content: /*
   * 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.bookkeeper.common.resolver;
  
  import static com.google.common.base.Preconditions.checkState;
  
  import io.grpc.NameResolver;
  import io.grpc.NameResolverProvider;
  import java.net.URI;
  import java.util.List;
  
  /**
   * A {@link io.grpc.NameResolverProvider} based {@link NameResolver.Factory}.
   */
  public class NameResolverProviderFactory extends NameResolver.Factory {
  
      private final List<NameResolverProvider> providers;
  
      public NameResolverProviderFactory(List<NameResolverProvider> providers) {
          this.providers = providers;
      }
  
      @Override
      public NameResolver newNameResolver(URI targetUri, NameResolver.Args params) {
          checkForProviders();
          for (NameResolverProvider provider : providers) {
              NameResolver resolver = provider.newNameResolver(targetUri, params);
              if (resolver != null) {
                  return resolver;
              }
          }
          return null;
      }
  
      @Override
      public String getDefaultScheme() {
          checkForProviders();
          return providers.get(0).getDefaultScheme();
      }
  
      private void checkForProviders() {
          checkState(!providers.isEmpty(),
              "No NameResolverProviders found. Please check your configuration");
      }
  
  }
  