content: /*
   * The Alluxio Open Foundation licenses this work under the Apache License, version 2.0
   * (the "License"). You may not use this work except in compliance with the License, which is
   * available at www.apache.org/licenses/LICENSE-2.0
   *
   * This software is distributed on an "AS IS" basis, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
   * either express or implied, as more fully set forth in the License.
   *
   * See the NOTICE file distributed with this work for information regarding copyright ownership.
   */
  
  package alluxio.job.plan;
  
  import alluxio.exception.ExceptionMessage;
  import alluxio.exception.JobDoesNotExistException;
  import alluxio.job.JobConfig;
  
  import com.google.common.base.Throwables;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import java.io.Serializable;
  import java.util.HashMap;
  import java.util.Map;
  import java.util.ServiceLoader;
  import javax.annotation.concurrent.ThreadSafe;
  
  /**
   * The central registry of all the job definitions.
   */
  @ThreadSafe
  public enum PlanDefinitionRegistry {
    INSTANCE;
    private static final Logger LOG = LoggerFactory.getLogger(PlanDefinitionRegistry.class);
    private final Map<Class<?>, PlanDefinition<?, ?, ?>> mDefinitions = new HashMap<>();
  
    // all the static fields must be defined before the static initialization
    static {
      // Discover and register the available definitions
      INSTANCE.discoverJobDefinitions();
    }
  
    @SuppressWarnings("unchecked")
    private void discoverJobDefinitions() {
      @SuppressWarnings({"rawtypes"})
      ServiceLoader<PlanDefinition> discoveredDefinitions =
          ServiceLoader.load(PlanDefinition.class, PlanDefinition.class.getClassLoader());
  
      for (@SuppressWarnings("rawtypes") PlanDefinition definition : discoveredDefinitions) {
        add(definition.getJobConfigClass(), definition);
        LOG.info("Loaded job definition " + definition.getClass().getSimpleName() + " for config "
            + definition.getJobConfigClass().getName());
      }
    }
  
    private PlanDefinitionRegistry() {}
  
    /*
     * Adds a mapping from the job configuration to the definition.
     */
    private <T extends JobConfig> void add(Class<T> jobConfig,
                                           PlanDefinition<T, ?, ?> definition) {
      mDefinitions.put(jobConfig, definition);
    }
  
    /**
     * Gets the job definition from the job configuration.
     *
     * @param jobConfig the job configuration
     * @param <T> the job configuration class
     * @return the job definition corresponding to the configuration
     * @throws JobDoesNotExistException when the job definition does not exist
     */
    @SuppressWarnings("unchecked")
    public synchronized <T extends JobConfig> PlanDefinition<T, Serializable, Serializable>
          getJobDefinition(T jobConfig) throws JobDoesNotExistException {
      if (!mDefinitions.containsKey(jobConfig.getClass())) {
        throw new JobDoesNotExistException(
            ExceptionMessage.JOB_DEFINITION_DOES_NOT_EXIST.getMessage(jobConfig.getName()));
      }
      try {
        return mDefinitions.get(jobConfig.getClass()).getClass().newInstance();
      } catch (InstantiationException | IllegalAccessException e) {
        throw Throwables.propagate(e);
      }
    }
  }
  