fixHttpHeadersCasingForFabric (#46736)

* useLowerCaseResponseHeaders

---------

Co-authored-by: annie-mac <[email protected]>

Author: xinlian12

sdk/cosmos/azure-cosmos-tests/src/test/java/com/azure/cosmos/implementation/http/HttpHeadersTests.java

@@ -0,0 +1,29 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT License.
+
+package com.azure.cosmos.implementation.http;
+
+import org.testng.annotations.Test;
+
+import java.util.Map;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class HttpHeadersTests {
+
+    @Test(groups = "unit")
+    public void caseInsensitiveToMap() {
+        String headerName = "Etag";
+        String headerValue = "123";
+
+        HttpHeaders headers = new HttpHeaders();
+        headers.set(headerName, headerValue);
+
+        Map<String, String> lowerCaseMap = headers.toLowerCaseMap();
+        assertThat(lowerCaseMap.get(headerName.toLowerCase())).isEqualTo(headerValue);
+
+        Map<String, String> caseSensitiveMap = headers.toMap();
+        assertThat(caseSensitiveMap.get(headerName.toLowerCase())).isNull();
+        assertThat(caseSensitiveMap.get(headerName)).isEqualTo(headerValue);
+    }
+}

sdk/cosmos/azure-cosmos/CHANGELOG.md

@@ -10,6 +10,7 @@
 
 #### Other Changes
 * Changed to use `PartitionKeyRangeCache` to get partition key range during startup and split handling. - [46700](https://github.com/Azure/azure-sdk-for-java/pull/46700)
+* Changed to use lower casing http header names for gateway response. - [46736](https://github.com/Azure/azure-sdk-for-java/pull/46736)
 
 ### 4.74.0 (2025-09-05)
 

sdk/cosmos/azure-cosmos/src/main/java/com/azure/cosmos/implementation/RxGatewayStoreModel.java

@@ -220,7 +220,7 @@ public StoreResponse unwrapToStoreResponse(
             return new StoreResponse(
                 endpoint,
                 statusCode,
-                HttpUtils.unescape(headers.toMap()),
+                HttpUtils.unescape(headers.toLowerCaseMap()),
                 new ByteBufInputStream(retainedContent, true),
                 size);
         } else {
@@ -230,7 +230,7 @@ public StoreResponse unwrapToStoreResponse(
         return new StoreResponse(
             endpoint,
             statusCode,
-            HttpUtils.unescape(headers.toMap()),
+            HttpUtils.unescape(headers.toLowerCaseMap()),
             null,
             0);
     }
@@ -583,7 +583,7 @@ private void validateOrThrow(RxDocumentServiceRequest request,
                 String.format("%s, StatusCode: %s", cosmosError.getMessage(), statusCodeString),
                 cosmosError.getPartitionedQueryExecutionInfo());
 
-            CosmosException dce = BridgeInternal.createCosmosException(request.requestContext.resourcePhysicalAddress, statusCode, cosmosError, headers.toMap());
+            CosmosException dce = BridgeInternal.createCosmosException(request.requestContext.resourcePhysicalAddress, statusCode, cosmosError, headers.toLowerCaseMap());
             BridgeInternal.setRequestHeaders(dce, request.getHeaders());
             throw dce;
         }

sdk/cosmos/azure-cosmos/src/main/java/com/azure/cosmos/implementation/http/HttpHeaders.java

@@ -117,6 +117,19 @@ public Map<String, String> toMap() {
         return result;
     }
 
+    /**
+     * Get {@link Map} representation of the HttpHeaders collection with lower casing header name.
+     *
+     * @return the headers as map
+     */
+    public Map<String, String> toLowerCaseMap() {
+        final Map<String, String> result = new HashMap<>(headers.size());
+        for (String headerName : headers.keySet()) {
+            result.put(headerName, headers.get(headerName).value());
+        }
+        return result;
+    }
+
     @Override
     public Iterator<HttpHeader> iterator() {
         return headers.values().iterator();