From 9042682b566ffd6dcdd1a646910b67bad52cb31d Mon Sep 17 00:00:00 2001
From: rstoyanchev <rossen.stoyanchev@broadcom.com>
Date: Fri, 13 Feb 2026 12:38:38 +0000
Subject: [PATCH] Optimal charset handling in AbstractHttpMessageConverter

Closes gh-36320
---
 .../http/converter/AbstractHttpMessageConverter.java         | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/spring-web/src/main/java/org/springframework/http/converter/AbstractHttpMessageConverter.java b/spring-web/src/main/java/org/springframework/http/converter/AbstractHttpMessageConverter.java
index 4559ea375e2..92eca8fb1fa 100644
--- a/spring-web/src/main/java/org/springframework/http/converter/AbstractHttpMessageConverter.java
+++ b/spring-web/src/main/java/org/springframework/http/converter/AbstractHttpMessageConverter.java
@@ -254,13 +254,14 @@ public abstract class AbstractHttpMessageConverter<T> implements HttpMessageConv
 				contentTypeToUse = (mediaType != null ? mediaType : contentTypeToUse);
 			}
 			if (contentTypeToUse != null) {
+				String value = contentTypeToUse.toString();
 				if (contentTypeToUse.getCharset() == null) {
 					Charset defaultCharset = getDefaultCharset();
 					if (defaultCharset != null) {
-						contentTypeToUse = new MediaType(contentTypeToUse, defaultCharset);
+						value += ";charset=" + defaultCharset.name();
 					}
 				}
-				headers.setContentType(contentTypeToUse);
+				headers.set(HttpHeaders.CONTENT_TYPE, value);
 			}
 		}
 		if (headers.getContentLength() < 0 && !headers.containsKey(HttpHeaders.TRANSFER_ENCODING)) {