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.beam.sdk.schemas.io;
  
  import static org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.base.Preconditions.checkState;
  
  import java.util.HashMap;
  import java.util.Map;
  import java.util.ServiceLoader;
  import org.apache.beam.sdk.annotations.Internal;
  
  /** Helpers for implementing the "Provider" pattern. */
  @Internal
  public final class Providers {
  
    public interface Identifyable {
      /**
       * Returns an id that uniquely represents this among others implementing its derived interface.
       */
      String identifier();
    }
  
    private Providers() {}
  
    public static <T extends Identifyable> Map<String, T> loadProviders(Class<T> klass) {
      Map<String, T> providers = new HashMap<>();
      for (T provider : ServiceLoader.load(klass)) {
        checkState(
            !providers.containsKey(provider.identifier()),
            "Duplicate providers exist with identifier `%s` for class %s.",
            provider.identifier(),
            klass);
        providers.put(provider.identifier(), provider);
      }
      return providers;
    }
  }
  