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.kafka.connect.runtime.isolation;
  
  import org.apache.kafka.common.config.provider.ConfigProvider;
  import org.apache.kafka.connect.connector.policy.ConnectorClientConfigOverridePolicy;
  import org.apache.kafka.connect.rest.ConnectRestExtension;
  import org.apache.kafka.connect.sink.SinkConnector;
  import org.apache.kafka.connect.source.SourceConnector;
  import org.apache.kafka.connect.storage.Converter;
  import org.apache.kafka.connect.storage.HeaderConverter;
  import org.apache.kafka.connect.transforms.Transformation;
  import org.apache.kafka.connect.transforms.predicates.Predicate;
  
  import java.util.ServiceLoader;
  import java.util.SortedSet;
  
  /**
   * A {@link PluginScanner} implementation which uses {@link ServiceLoader} to discover plugins.
   * <p>This implements the modern discovery strategy, which uses only service loading in order to discover plugins.
   * Specifically, a plugin appears in the scan result if all the following conditions are true:
   * <ul>
   *     <li>The class and direct dependencies can be loaded</li>
   *     <li>The class is concrete</li>
   *     <li>The class is public</li>
   *     <li>The class has a no-args constructor</li>
   *     <li>The no-args constructor is public</li>
   *     <li>Static initialization of the class completes without throwing an exception</li>
   *     <li>The no-args constructor completes without throwing an exception</li>
   *     <li>The class is a subclass of {@link SinkConnector}, {@link SourceConnector}, {@link Converter},
   *         {@link HeaderConverter}, {@link Transformation}, {@link Predicate}, {@link ConfigProvider},
   *         {@link ConnectRestExtension}, or {@link ConnectorClientConfigOverridePolicy}
   *     </li>
   *     <li>The class has a {@link ServiceLoader} compatible manifest file or module declaration</li>
   * </ul>
   * <p>Note: This scanner can only find plugins with corresponding {@link ServiceLoader} manifests, which are
   * not required to be packaged with plugins. This has the effect that some plugins discoverable by the
   * {@link ReflectionScanner} may not be visible with this implementation.
   */
  public class ServiceLoaderScanner extends PluginScanner {
  
      @Override
      protected PluginScanResult scanPlugins(PluginSource source) {
          return new PluginScanResult(
                  getServiceLoaderPluginDesc(PluginType.SINK, source),
                  getServiceLoaderPluginDesc(PluginType.SOURCE, source),
                  getServiceLoaderPluginDesc(PluginType.CONVERTER, source),
                  getServiceLoaderPluginDesc(PluginType.HEADER_CONVERTER, source),
                  getTransformationPluginDesc(source),
                  getPredicatePluginDesc(source),
                  getServiceLoaderPluginDesc(PluginType.CONFIGPROVIDER, source),
                  getServiceLoaderPluginDesc(PluginType.REST_EXTENSION, source),
                  getServiceLoaderPluginDesc(PluginType.CONNECTOR_CLIENT_CONFIG_OVERRIDE_POLICY, source)
          );
      }
  
      @SuppressWarnings({"unchecked"})
      private SortedSet<PluginDesc<Predicate<?>>> getPredicatePluginDesc(PluginSource source) {
          return (SortedSet<PluginDesc<Predicate<?>>>) (SortedSet<?>) getServiceLoaderPluginDesc(PluginType.PREDICATE, source);
      }
  
      @SuppressWarnings({"unchecked"})
      private SortedSet<PluginDesc<Transformation<?>>> getTransformationPluginDesc(PluginSource source) {
          return (SortedSet<PluginDesc<Transformation<?>>>) (SortedSet<?>) getServiceLoaderPluginDesc(PluginType.TRANSFORMATION, source);
      }
  }
  