Clean HTTP response headers after decompression in JDK client

Prior to this commit, gh-35225 introduced HTTP response body
decompression support for "gzip" and "deflate" encodings for the
`JdkClientHttpRequestFactory`.

While body decompression works, the client keeps the "Content-Encoding"
and "Content-Length" response headers intact, which misleads further
response handling: the body size has changed and it is not compressed
anymore.

This commit ensures that the relevant response headers are removed from
the HTTP response after decompression.

Fixes gh-35668

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

@@ -43,6 +43,7 @@ import java.util.concurrent.Executor;
 import java.util.concurrent.Flow;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.function.Consumer;
 import java.util.zip.GZIPInputStream;
 import java.util.zip.InflaterInputStream;
 
@@ -113,16 +114,15 @@ class JdkClientHttpRequest extends AbstractStreamingClientHttpRequest {
 		try {
 			HttpRequest request = buildRequest(headers, body);
 			responseFuture = this.httpClient.sendAsync(request, this.compression ? new DecompressingBodyHandler() : HttpResponse.BodyHandlers.ofInputStream());
-
 			if (this.timeout != null) {
 				timeoutHandler = new TimeoutHandler(responseFuture, this.timeout);
 				HttpResponse<InputStream> response = responseFuture.get();
 				InputStream inputStream = timeoutHandler.wrapInputStream(response);
-				return new JdkClientHttpResponse(response, inputStream);
+				return new JdkClientHttpResponse(response, processResponseHeaders(), inputStream);
 			}
 			else {
 				HttpResponse<InputStream> response = responseFuture.get();
-				return new JdkClientHttpResponse(response, response.body());
+				return new JdkClientHttpResponse(response, processResponseHeaders(), response.body());
 			}
 		}
 		catch (InterruptedException ex) {
@@ -231,6 +231,19 @@ class JdkClientHttpRequest extends AbstractStreamingClientHttpRequest {
 		return Collections.unmodifiableSet(headers);
 	}
 
+	private Consumer<HttpHeaders> processResponseHeaders() {
+		if (this.compression) {
+			return headers -> {
+				String encoding = headers.getFirst(HttpHeaders.CONTENT_ENCODING);
+				if (encoding != null && SUPPORTED_ENCODINGS.contains(encoding)) {
+					headers.remove(HttpHeaders.CONTENT_ENCODING);
+					headers.remove(HttpHeaders.CONTENT_LENGTH);
+				}
+			};
+		}
+		return headers -> {};
+	}
+
 
 	private static final class ByteBufferMapper implements OutputStreamPublisher.ByteMapper<ByteBuffer> {
 

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

@@ -21,17 +21,14 @@ import java.io.InputStream;
 import java.net.http.HttpClient;
 import java.net.http.HttpResponse;
 import java.util.List;
-import java.util.Locale;
 import java.util.Map;
+import java.util.function.Consumer;
 
 import org.jspecify.annotations.Nullable;
 
 import org.springframework.http.HttpHeaders;
 import org.springframework.http.HttpStatus;
 import org.springframework.http.HttpStatusCode;
-import org.springframework.util.CollectionUtils;
-import org.springframework.util.LinkedCaseInsensitiveMap;
-import org.springframework.util.MultiValueMap;
 import org.springframework.util.StreamUtils;
 
 /**
@@ -50,18 +47,18 @@ class JdkClientHttpResponse implements ClientHttpResponse {
 	private final InputStream body;
 
 
-	public JdkClientHttpResponse(HttpResponse<InputStream> response, @Nullable InputStream body) {
+	JdkClientHttpResponse(HttpResponse<InputStream> response, Consumer<HttpHeaders> headersConsumer, @Nullable InputStream body) {
 		this.response = response;
-		this.headers = adaptHeaders(response);
+		this.headers = adaptHeaders(response, headersConsumer);
 		this.body = (body != null ? body : InputStream.nullInputStream());
 	}
 
-	private static HttpHeaders adaptHeaders(HttpResponse<?> response) {
+	private static HttpHeaders adaptHeaders(HttpResponse<?> response, Consumer<HttpHeaders> headersConsumer) {
 		Map<String, List<String>> rawHeaders = response.headers().map();
-		Map<String, List<String>> map = new LinkedCaseInsensitiveMap<>(rawHeaders.size(), Locale.ROOT);
-		MultiValueMap<String, String> multiValueMap = CollectionUtils.toMultiValueMap(map);
-		multiValueMap.putAll(rawHeaders);
-		return HttpHeaders.readOnlyHttpHeaders(multiValueMap);
+		HttpHeaders headers = new HttpHeaders();
+		rawHeaders.forEach(headers::put);
+		headersConsumer.accept(headers);
+		return HttpHeaders.readOnlyHttpHeaders(headers);
 	}