From adffb9a494b5871d84e4143cd0638c39482e9f2f Mon Sep 17 00:00:00 2001
From: config25 <yhkim052556@naver.com>
Date: Wed, 8 Apr 2026 09:07:18 +0900
Subject: [PATCH] Fix URL decoding charset mismatch in MockMvcRequestConverter

Signed-off-by: config25 <yhkim052556@naver.com>

See gh-1034
---
 .../restdocs/mockmvc/MockMvcRequestConverter.java     |  2 +-
 .../mockmvc/MockMvcRequestConverterTests.java         | 11 +++++++++++
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/spring-restdocs-mockmvc/src/main/java/org/springframework/restdocs/mockmvc/MockMvcRequestConverter.java b/spring-restdocs-mockmvc/src/main/java/org/springframework/restdocs/mockmvc/MockMvcRequestConverter.java
index dd0c03c2..8ebd1a12 100644
--- a/spring-restdocs-mockmvc/src/main/java/org/springframework/restdocs/mockmvc/MockMvcRequestConverter.java
+++ b/spring-restdocs-mockmvc/src/main/java/org/springframework/restdocs/mockmvc/MockMvcRequestConverter.java
@@ -280,7 +280,7 @@ private static void processParameter(String parameter, MultiValueMap<String, Str
 	}
 
 	private static String decode(String encoded) {
-		return URLDecoder.decode(encoded, StandardCharsets.US_ASCII);
+		return URLDecoder.decode(encoded, StandardCharsets.UTF_8);
 	}
 
 }
diff --git a/spring-restdocs-mockmvc/src/test/java/org/springframework/restdocs/mockmvc/MockMvcRequestConverterTests.java b/spring-restdocs-mockmvc/src/test/java/org/springframework/restdocs/mockmvc/MockMvcRequestConverterTests.java
index 66af0e11..9ed5c969 100644
--- a/spring-restdocs-mockmvc/src/test/java/org/springframework/restdocs/mockmvc/MockMvcRequestConverterTests.java
+++ b/spring-restdocs-mockmvc/src/test/java/org/springframework/restdocs/mockmvc/MockMvcRequestConverterTests.java
@@ -158,6 +158,17 @@ public void postRequestWithParametersAndQueryStringCreatesFormUrlEncodedContentW
 		assertThat(request.getHeaders().getContentType()).isEqualTo(MediaType.APPLICATION_FORM_URLENCODED);
 	}
 
+	@Test
+	public void postRequestWithNonAsciiParametersAndQueryStringCreatesFormUrlEncodedContentWithoutDuplication() {
+		OperationRequest request = createOperationRequest(MockMvcRequestBuilders.post("/foo?name=\uD64D\uAE38\uB3D9")
+			.param("name", "\uD64D\uAE38\uB3D9")
+			.param("other", "\uD64D\uAE38\uB3D9"));
+		assertThat(request.getUri()).isEqualTo(URI.create("http://localhost/foo?name=%ED%99%8D%EA%B8%B8%EB%8F%99"));
+		assertThat(request.getMethod()).isEqualTo(HttpMethod.POST);
+		assertThat(request.getContentAsString()).isEqualTo("other=%ED%99%8D%EA%B8%B8%EB%8F%99");
+		assertThat(request.getHeaders().getContentType()).isEqualTo(MediaType.APPLICATION_FORM_URLENCODED);
+	}
+
 	@Test
 	public void mockMultipartFileUpload() {
 		OperationRequest request = createOperationRequest(MockMvcRequestBuilders.multipart("/foo")