HDFS-14577. RBF: FederationUtil#newInstance should allow constructor …

…without context. Contributed by CR Hota.

hadoop-hdfs-project/hadoop-hdfs-rbf/src/main/java/org/apache/hadoop/hdfs/server/federation/router/FederationUtil.java

@@ -149,9 +149,16 @@ private static <T, R> T newInstance(final Configuration conf,
       final R context, final Class<R> contextClass, final Class<T> clazz) {
     try {
       if (contextClass == null) {
-        // Default constructor if no context
-        Constructor<T> constructor = clazz.getConstructor();
-        return constructor.newInstance();
+        if (conf == null) {
+          // Default constructor if no context
+          Constructor<T> constructor = clazz.getConstructor();
+          return constructor.newInstance();
+        } else {
+          // Constructor with configuration but no context
+          Constructor<T> constructor = clazz.getConstructor(
+              Configuration.class);
+          return constructor.newInstance(conf);
+        }
       } else {
         // Constructor with context
         Constructor<T> constructor = clazz.getConstructor(

hadoop-hdfs-project/hadoop-hdfs-rbf/src/test/java/org/apache/hadoop/hdfs/server/federation/router/TestFederationUtil.java

@@ -0,0 +1,69 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you 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 org.apache.hadoop.hdfs.server.federation.router;
+
+import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.hdfs.HdfsConfiguration;
+import org.apache.hadoop.hdfs.server.federation.MockResolver;
+import org.apache.hadoop.hdfs.server.federation.resolver.ActiveNamenodeResolver;
+import org.apache.hadoop.hdfs.server.federation.resolver.FileSubclusterResolver;
+import org.apache.hadoop.hdfs.server.federation.store.StateStoreService;
+import org.junit.Test;
+
+import static org.junit.Assert.assertNotNull;
+import static org.apache.hadoop.hdfs.server.federation.router.RBFConfigKeys.FEDERATION_FILE_RESOLVER_CLIENT_CLASS;
+import static org.apache.hadoop.hdfs.server.federation.router.RBFConfigKeys.FEDERATION_NAMENODE_RESOLVER_CLIENT_CLASS;
+
+/**
+ * Tests Router federation utility methods.
+ */
+public class TestFederationUtil {
+
+  @Test
+  public void testInstanceCreation() {
+    Configuration conf = new HdfsConfiguration();
+
+    // Use mock resolver classes
+    conf.setClass(FEDERATION_NAMENODE_RESOLVER_CLIENT_CLASS,
+        MockResolver.class, ActiveNamenodeResolver.class);
+    conf.setClass(FEDERATION_FILE_RESOLVER_CLIENT_CLASS,
+        MockResolver.class, FileSubclusterResolver.class);
+
+    Router router = new Router();
+    StateStoreService stateStore = new StateStoreService();
+
+    ActiveNamenodeResolver namenodeResolverWithContext =
+        FederationUtil.newActiveNamenodeResolver(conf, stateStore);
+
+    ActiveNamenodeResolver namenodeResolverWithoutContext =
+        FederationUtil.newActiveNamenodeResolver(conf, null);
+
+    FileSubclusterResolver subclusterResolverWithContext =
+        FederationUtil.newFileSubclusterResolver(conf, router);
+
+    FileSubclusterResolver subclusterResolverWithoutContext =
+        FederationUtil.newFileSubclusterResolver(conf, null);
+
+    // Check all instances are created successfully.
+    assertNotNull(namenodeResolverWithContext);
+    assertNotNull(namenodeResolverWithoutContext);
+    assertNotNull(subclusterResolverWithContext);
+    assertNotNull(subclusterResolverWithoutContext);
+  }
+}