename;
 				}
+
+				@Override
+				public long contentLength() {
+					return bytes.length;
+				}
 			};
 		}
 		else if (Resource.class.isAssignableFrom(clazz)) {
diff --git a/spring-core/src/test/java/org/springframework/core/codec/ResourceDecoderTests.java b/spring-core/src/test/java/org/springframework/core/codec/ResourceDecoderTests.java
index 1c3a531f7a..3c129428f5 100644
--- a/spring-core/src/test/java/org/springframework/core/codec/ResourceDecoderTests.java
+++ b/spring-core/src/test/java/org/springframework/core/codec/ResourceDecoderTests.java
@@ -105,4 +105,22 @@ class ResourceDecoderTests extends AbstractDecoderTests<ResourceDecoder> {
 				Collections.singletonMap(ResourceDecoder.FILENAME_HINT, "testFile"));
 	}
 
+	@Test
+	public void decodeInputStreamResource() {
+		Flux<DataBuffer> input = Flux.concat(dataBuffer(this.fooBytes), dataBuffer(this.barBytes));
+		testDecodeAll(input, InputStreamResource.class, step -> step
+				.consumeNextWith(resource -> {
+					try {
+						byte[] bytes = StreamUtils.copyToByteArray(resource.getInputStream());
+						assertThat(new String(bytes)).isEqualTo("foobar");
+						assertThat(resource.contentLength()).isEqualTo(fooBytes.length + barBytes.length);
+					}
+					catch (IOException ex) {
+						throw new AssertionError(ex.getMessage(), ex);
+					}
+				})
+				.expectComplete()
+				.verify());
+	}
+
 }
diff --git a/spring-web/src/main/java/org/springframework/http/converter/ResourceHttpMessageConverter.java b/spring-web/src/main/java/org/springframework/http/converter/ResourceHttpMessageConverter.java
index 582ab859de..3fd7208315 100644
--- a/spring-web/src/main/java/org/springframework/http/converter/ResourceHttpMessageConverter.java
+++ b/spring-web/src/main/java/org/springframework/http/converter/ResourceHttpMessageConverter.java
@@ -84,6 +84,11 @@ public class ResourceHttpMessageConverter extends AbstractHttpMessageConverter<R
 				public String getFilename() {
 					return inputMessage.getHeaders().getContentDisposition().getFilename();
 				}
+
+				@Override
+				public long contentLength() {
+					return inputMessage.getHeaders().getContentLength();
+				}
 			};
 		}
 		else if (Resource.class == clazz || ByteArrayResource.class.isAssignableFrom(clazz)) {
diff --git a/spring-web/src/test/java/org/springframework/http/converter/ResourceHttpMessageConverterTests.java b/spring-web/src/test/java/org/springframework/http/converter/ResourceHttpMessageConverterTests.java
index efc1163bd7..082ec788ca 100644
--- a/spring-web/src/test/java/org/springframework/http/converter/ResourceHttpMessageConverterTests.java
+++ b/spring-web/src/test/java/org/springframework/http/converter/ResourceHttpMessageConverterTests.java
@@ -80,10 +80,12 @@ public class ResourceHttpMessageConverterTests {
 			inputMessage.getHeaders().setContentType(MediaType.IMAGE_JPEG);
 			inputMessage.getHeaders().setContentDisposition(
 					ContentDisposition.builder("attachment").filename("yourlogo.jpg").build());
+			inputMessage.getHeaders().setContentLength(123);
 			Resource actualResource = converter.read(InputStreamResource.class, inputMessage);
 			assertThat(actualResource).isInstanceOf(InputStreamResource.class);
 			assertThat(actualResource.getInputStream()).isEqualTo(body);
 			assertThat(actualResource.getFilename()).isEqualTo("yourlogo.jpg");
+			assertThat(actualResource.contentLength()).isEqualTo(123);
 		}
 	}