org.apache.hadoop.io.WritableFactories.java Source code

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Here is the source code for org.apache.hadoop.io.WritableFactories.java

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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.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
import org.apache.hadoop.conf.*;
import org.apache.hadoop.util.ReflectionUtils;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;

/** Factories for non-public writables.  Defining a factory permits {@link
 * ObjectWritable} to be able to construct instances of non-public classes. */
@InterfaceAudience.Public
@InterfaceStability.Stable
public class WritableFactories {
    private static final Map<Class, WritableFactory> CLASS_TO_FACTORY = new ConcurrentHashMap<Class, WritableFactory>();

    private WritableFactories() {
    } // singleton

    /** Define a factory for a class. */
    public static void setFactory(Class c, WritableFactory factory) {
        CLASS_TO_FACTORY.put(c, factory);
    }

    /** Define a factory for a class. */
    public static 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);
    }

}