| /** |
| * 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.hadoop.conf; |
| |
| import org.apache.commons.logging.*; |
| |
| import java.util.Collection; |
| |
| /** |
| * Utility base class for implementing the Reconfigurable interface. |
| * |
| * Subclasses should override reconfigurePropertyImpl to change individual |
| * properties and getReconfigurableProperties to get all properties that |
| * can be changed at run time. |
| */ |
| public abstract class ReconfigurableBase |
| extends Configured implements Reconfigurable { |
| |
| private static final Log LOG = |
| LogFactory.getLog(ReconfigurableBase.class); |
| |
| /** |
| * Construct a ReconfigurableBase. |
| */ |
| public ReconfigurableBase() { |
| super(new Configuration()); |
| } |
| |
| /** |
| * Construct a ReconfigurableBase with the {@link Configuration} |
| * conf. |
| */ |
| public ReconfigurableBase(Configuration conf) { |
| super((conf == null) ? new Configuration() : conf); |
| } |
| |
| /** |
| * {@inheritDoc} |
| * |
| * This method makes the change to this objects {@link Configuration} |
| * and calls reconfigurePropertyImpl to update internal data structures. |
| * This method cannot be overridden, subclasses should instead override |
| * reconfigureProperty. |
| */ |
| @Override |
| public final String reconfigureProperty(String property, String newVal) |
| throws ReconfigurationException { |
| if (isPropertyReconfigurable(property)) { |
| LOG.info("changing property " + property + " to " + newVal); |
| String oldVal; |
| synchronized(getConf()) { |
| oldVal = getConf().get(property); |
| reconfigurePropertyImpl(property, newVal); |
| if (newVal != null) { |
| getConf().set(property, newVal); |
| } else { |
| getConf().unset(property); |
| } |
| } |
| return oldVal; |
| } else { |
| throw new ReconfigurationException(property, newVal, |
| getConf().get(property)); |
| } |
| } |
| |
| /** |
| * {@inheritDoc} |
| * |
| * Subclasses must override this. |
| */ |
| @Override |
| public abstract Collection<String> getReconfigurableProperties(); |
| |
| |
| /** |
| * {@inheritDoc} |
| * |
| * Subclasses may wish to override this with a more efficient implementation. |
| */ |
| @Override |
| public boolean isPropertyReconfigurable(String property) { |
| return getReconfigurableProperties().contains(property); |
| } |
| |
| /** |
| * Change a configuration property. |
| * |
| * Subclasses must override this. This method applies the change to |
| * all internal data structures derived from the configuration property |
| * that is being changed. If this object owns other Reconfigurable objects |
| * reconfigureProperty should be called recursively to make sure that |
| * to make sure that the configuration of these objects is updated. |
| */ |
| protected abstract void reconfigurePropertyImpl(String property, String newVal) |
| throws ReconfigurationException; |
| |
| } |