diff --git a/xds/src/main/java/io/grpc/xds/StructOrError.java b/xds/src/main/java/io/grpc/xds/StructOrError.java
new file mode 100644
index 0000000000..14f008d191
--- /dev/null
+++ b/xds/src/main/java/io/grpc/xds/StructOrError.java
@@ -0,0 +1,72 @@
+/*
+ * Copyright 2024 The gRPC Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.grpc.xds;
+
+import static com.google.common.base.Preconditions.checkNotNull;
+
+import com.google.common.annotations.VisibleForTesting;
+import javax.annotation.Nullable;
+
+/** An object or a String error. */
+final class StructOrError<T> {
+
+  /**
+  * Returns a {@link StructOrError} for the successfully converted data object.
+  */
+  public static <T> StructOrError<T> fromStruct(T struct) {
+    return new StructOrError<>(struct);
+  }
+
+  /**
+   * Returns a {@link StructOrError} for the failure to convert the data object.
+   */
+  public static <T> StructOrError<T> fromError(String errorDetail) {
+    return new StructOrError<>(errorDetail);
+  }
+
+  private final String errorDetail;
+  private final T struct;
+
+  private StructOrError(T struct) {
+    this.struct = checkNotNull(struct, "struct");
+    this.errorDetail = null;
+  }
+
+  private StructOrError(String errorDetail) {
+    this.struct = null;
+    this.errorDetail = checkNotNull(errorDetail, "errorDetail");
+  }
+
+  /**
+   * Returns struct if exists, otherwise null.
+   */
+  @VisibleForTesting
+  @Nullable
+  public T getStruct() {
+    return struct;
+  }
+
+  /**
+   * Returns error detail if exists, otherwise null.
+   */
+  @VisibleForTesting
+  @Nullable
+  public String getErrorDetail() {
+    return errorDetail;
+  }
+}
+
diff --git a/xds/src/main/java/io/grpc/xds/XdsClusterResource.java b/xds/src/main/java/io/grpc/xds/XdsClusterResource.java
index c7789f3d7d..e1645063c4 100644
--- a/xds/src/main/java/io/grpc/xds/XdsClusterResource.java
+++ b/xds/src/main/java/io/grpc/xds/XdsClusterResource.java
@@ -67,6 +67,8 @@ class XdsClusterResource extends XdsResourceType<CdsUpdate> {
   static final String AGGREGATE_CLUSTER_TYPE_NAME = "envoy.clusters.aggregate";
   static final String ADS_TYPE_URL_CDS =
       "type.googleapis.com/envoy.config.cluster.v3.Cluster";
+  private static final String TYPE_URL_CLUSTER_CONFIG =
+      "type.googleapis.com/envoy.extensions.clusters.aggregate.v3.ClusterConfig";
   private static final String TYPE_URL_UPSTREAM_TLS_CONTEXT =
       "type.googleapis.com/envoy.extensions.transport_sockets.tls.v3.UpstreamTlsContext";
   private static final String TYPE_URL_UPSTREAM_TLS_CONTEXT_V2 =
diff --git a/xds/src/main/java/io/grpc/xds/XdsRouteConfigureResource.java b/xds/src/main/java/io/grpc/xds/XdsRouteConfigureResource.java
index 0e065c6ba9..587c7a437a 100644
--- a/xds/src/main/java/io/grpc/xds/XdsRouteConfigureResource.java
+++ b/xds/src/main/java/io/grpc/xds/XdsRouteConfigureResource.java
@@ -78,6 +78,8 @@ class XdsRouteConfigureResource extends XdsResourceType<RdsUpdate> {
       "type.googleapis.com/envoy.config.route.v3.RouteConfiguration";
   private static final String TYPE_URL_FILTER_CONFIG =
       "type.googleapis.com/envoy.config.route.v3.FilterConfig";
+  @VisibleForTesting
+  static final String HASH_POLICY_FILTER_STATE_KEY = "io.grpc.channel_id";
   // TODO(zdapeng): need to discuss how to handle unsupported values.
   private static final Set<Status.Code> SUPPORTED_RETRYABLE_CODES =
       Collections.unmodifiableSet(EnumSet.of(
diff --git a/xds/src/main/java/io/grpc/xds/client/XdsResourceType.java b/xds/src/main/java/io/grpc/xds/client/XdsResourceType.java
index 8c3d31604e..ccb622ff16 100644
--- a/xds/src/main/java/io/grpc/xds/client/XdsResourceType.java
+++ b/xds/src/main/java/io/grpc/xds/client/XdsResourceType.java
@@ -20,7 +20,6 @@ import static com.google.common.base.Preconditions.checkNotNull;
 import static io.grpc.xds.client.XdsClient.canonifyResourceName;
 import static io.grpc.xds.client.XdsClient.isResourceNameValid;
 
-import com.google.common.annotations.VisibleForTesting;
 import com.google.protobuf.Any;
 import com.google.protobuf.InvalidProtocolBufferException;
 import com.google.protobuf.Message;
@@ -41,11 +40,7 @@ public abstract class XdsResourceType<T extends ResourceUpdate> {
   static final String TYPE_URL_RESOURCE =
       "type.googleapis.com/envoy.service.discovery.v3.Resource";
   protected static final String TRANSPORT_SOCKET_NAME_TLS = "envoy.transport_sockets.tls";
-  @VisibleForTesting
-  public static final String HASH_POLICY_FILTER_STATE_KEY = "io.grpc.channel_id";
 
-  protected static final String TYPE_URL_CLUSTER_CONFIG =
-      "type.googleapis.com/envoy.extensions.clusters.aggregate.v3.ClusterConfig";
   protected static final String TYPE_URL_TYPED_STRUCT_UDPA =
       "type.googleapis.com/udpa.type.v1.TypedStruct";
   protected static final String TYPE_URL_TYPED_STRUCT =
@@ -249,53 +244,4 @@ public abstract class XdsResourceType<T extends ResourceUpdate> {
       this.errors = errors;
     }
   }
-
-  @VisibleForTesting
-  public static final class StructOrError<T> {
-
-    /**
-    * Returns a {@link StructOrError} for the successfully converted data object.
-    */
-    public static <T> StructOrError<T> fromStruct(T struct) {
-      return new StructOrError<>(struct);
-    }
-
-    /**
-     * Returns a {@link StructOrError} for the failure to convert the data object.
-     */
-    public static <T> StructOrError<T> fromError(String errorDetail) {
-      return new StructOrError<>(errorDetail);
-    }
-
-    private final String errorDetail;
-    private final T struct;
-
-    private StructOrError(T struct) {
-      this.struct = checkNotNull(struct, "struct");
-      this.errorDetail = null;
-    }
-
-    private StructOrError(String errorDetail) {
-      this.struct = null;
-      this.errorDetail = checkNotNull(errorDetail, "errorDetail");
-    }
-
-    /**
-     * Returns struct if exists, otherwise null.
-     */
-    @VisibleForTesting
-    @Nullable
-    public T getStruct() {
-      return struct;
-    }
-
-    /**
-     * Returns error detail if exists, otherwise null.
-     */
-    @VisibleForTesting
-    @Nullable
-    public String getErrorDetail() {
-      return errorDetail;
-    }
-  }
 }
diff --git a/xds/src/test/java/io/grpc/xds/GrpcXdsClientImplDataTest.java b/xds/src/test/java/io/grpc/xds/GrpcXdsClientImplDataTest.java
index b0ef0131a6..6b905c4e2b 100644
--- a/xds/src/test/java/io/grpc/xds/GrpcXdsClientImplDataTest.java
+++ b/xds/src/test/java/io/grpc/xds/GrpcXdsClientImplDataTest.java
@@ -140,7 +140,6 @@ import io.grpc.xds.client.Bootstrapper.ServerInfo;
 import io.grpc.xds.client.XdsClient;
 import io.grpc.xds.client.XdsResourceType;
 import io.grpc.xds.client.XdsResourceType.ResourceInvalidException;
-import io.grpc.xds.client.XdsResourceType.StructOrError;
 import io.grpc.xds.internal.Matchers;
 import io.grpc.xds.internal.Matchers.FractionMatcher;
 import io.grpc.xds.internal.Matchers.HeaderMatcher;
@@ -939,7 +938,7 @@ public class GrpcXdsClientImplDataTest {
                 io.envoyproxy.envoy.config.route.v3.RouteAction.HashPolicy.newBuilder()
                     .setFilterState(
                         FilterState.newBuilder()
-                            .setKey(XdsResourceType.HASH_POLICY_FILTER_STATE_KEY)))
+                            .setKey(XdsRouteConfigureResource.HASH_POLICY_FILTER_STATE_KEY)))
             .addHashPolicy(
                 io.envoyproxy.envoy.config.route.v3.RouteAction.HashPolicy.newBuilder()
                     .setQueryParameter(