WritableFactories.java
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上传日期:2018-01-08
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- /**
- * 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.io;
- import org.apache.hadoop.conf.*;
- import org.apache.hadoop.util.ReflectionUtils;
- import java.util.HashMap;
- /** Factories for non-public writables. Defining a factory permits {@link
- * ObjectWritable} to be able to construct instances of non-public classes. */
- public class WritableFactories {
- private static final HashMap<Class, WritableFactory> CLASS_TO_FACTORY =
- new HashMap<Class, WritableFactory>();
- private WritableFactories() {} // singleton
- /** Define a factory for a class. */
- public static synchronized void setFactory(Class c, WritableFactory factory) {
- CLASS_TO_FACTORY.put(c, factory);
- }
- /** Define a factory for a class. */
- public static synchronized WritableFactory getFactory(Class c) {
- return CLASS_TO_FACTORY.get(c);
- }
- /** Create a new instance of a class with a defined factory. */
- public static Writable newInstance(Class<? extends Writable> c, Configuration conf) {
- WritableFactory factory = WritableFactories.getFactory(c);
- if (factory != null) {
- Writable result = factory.newInstance();
- if (result instanceof Configurable) {
- ((Configurable) result).setConf(conf);
- }
- return result;
- } else {
- return ReflectionUtils.newInstance(c, conf);
- }
- }
-
- /** Create a new instance of a class with a defined factory. */
- public static Writable newInstance(Class<? extends Writable> c) {
- return newInstance(c, null);
- }
- }