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.expansion;
  
  import java.lang.reflect.Constructor;
  import java.util.Map;
  import java.util.Map.Entry;
  import org.apache.beam.sdk.transforms.ExternalTransformBuilder;
  import org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.base.Preconditions;
  import org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.collect.ImmutableMap;
  
  /**
   * A registrar which contains a mapping from URNs to available {@link ExternalTransformBuilder}s.
   * Should be used with {@link com.google.auto.service.AutoService}.
   */
  @SuppressWarnings({
    "rawtypes" // TODO(https://github.com/apache/beam/issues/20447)
  })
  public interface ExternalTransformRegistrar {
  
    /**
     * A mapping from URN to an {@link ExternalTransformBuilder} class.
     *
     * @deprecated Prefer implementing 'knownBuilderInstances'. This method will be removed in a
     *     future version of Beam.
     */
    @Deprecated
    default Map<String, Class<? extends ExternalTransformBuilder<?, ?, ?>>> knownBuilders() {
      return ImmutableMap.<String, Class<? extends ExternalTransformBuilder<?, ?, ?>>>builder()
          .build();
    }
  
    /** A mapping from URN to an {@link ExternalTransformBuilder} instance. */
    default Map<String, ExternalTransformBuilder<?, ?, ?>> knownBuilderInstances() {
      ImmutableMap.Builder builder = ImmutableMap.<String, ExternalTransformBuilder>builder();
      Map<String, Class<? extends ExternalTransformBuilder<?, ?, ?>>> knownBuilders = knownBuilders();
      for (Entry<String, Class<? extends ExternalTransformBuilder<?, ?, ?>>> knownBuilder :
          knownBuilders.entrySet()) {
        Preconditions.checkState(
            ExternalTransformBuilder.class.isAssignableFrom(knownBuilder.getValue()),
            "Provided identifier %s is not an ExternalTransformBuilder.",
            knownBuilder.getValue().getName());
        try {
          Constructor<? extends ExternalTransformBuilder> constructor =
              knownBuilder.getValue().getDeclaredConstructor();
  
          constructor.setAccessible(true);
          builder.put(knownBuilder.getKey(), constructor.newInstance());
  
        } catch (RuntimeException e) {
          throw e;
        } catch (Exception e) {
          throw new RuntimeException(
              "Unable to instantiate ExternalTransformBuilder from constructor.", e);
        }
      }
      return builder.build();
    }
  }
  