Add setBody with byte[] to StreamingHttpOutputMessage

Sometimes the content to write is already buffered, but requires boilerplate
to write through a Body callback.

See gh-33785

spring-web/src/main/java/org/springframework/http/StreamingHttpOutputMessage.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2023 the original author or authors.
+ * Copyright 2002-2025 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.
@@ -19,6 +19,8 @@ package org.springframework.http;
 import java.io.IOException;
 import java.io.OutputStream;
 
+import org.springframework.util.StreamUtils;
+
 /**
  * Represents an HTTP output message that allows for setting a streaming body.
  * Note that such messages typically do not support {@link #getBody()} access.
@@ -35,6 +37,27 @@ public interface StreamingHttpOutputMessage extends HttpOutputMessage {
 	 */
 	void setBody(Body body);
 
+	/**
+	 * Variant of {@link #setBody(Body)} for a non-streaming write.
+	 * @param body the content to write
+	 * @throws IOException if an I/O exception occurs
+	 * @since 7.0
+	 */
+	default void setBody(byte[] body) throws IOException {
+		setBody(new Body() {
+			@Override
+			public void writeTo(OutputStream outputStream) throws IOException {
+				StreamUtils.copy(body, outputStream);
+			}
+
+			@Override
+			public boolean repeatable() {
+				return true;
+			}
+		});
+	}
+
+
 
 	/**
 	 * Defines the contract for bodies that can be written directly to an

spring-web/src/main/java/org/springframework/http/client/AbstractBufferingClientHttpRequest.java

@@ -64,35 +64,25 @@ abstract class AbstractBufferingClientHttpRequest extends AbstractClientHttpRequ
 	/**
 	 * Execute with the given request and body.
 	 * @param request the request to execute with
-	 * @param body the body to send
+	 * @param bufferedOutput the body to write
 	 * @param bufferResponse whether to buffer the response
 	 * @return the resulting response
 	 * @throws IOException in case of I/O errors from execution
 	 * @since 7.0
 	 */
 	protected ClientHttpResponse executeWithRequest(
-			ClientHttpRequest request, byte[] body, boolean bufferResponse) throws IOException {
+			ClientHttpRequest request, byte[] bufferedOutput, boolean bufferResponse) throws IOException {
 
-		if (body.length > 0) {
+		if (bufferedOutput.length > 0) {
 			long contentLength = request.getHeaders().getContentLength();
-			if (contentLength > -1 && contentLength != body.length) {
+			if (contentLength > -1 && contentLength != bufferedOutput.length) {
-				request.getHeaders().setContentLength(body.length);
+				request.getHeaders().setContentLength(bufferedOutput.length);
 			}
 			if (request instanceof StreamingHttpOutputMessage streamingOutputMessage) {
-				streamingOutputMessage.setBody(new StreamingHttpOutputMessage.Body() {
+				streamingOutputMessage.setBody(bufferedOutput);
-					@Override
-					public void writeTo(OutputStream outputStream) throws IOException {
-						StreamUtils.copy(body, outputStream);
-					}
-
-					@Override
-					public boolean repeatable() {
-						return true;
-					}
-				});
 			}
 			else {
-				StreamUtils.copy(body, request.getBody());
+				StreamUtils.copy(bufferedOutput, request.getBody());
 			}
 		}
 

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2024 the original author or authors.
+ * Copyright 2002-2025 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.
@@ -404,17 +404,7 @@ public class FormHttpMessageConverter implements HttpMessageConverter<MultiValue
 		outputMessage.getHeaders().setContentLength(bytes.length);
 
 		if (outputMessage instanceof StreamingHttpOutputMessage streamingOutputMessage) {
-			streamingOutputMessage.setBody(new StreamingHttpOutputMessage.Body() {
+			streamingOutputMessage.setBody(bytes);
-				@Override
-				public void writeTo(OutputStream outputStream) throws IOException {
-					StreamUtils.copy(bytes, outputStream);
-				}
-
-				@Override
-				public boolean repeatable() {
-					return true;
-				}
-			});
 		}
 		else {
 			StreamUtils.copy(bytes, outputMessage.getBody());