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.distributedlog.feature;
  
  import java.io.IOException;
  import java.lang.reflect.Constructor;
  import java.lang.reflect.InvocationTargetException;
  import org.apache.bookkeeper.feature.CacheableFeatureProvider;
  import org.apache.bookkeeper.feature.Feature;
  import org.apache.bookkeeper.feature.FeatureProvider;
  import org.apache.bookkeeper.stats.StatsLogger;
  import org.apache.commons.configuration2.ex.ConfigurationException;
  import org.apache.distributedlog.DistributedLogConfiguration;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  
  
  /**
   * Decider based feature provider.
   */
  public abstract class AbstractFeatureProvider<T extends Feature> extends CacheableFeatureProvider<T> {
  
      private static final Logger logger = LoggerFactory.getLogger(AbstractFeatureProvider.class);
  
      public static FeatureProvider getFeatureProvider(String rootScope,
                                                       DistributedLogConfiguration conf,
                                                       StatsLogger statsLogger)
              throws IOException {
          Class<? extends FeatureProvider> featureProviderClass;
          try {
              featureProviderClass = conf.getFeatureProviderClass();
          } catch (ConfigurationException e) {
              throw new IOException("Can't initialize the feature provider : ", e);
          }
          // create feature provider
          Constructor<? extends FeatureProvider> constructor;
          try {
              constructor = featureProviderClass.getDeclaredConstructor(
                      String.class,
                      DistributedLogConfiguration.class,
                      StatsLogger.class);
          } catch (NoSuchMethodException e) {
              throw new IOException("No constructor found for feature provider class " + featureProviderClass + " : ", e);
          }
          try {
              return constructor.newInstance(rootScope, conf, statsLogger);
          } catch (InstantiationException e) {
              throw new IOException("Failed to instantiate feature provider : ", e);
          } catch (IllegalAccessException e) {
              throw new IOException("Encountered illegal access when instantiating feature provider : ", e);
          } catch (InvocationTargetException e) {
              Throwable targetException = e.getTargetException();
              if (targetException instanceof IOException) {
                  throw (IOException) targetException;
              } else {
                  throw new IOException("Encountered invocation target"
                          + " exception while instantiating feature provider : ", e);
              }
          }
      }
  
      protected final DistributedLogConfiguration conf;
      protected final StatsLogger statsLogger;
  
      protected AbstractFeatureProvider(String rootScope,
                                        DistributedLogConfiguration conf,
                                        StatsLogger statsLogger) {
          super(rootScope);
          this.conf = conf;
          this.statsLogger = statsLogger;
      }
  
      /**
       * Start the feature provider.
       *
       * @throws IOException when failed to start the feature provider.
       */
      public void start() throws IOException {
          // no-op
      }
  
      /**
       * Stop the feature provider.
       */
      public void stop() {
          // no-op
      }
  
  }
  