1 | /** |
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2 | * Licensed to the Apache Software Foundation (ASF) under one |
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3 | * or more contributor license agreements. See the NOTICE file |
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4 | * distributed with this work for additional information |
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5 | * regarding copyright ownership. The ASF licenses this file |
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6 | * to you under the Apache License, Version 2.0 (the |
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7 | * "License"); you may not use this file except in compliance |
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8 | * with the License. You may obtain a copy of the License at |
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9 | * |
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10 | * http://www.apache.org/licenses/LICENSE-2.0 |
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11 | * |
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12 | * Unless required by applicable law or agreed to in writing, software |
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13 | * distributed under the License is distributed on an "AS IS" BASIS, |
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14 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
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15 | * See the License for the specific language governing permissions and |
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16 | * limitations under the License. |
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17 | */ |
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18 | |
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19 | package org.apache.hadoop.io; |
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20 | |
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21 | import org.apache.hadoop.conf.*; |
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22 | import org.apache.hadoop.util.ReflectionUtils; |
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23 | import java.util.HashMap; |
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24 | |
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25 | /** Factories for non-public writables. Defining a factory permits {@link |
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26 | * ObjectWritable} to be able to construct instances of non-public classes. */ |
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27 | public class WritableFactories { |
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28 | private static final HashMap<Class, WritableFactory> CLASS_TO_FACTORY = |
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29 | new HashMap<Class, WritableFactory>(); |
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30 | |
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31 | private WritableFactories() {} // singleton |
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32 | |
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33 | /** Define a factory for a class. */ |
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34 | public static synchronized void setFactory(Class c, WritableFactory factory) { |
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35 | CLASS_TO_FACTORY.put(c, factory); |
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36 | } |
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37 | |
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38 | /** Define a factory for a class. */ |
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39 | public static synchronized WritableFactory getFactory(Class c) { |
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40 | return CLASS_TO_FACTORY.get(c); |
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41 | } |
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42 | |
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43 | /** Create a new instance of a class with a defined factory. */ |
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44 | public static Writable newInstance(Class<? extends Writable> c, Configuration conf) { |
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45 | WritableFactory factory = WritableFactories.getFactory(c); |
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46 | if (factory != null) { |
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47 | Writable result = factory.newInstance(); |
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48 | if (result instanceof Configurable) { |
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49 | ((Configurable) result).setConf(conf); |
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50 | } |
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51 | return result; |
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52 | } else { |
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53 | return ReflectionUtils.newInstance(c, conf); |
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54 | } |
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55 | } |
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56 | |
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57 | /** Create a new instance of a class with a defined factory. */ |
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58 | public static Writable newInstance(Class<? extends Writable> c) { |
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59 | return newInstance(c, null); |
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60 | } |
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61 | |
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62 | } |
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63 | |
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