Allow repeatable writes in HttpMessageConverter

This commit ensures that the StreamingHttpOutputMessage.Body.repeatable
flag is set in message converters for bodies that can be written
repeatedly.

Closes gh-31516
See gh-31449

spring-web/src/main/java/org/springframework/http/converter/AbstractGenericHttpMessageConverter.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2021 the original author or authors.
+ * Copyright 2002-2023 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.
@@ -88,16 +88,27 @@ public final void write(final T t, @Nullable final Type type, @Nullable MediaTyp
 		addDefaultHeaders(headers, t, contentType);
 
 		if (outputMessage instanceof StreamingHttpOutputMessage streamingOutputMessage) {
-			streamingOutputMessage.setBody(outputStream -> writeInternal(t, type, new HttpOutputMessage() {
+			streamingOutputMessage.setBody(new StreamingHttpOutputMessage.Body() {
 				@Override
-				public OutputStream getBody() {
-					return outputStream;
+				public void writeTo(OutputStream outputStream) throws IOException {
+					writeInternal(t, type, new HttpOutputMessage() {
+						@Override
+						public OutputStream getBody() {
+							return outputStream;
+						}
+
+						@Override
+						public HttpHeaders getHeaders() {
+							return headers;
+						}
+					});
 				}
+
 				@Override
-				public HttpHeaders getHeaders() {
-					return headers;
+				public boolean repeatable() {
+					return supportsRepeatableWrites(t);
 				}
-			}));
+			});
 		}
 		else {
 			writeInternal(t, type, outputMessage);

spring-web/src/main/java/org/springframework/http/converter/AbstractHttpMessageConverter.java

@@ -210,16 +210,27 @@ public final void write(final T t, @Nullable MediaType contentType, HttpOutputMe
 		addDefaultHeaders(headers, t, contentType);
 
 		if (outputMessage instanceof StreamingHttpOutputMessage streamingOutputMessage) {
-			streamingOutputMessage.setBody(outputStream -> writeInternal(t, new HttpOutputMessage() {
+			streamingOutputMessage.setBody(new StreamingHttpOutputMessage.Body() {
 				@Override
-				public OutputStream getBody() {
-					return outputStream;
+				public void writeTo(OutputStream outputStream) throws IOException {
+					writeInternal(t, new HttpOutputMessage() {
+						@Override
+						public OutputStream getBody() {
+							return outputStream;
+						}
+
+						@Override
+						public HttpHeaders getHeaders() {
+							return headers;
+						}
+					});
 				}
+
 				@Override
-				public HttpHeaders getHeaders() {
-					return headers;
+				public boolean repeatable() {
+					return supportsRepeatableWrites(t);
 				}
-			}));
+			});
 		}
 		else {
 			writeInternal(t, outputMessage);
@@ -289,6 +300,21 @@ protected Long getContentLength(T t, @Nullable MediaType contentType) throws IOE
 		return null;
 	}
 
+	/**
+	 * Indicates whether this message converter can
+	 * {@linkplain #write(Object, MediaType, HttpOutputMessage) write} the
+	 * given object multiple times.
+	 *
+	 * <p>Default implementation returns {@code false}.
+	 * @param t the object t
+	 * @return {@code true} if {@code t} can be written repeatedly;
+	 * {@code false} otherwise
+	 * @since 6.1
+	 */
+	protected boolean supportsRepeatableWrites(T t) {
+		return false;
+	}
+
 
 	/**
 	 * Indicates whether the given class is supported by this converter.

spring-web/src/main/java/org/springframework/http/converter/AbstractKotlinSerializationHttpMessageConverter.java

@@ -178,4 +178,9 @@ private boolean hasPolymorphism(SerialDescriptor descriptor, Set<String> already
 		}
 		return false;
 	}
+
+	@Override
+	protected boolean supportsRepeatableWrites(Object object) {
+		return true;
+	}
 }

spring-web/src/main/java/org/springframework/http/converter/BufferedImageHttpMessageConverter.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2022 the original author or authors.
+ * Copyright 2002-2023 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.
@@ -226,7 +226,17 @@ public void write(final BufferedImage image, @Nullable final MediaType contentTy
 		outputMessage.getHeaders().setContentType(selectedContentType);
 
 		if (outputMessage instanceof StreamingHttpOutputMessage streamingOutputMessage) {
-			streamingOutputMessage.setBody(outputStream -> writeInternal(image, selectedContentType, outputStream));
+			streamingOutputMessage.setBody(new StreamingHttpOutputMessage.Body() {
+				@Override
+				public void writeTo(OutputStream outputStream) throws IOException {
+					BufferedImageHttpMessageConverter.this.writeInternal(image, selectedContentType, outputStream);
+				}
+
+				@Override
+				public boolean repeatable() {
+					return true;
+				}
+			});
 		}
 		else {
 			writeInternal(image, selectedContentType, outputMessage.getBody());

spring-web/src/main/java/org/springframework/http/converter/ByteArrayHttpMessageConverter.java

@@ -67,4 +67,8 @@ protected void writeInternal(byte[] bytes, HttpOutputMessage outputMessage) thro
 		StreamUtils.copy(bytes, outputMessage.getBody());
 	}
 
+	@Override
+	protected boolean supportsRepeatableWrites(byte[] bytes) {
+		return true;
+	}
 }

spring-web/src/main/java/org/springframework/http/converter/FormHttpMessageConverter.java

@@ -400,7 +400,17 @@ private void writeForm(MultiValueMap<String, Object> formData, @Nullable MediaTy
 		outputMessage.getHeaders().setContentLength(bytes.length);
 
 		if (outputMessage instanceof StreamingHttpOutputMessage streamingOutputMessage) {
-			streamingOutputMessage.setBody(outputStream -> StreamUtils.copy(bytes, outputStream));
+			streamingOutputMessage.setBody(new StreamingHttpOutputMessage.Body() {
+				@Override
+				public void writeTo(OutputStream outputStream) throws IOException {
+					StreamUtils.copy(bytes, outputStream);
+				}
+
+				@Override
+				public boolean repeatable() {
+					return true;
+				}
+			});
 		}
 		else {
 			StreamUtils.copy(bytes, outputMessage.getBody());

spring-web/src/main/java/org/springframework/http/converter/ObjectToStringHttpMessageConverter.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2023 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.
@@ -135,4 +135,8 @@ protected Long getContentLength(Object obj, @Nullable MediaType contentType) {
 		return this.stringHttpMessageConverter.getContentLength(value, contentType);
 	}
 
+	@Override
+	protected boolean supportsRepeatableWrites(Object o) {
+		return true;
+	}
 }

spring-web/src/main/java/org/springframework/http/converter/ResourceHttpMessageConverter.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2022 the original author or authors.
+ * Copyright 2002-2023 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.
@@ -166,4 +166,8 @@ protected void writeContent(Resource resource, HttpOutputMessage outputMessage)
 		}
 	}
 
+	@Override
+	protected boolean supportsRepeatableWrites(Resource resource) {
+		return !(resource instanceof InputStreamResource);
+	}
 }

spring-web/src/main/java/org/springframework/http/converter/ResourceRegionHttpMessageConverter.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2022 the original author or authors.
+ * Copyright 2002-2023 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.
@@ -24,6 +24,7 @@
 import java.nio.charset.StandardCharsets;
 import java.util.Collection;
 
+import org.springframework.core.io.InputStreamResource;
 import org.springframework.core.io.Resource;
 import org.springframework.core.io.support.ResourceRegion;
 import org.springframework.http.HttpHeaders;
@@ -238,4 +239,24 @@ private static void print(OutputStream os, String buf) throws IOException {
 		os.write(buf.getBytes(StandardCharsets.US_ASCII));
 	}
 
+	@Override
+	@SuppressWarnings("unchecked")
+	protected boolean supportsRepeatableWrites(Object object) {
+		if (object instanceof ResourceRegion resourceRegion) {
+			return supportsRepeatableWrites(resourceRegion);
+		}
+		else {
+			Collection<ResourceRegion> regions = (Collection<ResourceRegion>) object;
+			for (ResourceRegion region : regions) {
+				if (!supportsRepeatableWrites(region)) {
+					return false;
+				}
+			}
+			return true;
+		}
+	}
+
+	private boolean supportsRepeatableWrites(ResourceRegion region) {
+		return !(region.getResource() instanceof InputStreamResource);
+	}
 }

spring-web/src/main/java/org/springframework/http/converter/StringHttpMessageConverter.java

@@ -163,4 +163,8 @@ else if (contentType.isCompatibleWith(MediaType.APPLICATION_JSON) ||
 		return charset;
 	}
 
+	@Override
+	protected boolean supportsRepeatableWrites(String s) {
+		return true;
+	}
 }

spring-web/src/main/java/org/springframework/http/converter/feed/AbstractWireFeedHttpMessageConverter.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2022 the original author or authors.
+ * Copyright 2002-2023 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.
@@ -107,4 +107,8 @@ protected void writeInternal(T wireFeed, HttpOutputMessage outputMessage)
 		}
 	}
 
+	@Override
+	protected boolean supportsRepeatableWrites(T t) {
+		return true;
+	}
 }

spring-web/src/main/java/org/springframework/http/converter/json/AbstractJackson2HttpMessageConverter.java

@@ -568,4 +568,8 @@ protected Long getContentLength(Object object, @Nullable MediaType contentType)
 		return super.getContentLength(object, contentType);
 	}
 
+	@Override
+	protected boolean supportsRepeatableWrites(Object o) {
+		return true;
+	}
 }

spring-web/src/main/java/org/springframework/http/converter/json/GsonHttpMessageConverter.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2020 the original author or authors.
+ * Copyright 2002-2023 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.
@@ -107,4 +107,8 @@ protected void writeInternal(Object object, @Nullable Type type, Writer writer)
 		}
 	}
 
+	@Override
+	protected boolean supportsRepeatableWrites(Object o) {
+		return true;
+	}
 }

spring-web/src/main/java/org/springframework/http/converter/json/JsonbHttpMessageConverter.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2022 the original author or authors.
+ * Copyright 2002-2023 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.
@@ -110,4 +110,8 @@ protected void writeInternal(Object object, @Nullable Type type, Writer writer)
 		}
 	}
 
+	@Override
+	protected boolean supportsRepeatableWrites(Object o) {
+		return true;
+	}
 }

spring-web/src/main/java/org/springframework/http/converter/protobuf/ProtobufHttpMessageConverter.java

@@ -247,6 +247,10 @@ private void setProtoHeader(HttpOutputMessage response, Message message) {
 		response.getHeaders().set(X_PROTOBUF_MESSAGE_HEADER, message.getDescriptorForType().getFullName());
 	}
 
+	@Override
+	protected boolean supportsRepeatableWrites(Message message) {
+		return true;
+	}
 
 	/**
 	 * Protobuf format support.

spring-web/src/main/java/org/springframework/http/converter/xml/Jaxb2RootElementHttpMessageConverter.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2021 the original author or authors.
+ * Copyright 2002-2023 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.
@@ -200,6 +200,11 @@ private void setCharset(@Nullable MediaType contentType, Marshaller marshaller)
 		}
 	}
 
+	@Override
+	protected boolean supportsRepeatableWrites(Object o) {
+		return true;
+	}
+
 
 	private static final EntityResolver NO_OP_ENTITY_RESOLVER =
 			(publicId, systemId) -> new InputSource(new StringReader(""));

spring-web/src/main/java/org/springframework/http/converter/xml/MarshallingHttpMessageConverter.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2022 the original author or authors.
+ * Copyright 2002-2023 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.
@@ -137,4 +137,8 @@ protected void writeToResult(Object o, HttpHeaders headers, Result result) throw
 		this.marshaller.marshal(o, result);
 	}
 
+	@Override
+	protected boolean supportsRepeatableWrites(Object o) {
+		return true;
+	}
 }

spring-web/src/main/java/org/springframework/http/converter/xml/SourceHttpMessageConverter.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2022 the original author or authors.
+ * Copyright 2002-2023 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.
@@ -269,6 +269,11 @@ private void transform(Source source, Result result) throws TransformerException
 		this.transformerFactory.newTransformer().transform(source, result);
 	}
 
+	@Override
+	protected boolean supportsRepeatableWrites(T t) {
+		return t instanceof DOMSource;
+	}
+
 
 	private static class CountingOutputStream extends OutputStream {
 

spring-web/src/test/java/org/springframework/http/converter/ByteArrayHttpMessageConverterTests.java

@@ -79,4 +79,18 @@ public void write() throws IOException {
 		assertThat(outputMessage.getHeaders().getContentLength()).isEqualTo(2);
 	}
 
+	@Test
+	public void repeatableWrites() throws IOException {
+		MockHttpOutputMessage outputMessage1 = new MockHttpOutputMessage();
+		byte[] body = new byte[]{0x1, 0x2};
+		assertThat(converter.supportsRepeatableWrites(body)).isTrue();
+
+		converter.write(body, null, outputMessage1);
+		assertThat(outputMessage1.getBodyAsBytes()).isEqualTo(body);
+
+		MockHttpOutputMessage outputMessage2 = new MockHttpOutputMessage();
+		converter.write(body, null, outputMessage2);
+		assertThat(outputMessage2.getBodyAsBytes()).isEqualTo(body);
+	}
+
 }