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 abstract class AbstractGenericHttpMessageConverter<T> extends AbstractHtt
 		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 abstract class AbstractHttpMessageConverter<T> implements HttpMessageConv
 		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 @@ public abstract class AbstractHttpMessageConverter<T> implements HttpMessageConv
 		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 @@ public abstract class AbstractKotlinSerializationHttpMessageConverter<T extends
 		}
 		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 class BufferedImageHttpMessageConverter implements HttpMessageConverter<B
 		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 @@ public class ByteArrayHttpMessageConverter extends AbstractHttpMessageConverter<
 		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 @@ public class FormHttpMessageConverter implements HttpMessageConverter<MultiValue
 		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 @@ public class ObjectToStringHttpMessageConverter extends AbstractHttpMessageConve
 		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 @@ public class ResourceHttpMessageConverter extends AbstractHttpMessageConverter<R
 		}
 	}
 
+	@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.lang.reflect.Type;
 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 @@ public class ResourceRegionHttpMessageConverter extends AbstractGenericHttpMessa
 		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 @@ public class StringHttpMessageConverter extends AbstractHttpMessageConverter<Str
 		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 @@ public abstract class AbstractWireFeedHttpMessageConverter<T extends WireFeed>
 		}
 	}
 
+	@Override
+	protected boolean supportsRepeatableWrites(T t) {
+		return true;
+	}
 }

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

@@ -568,4 +568,8 @@ public abstract class AbstractJackson2HttpMessageConverter extends AbstractGener
 		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 @@ public class GsonHttpMessageConverter extends AbstractJsonHttpMessageConverter {
 		}
 	}
 
+	@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 @@ public class JsonbHttpMessageConverter extends AbstractJsonHttpMessageConverter
 		}
 	}
 
+	@Override
+	protected boolean supportsRepeatableWrites(Object o) {
+		return true;
+	}
 }

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

@@ -247,6 +247,10 @@ public class ProtobufHttpMessageConverter extends AbstractHttpMessageConverter<M
 		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 @@ public class Jaxb2RootElementHttpMessageConverter extends AbstractJaxb2HttpMessa
 		}
 	}
 
+	@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 @@ public class MarshallingHttpMessageConverter extends AbstractXmlHttpMessageConve
 		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 @@ public class SourceHttpMessageConverter<T extends Source> extends AbstractHttpMe
 		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 class ByteArrayHttpMessageConverterTests {
 		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);
+	}
+
 }

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

@@ -171,4 +171,19 @@ class StringHttpMessageConverterTests {
 		assertThat(headers.getAcceptCharset()).isEmpty();
 	}
 
+	@Test
+	public void repeatableWrites() throws IOException {
+		MockHttpOutputMessage outputMessage1 = new MockHttpOutputMessage();
+		String body = "Hello World";
+		assertThat(converter.supportsRepeatableWrites(body)).isTrue();
+
+		converter.write(body, TEXT_PLAIN_UTF_8, outputMessage1);
+		assertThat(outputMessage1.getBodyAsString()).isEqualTo(body);
+
+		MockHttpOutputMessage outputMessage2 = new MockHttpOutputMessage();
+		converter.write(body, TEXT_PLAIN_UTF_8, outputMessage2);
+		assertThat(outputMessage2.getBodyAsString()).isEqualTo(body);
+	}
+
+
 }

spring-web/src/test/java/org/springframework/http/converter/json/MappingJackson2HttpMessageConverterTests.java

@@ -580,6 +580,22 @@ public class MappingJackson2HttpMessageConverterTests {
 		assertThat(result2).contains("\"property\":\"Value2\"");
 	}
 
+	@Test
+	public void repeatableWrites() throws IOException {
+		MockHttpOutputMessage outputMessage1 = new MockHttpOutputMessage();
+		MyBean body = new MyBean();
+		body.setString("Foo");
+		converter.write(body, null, outputMessage1);
+		String result = outputMessage1.getBodyAsString(StandardCharsets.UTF_8);
+		assertThat(result).contains("\"string\":\"Foo\"");
+
+		MockHttpOutputMessage outputMessage2 = new MockHttpOutputMessage();
+		converter.write(body, null, outputMessage2);
+		result = outputMessage2.getBodyAsString(StandardCharsets.UTF_8);
+		assertThat(result).contains("\"string\":\"Foo\"");
+	}
+
+
 
 	interface MyInterface {
 

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

@@ -290,6 +290,7 @@ public class SourceHttpMessageConverterTests {
 		DOMSource domSource = new DOMSource(document);
 
 		MockHttpOutputMessage outputMessage = new MockHttpOutputMessage();
+		assertThat(converter.supportsRepeatableWrites(domSource)).isTrue();
 		converter.write(domSource, null, outputMessage);
 		assertThat(XmlContent.of(outputMessage.getBodyAsString(StandardCharsets.UTF_8)))
 				.isSimilarTo("<root>Hello World</root>");
@@ -305,6 +306,7 @@ public class SourceHttpMessageConverterTests {
 		SAXSource saxSource = new SAXSource(new InputSource(new StringReader(xml)));
 
 		MockHttpOutputMessage outputMessage = new MockHttpOutputMessage();
+		assertThat(converter.supportsRepeatableWrites(saxSource)).isFalse();
 		converter.write(saxSource, null, outputMessage);
 		assertThat(XmlContent.of(outputMessage.getBodyAsString(StandardCharsets.UTF_8)))
 				.isSimilarTo("<root>Hello World</root>");
@@ -318,6 +320,7 @@ public class SourceHttpMessageConverterTests {
 		StreamSource streamSource = new StreamSource(new StringReader(xml));
 
 		MockHttpOutputMessage outputMessage = new MockHttpOutputMessage();
+		assertThat(converter.supportsRepeatableWrites(streamSource)).isFalse();
 		converter.write(streamSource, null, outputMessage);
 		assertThat(XmlContent.of(outputMessage.getBodyAsString(StandardCharsets.UTF_8)))
 				.isSimilarTo("<root>Hello World</root>");