1 | /* |
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2 | * Cloud9: A MapReduce Library for Hadoop |
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3 | * |
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4 | * Licensed under the Apache License, Version 2.0 (the "License"); you |
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5 | * may not use this file except in compliance with the License. You may |
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6 | * obtain a copy of the License at |
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7 | * |
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8 | * http://www.apache.org/licenses/LICENSE-2.0 |
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9 | * |
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10 | * Unless required by applicable law or agreed to in writing, software |
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11 | * distributed under the License is distributed on an "AS IS" BASIS, |
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12 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or |
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13 | * implied. See the License for the specific language governing |
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14 | * permissions and limitations under the License. |
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15 | */ |
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16 | |
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17 | package tw.org.nchc.util; |
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18 | |
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19 | import java.util.HashMap; |
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20 | import java.util.Map; |
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21 | |
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22 | import org.apache.hadoop.io.Writable; |
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23 | import org.apache.hadoop.io.WritableComparable; |
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24 | |
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25 | /** |
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26 | * <p> |
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27 | * Interface that defines the callback associated with |
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28 | * {@link SequenceFileProcessor}. For each key-value pair, the |
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29 | * <code>SequenceFileProcessor</code> calls {@link #process}; this needs to |
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30 | * be instantiated by the user. After all the key-value pairs are processed, |
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31 | * <code>SequenceFileProcessor</code> calls {@link #report}; this also needs |
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32 | * to be instantiated by the user. Results of computations are retrieved using |
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33 | * {@link #getProperty(String)}. |
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34 | * </p> |
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35 | * |
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36 | * @param <K> |
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37 | * type of key |
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38 | * @param <V> |
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39 | * type of value |
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40 | */ |
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41 | public abstract class KeyValueProcess<K extends WritableComparable, V extends Writable> { |
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42 | private Map<String, Object> mHash = new HashMap<String, Object>(); |
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43 | |
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44 | /** |
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45 | * Creates a new <code>KeyValueProcess</code> |
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46 | */ |
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47 | public KeyValueProcess() { |
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48 | } |
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49 | |
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50 | /** |
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51 | * Called by {@link SequenceFileProcessor} for every key-value pair. This |
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52 | * method needs to be defined by the user. |
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53 | * |
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54 | * @param key |
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55 | * the key |
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56 | * @param value |
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57 | * the value |
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58 | */ |
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59 | public abstract void process(K key, V value); |
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60 | |
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61 | /** |
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62 | * Called by {@link SequenceFileProcessor} after all key-value pairs have |
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63 | * been processed. This methods needs to be defined by the user; typical |
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64 | * instantiations would record results of the computation using |
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65 | * {@link #setProperty(String, Object)}. |
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66 | */ |
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67 | public abstract void report(); |
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68 | |
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69 | /** |
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70 | * Sets a property. Used for recording the results of computational |
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71 | * performed by this class. |
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72 | * |
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73 | * @param property |
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74 | * property |
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75 | * @param value |
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76 | * value of the property |
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77 | */ |
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78 | public void setProperty(String property, Object value) { |
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79 | mHash.put(property, value); |
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80 | } |
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81 | |
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82 | /** |
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83 | * Retrieves a property. Used for retrieving results of a computational |
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84 | * performed by this class. |
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85 | * |
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86 | * @param property |
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87 | * property |
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88 | * @return value of the property |
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89 | */ |
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90 | public Object getProperty(String property) { |
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91 | return mHash.get(property); |
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92 | } |
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93 | |
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94 | } |
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