001 /**
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements. See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership. The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License. You may obtain a copy of the License at
009 *
010 * http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing, software
013 * distributed under the License is distributed on an "AS IS" BASIS,
014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015 * See the License for the specific language governing permissions and
016 * limitations under the License.
017 */
018
019 package org.apache.hadoop.io;
020
021 import org.apache.hadoop.classification.InterfaceAudience;
022 import org.apache.hadoop.classification.InterfaceStability;
023 import org.apache.hadoop.conf.*;
024 import org.apache.hadoop.util.ReflectionUtils;
025 import java.util.HashMap;
026
027 /** Factories for non-public writables. Defining a factory permits {@link
028 * ObjectWritable} to be able to construct instances of non-public classes. */
029 @InterfaceAudience.Public
030 @InterfaceStability.Stable
031 public class WritableFactories {
032 private static final HashMap<Class, WritableFactory> CLASS_TO_FACTORY =
033 new HashMap<Class, WritableFactory>();
034
035 private WritableFactories() {} // singleton
036
037 /** Define a factory for a class. */
038 public static synchronized void setFactory(Class c, WritableFactory factory) {
039 CLASS_TO_FACTORY.put(c, factory);
040 }
041
042 /** Define a factory for a class. */
043 public static synchronized WritableFactory getFactory(Class c) {
044 return CLASS_TO_FACTORY.get(c);
045 }
046
047 /** Create a new instance of a class with a defined factory. */
048 public static Writable newInstance(Class<? extends Writable> c, Configuration conf) {
049 WritableFactory factory = WritableFactories.getFactory(c);
050 if (factory != null) {
051 Writable result = factory.newInstance();
052 if (result instanceof Configurable) {
053 ((Configurable) result).setConf(conf);
054 }
055 return result;
056 } else {
057 return ReflectionUtils.newInstance(c, conf);
058 }
059 }
060
061 /** Create a new instance of a class with a defined factory. */
062 public static Writable newInstance(Class<? extends Writable> c) {
063 return newInstance(c, null);
064 }
065
066 }
067