Consistent adaptation of HTTP headers on Servlet responses

Closes gh-36345

spring-web/src/main/java/org/springframework/http/server/ServletServerHttpRequest.java

@@ -187,10 +187,10 @@ public class ServletServerHttpRequest implements ServerHttpRequest {
 				if (contentType != null && contentType.getCharset() == null) {
 					String requestEncoding = this.servletRequest.getCharacterEncoding();
 					if (StringUtils.hasLength(requestEncoding)) {
-						Charset charSet = Charset.forName(requestEncoding);
+						Charset charset = Charset.forName(requestEncoding);
 						Map<String, String> params = new LinkedCaseInsensitiveMap<>();
 						params.putAll(contentType.getParameters());
-						params.put("charset", charSet.toString());
+						params.put("charset", charset.toString());
 						MediaType mediaType = new MediaType(contentType.getType(), contentType.getSubtype(), params);
 						this.headers.setContentType(mediaType);
 					}
@@ -207,7 +207,6 @@ public class ServletServerHttpRequest implements ServerHttpRequest {
 				}
 			}
 		}
-
 		return this.headers;
 	}
 

spring-web/src/main/java/org/springframework/http/server/ServletServerHttpResponse.java

@@ -18,6 +18,7 @@ package org.springframework.http.server;
 
 import java.io.IOException;
 import java.io.OutputStream;
+import java.nio.charset.Charset;
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Collections;
@@ -118,19 +119,31 @@ public class ServletServerHttpResponse implements ServerHttpResponse {
 					this.servletResponse.addHeader(headerName, headerValue);
 				}
 			});
+
 			// HttpServletResponse exposes some headers as properties: we should include those if not already present
-			MediaType contentTypeHeader = this.headers.getContentType();
+			if (this.servletResponse.getContentType() == null && this.headers.containsKey(HttpHeaders.CONTENT_TYPE)) {
-			if (this.servletResponse.getContentType() == null && contentTypeHeader != null) {
+				this.servletResponse.setContentType(this.headers.getFirst(HttpHeaders.CONTENT_TYPE));
-				this.servletResponse.setContentType(contentTypeHeader.toString());
 			}
-			if (this.servletResponse.getCharacterEncoding() == null && contentTypeHeader != null &&
+			if (this.servletResponse.getCharacterEncoding() == null && this.headers.containsKey(HttpHeaders.CONTENT_TYPE)) {
-					contentTypeHeader.getCharset() != null) {
+				try {
-				this.servletResponse.setCharacterEncoding(contentTypeHeader.getCharset().name());
+					// Lazy parsing into MediaType
+					MediaType contentType = this.headers.getContentType();
+					if (contentType != null) {
+						Charset charset = contentType.getCharset();
+						if (charset != null) {
+							this.servletResponse.setCharacterEncoding(charset.name());
+						}
+					}
+				}
+				catch (Exception ex) {
+					// Leave character encoding unspecified
+				}
 			}
-			long contentLength = getHeaders().getContentLength();
+			long contentLength = this.headers.getContentLength();
 			if (contentLength != -1) {
 				this.servletResponse.setContentLengthLong(contentLength);
 			}
+
 			this.headersWritten = true;
 		}
 	}

spring-web/src/main/java/org/springframework/http/server/reactive/ServletServerHttpResponse.java

@@ -50,7 +50,9 @@ import org.springframework.util.ReflectionUtils;
  */
 class ServletServerHttpResponse extends AbstractListenerServerHttpResponse {
 
-	private static final boolean IS_SERVLET61 = ReflectionUtils.findField(HttpServletResponse.class, "SC_PERMANENT_REDIRECT") != null;
+	private static final boolean SERVLET61 =
+			(ReflectionUtils.findField(HttpServletResponse.class, "SC_PERMANENT_REDIRECT") != null);
+
 
 	private final HttpServletResponse response;
 
@@ -138,31 +140,35 @@ class ServletServerHttpResponse extends AbstractListenerServerHttpResponse {
 	}
 
 	protected void adaptHeaders(boolean removeAdaptedHeaders) {
-		MediaType contentType = null;
+		HttpHeaders headers = getHeaders();
-		try {
-			contentType = getHeaders().getContentType();
-		}
-		catch (Exception ex) {
-			String rawContentType = getHeaders().getFirst(HttpHeaders.CONTENT_TYPE);
-			this.response.setContentType(rawContentType);
-		}
-		if (this.response.getContentType() == null && contentType != null) {
-			this.response.setContentType(contentType.toString());
-		}
 
-		Charset charset = (contentType != null ? contentType.getCharset() : null);
+		// HttpServletResponse exposes some headers as properties: we should include those if not already present
-		if (this.response.getCharacterEncoding() == null && charset != null) {
+		if (this.response.getContentType() == null && headers.containsKey(HttpHeaders.CONTENT_TYPE)) {
-			this.response.setCharacterEncoding(charset.name());
+			this.response.setContentType(headers.getFirst(HttpHeaders.CONTENT_TYPE));
 		}
-
+		if (this.response.getCharacterEncoding() == null && headers.containsKey(HttpHeaders.CONTENT_TYPE)) {
-		long contentLength = getHeaders().getContentLength();
+			try {
+				// Lazy parsing into MediaType
+				MediaType contentType = headers.getContentType();
+				if (contentType != null) {
+					Charset charset = contentType.getCharset();
+					if (charset != null) {
+						this.response.setCharacterEncoding(charset.name());
+					}
+				}
+			}
+			catch (Exception ex) {
+				// Leave character encoding unspecified
+			}
+		}
+		long contentLength = headers.getContentLength();
 		if (contentLength != -1) {
 			this.response.setContentLengthLong(contentLength);
 		}
 
 		if (removeAdaptedHeaders) {
-			getHeaders().remove(HttpHeaders.CONTENT_TYPE);
+			headers.remove(HttpHeaders.CONTENT_TYPE);
-			getHeaders().remove(HttpHeaders.CONTENT_LENGTH);
+			headers.remove(HttpHeaders.CONTENT_LENGTH);
 		}
 	}
 
@@ -186,7 +192,7 @@ class ServletServerHttpResponse extends AbstractListenerServerHttpResponse {
 				cookie.setSecure(httpCookie.isSecure());
 				cookie.setHttpOnly(httpCookie.isHttpOnly());
 				if (httpCookie.isPartitioned()) {
-					if (IS_SERVLET61) {
+					if (SERVLET61) {
 						cookie.setAttribute("Partitioned", "");
 					}
 					else {
@@ -373,7 +379,6 @@ class ServletServerHttpResponse extends AbstractListenerServerHttpResponse {
 
 	private class ResponseBodyProcessor extends AbstractListenerWriteProcessor<DataBuffer> {
 
-
 		public ResponseBodyProcessor() {
 			super(request.getLogPrefix());
 		}

spring-webmvc/src/main/java/org/springframework/web/servlet/function/AbstractServerResponse.java

@@ -17,6 +17,7 @@
 package org.springframework.web.servlet.function;
 
 import java.io.IOException;
+import java.nio.charset.Charset;
 import java.util.Collection;
 import java.util.Set;
 
@@ -28,6 +29,7 @@ import jakarta.servlet.http.HttpServletResponse;
 import org.springframework.http.HttpHeaders;
 import org.springframework.http.HttpMethod;
 import org.springframework.http.HttpStatusCode;
+import org.springframework.http.MediaType;
 import org.springframework.lang.Nullable;
 import org.springframework.util.CollectionUtils;
 import org.springframework.util.LinkedMultiValueMap;
@@ -51,6 +53,7 @@ abstract class AbstractServerResponse extends ErrorHandlingServerResponse {
 
 	private final MultiValueMap<String, Cookie> cookies;
 
+
 	protected AbstractServerResponse(
 			HttpStatusCode statusCode, HttpHeaders headers, MultiValueMap<String, Cookie> cookies) {
 
@@ -60,6 +63,7 @@ abstract class AbstractServerResponse extends ErrorHandlingServerResponse {
 				CollectionUtils.unmodifiableMultiValueMap(new LinkedMultiValueMap<>(cookies));
 	}
 
+
 	@Override
 	public final HttpStatusCode statusCode() {
 		return this.statusCode;
@@ -118,14 +122,29 @@ abstract class AbstractServerResponse extends ErrorHandlingServerResponse {
 				servletResponse.addHeader(headerName, headerValue);
 			}
 		});
+
 		// HttpServletResponse exposes some headers as properties: we should include those if not already present
-		if (servletResponse.getContentType() == null && this.headers.getContentType() != null) {
+		if (servletResponse.getContentType() == null && this.headers.containsKey(HttpHeaders.CONTENT_TYPE)) {
-			servletResponse.setContentType(this.headers.getContentType().toString());
+			servletResponse.setContentType(this.headers.getFirst(HttpHeaders.CONTENT_TYPE));
 		}
-		if (servletResponse.getCharacterEncoding() == null &&
+		if (servletResponse.getCharacterEncoding() == null && this.headers.containsKey(HttpHeaders.CONTENT_TYPE)) {
-				this.headers.getContentType() != null &&
+			try {
-				this.headers.getContentType().getCharset() != null) {
+				// Lazy parsing into MediaType
-			servletResponse.setCharacterEncoding(this.headers.getContentType().getCharset().name());
+				MediaType contentType = this.headers.getContentType();
+				if (contentType != null) {
+					Charset charset = contentType.getCharset();
+					if (charset != null) {
+						servletResponse.setCharacterEncoding(charset.name());
+					}
+				}
+			}
+			catch (Exception ex) {
+				// Leave character encoding unspecified
+			}
+		}
+		long contentLength = this.headers.getContentLength();
+		if (contentLength != -1) {
+			servletResponse.setContentLengthLong(contentLength);
 		}
 	}
 

spring-webmvc/src/main/java/org/springframework/web/servlet/mvc/method/annotation/ResponseBodyEmitterReturnValueHandler.java

@@ -459,6 +459,11 @@ public class ResponseBodyEmitterReturnValueHandler implements HandlerMethodRetur
 			// ignore
 		}
 
+		// @Override - on Servlet 6.1
+		public void setCharacterEncoding(Charset encoding) {
+			// ignore
+		}
+
 		@Override
 		public void setContentLength(int len) {
 			// ignore