[20] | 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.tuple; |
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| 18 | |
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| 19 | import java.io.DataInput; |
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| 20 | import java.io.DataOutput; |
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| 21 | import java.io.IOException; |
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| 22 | import java.util.ArrayList; |
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| 23 | import org.apache.hadoop.io.Writable; |
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| 24 | |
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| 25 | /** |
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| 26 | * <p> |
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| 27 | * Class that represents an array list in Hadoop's data type system. It extends ArrayList class, |
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| 28 | * hence supports all services provided by ArrayList. |
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| 29 | * Elements in the list must be homogeneous and must implement Hadoop's Writable interface. |
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| 30 | * This class, combined with {@link Tuple}, allows the user to |
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| 31 | * define arbitrarily complex data structures. |
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| 32 | * </p> |
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| 33 | * |
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| 34 | * @see Tuple |
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| 35 | * @param <E> |
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| 36 | * type of list element |
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| 37 | */ |
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| 38 | |
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| 39 | public class ArrayListWritable<E extends Writable> extends ArrayList<E> implements Writable{ |
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| 40 | |
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| 41 | private static final long serialVersionUID = 1L; |
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| 42 | |
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| 43 | /** |
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| 44 | * Creates an ArrayListWritable object. |
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| 45 | */ |
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| 46 | public ArrayListWritable() { |
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| 47 | super(); |
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| 48 | } |
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| 49 | |
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| 50 | /** |
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| 51 | * Creates an ArrayListWritable object from a regular ArrayList. |
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| 52 | */ |
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| 53 | public ArrayListWritable(ArrayList<E> array) { |
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| 54 | super(array); |
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| 55 | } |
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| 56 | |
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| 57 | /** |
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| 58 | * Deserializes the array. |
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| 59 | * |
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| 60 | * @param in |
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| 61 | * source for raw byte representation |
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| 62 | */ |
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| 63 | @SuppressWarnings("unchecked") |
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| 64 | public void readFields(DataInput in) throws IOException { |
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| 65 | |
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| 66 | this.clear(); |
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| 67 | |
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| 68 | int numFields = in.readInt(); |
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| 69 | if(numFields==0) return; |
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| 70 | String className = in.readUTF(); |
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| 71 | E obj; |
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| 72 | try { |
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| 73 | Class c = Class.forName(className); |
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| 74 | for (int i = 0; i < numFields; i++) { |
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| 75 | obj = (E) c.newInstance(); |
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| 76 | obj.readFields(in); |
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| 77 | this.add(obj); |
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| 78 | } |
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| 79 | |
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| 80 | } catch (ClassNotFoundException e) { |
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| 81 | e.printStackTrace(); |
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| 82 | } catch (IllegalAccessException e) { |
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| 83 | e.printStackTrace(); |
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| 84 | } catch (InstantiationException e) { |
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| 85 | e.printStackTrace(); |
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| 86 | } |
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| 87 | } |
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| 88 | |
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| 89 | /** |
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| 90 | * Serializes this array. |
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| 91 | * |
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| 92 | * @param out |
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| 93 | * where to write the raw byte representation |
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| 94 | */ |
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| 95 | public void write(DataOutput out) throws IOException { |
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| 96 | out.writeInt(this.size()); |
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| 97 | if(size()==0) return; |
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| 98 | E obj=get(0); |
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| 99 | |
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| 100 | out.writeUTF(obj.getClass().getCanonicalName()); |
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| 101 | |
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| 102 | for (int i = 0; i < size(); i++) { |
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| 103 | obj = get(i); |
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| 104 | if (obj == null) { |
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| 105 | throw new IOException("Cannot serialize null fields!"); |
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| 106 | } |
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| 107 | obj.write(out); |
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| 108 | } |
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| 109 | } |
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| 110 | |
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| 111 | /** |
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| 112 | * Generates human-readable String representation of this ArrayList. |
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| 113 | * |
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| 114 | * @return human-readable String representation of this ArrayList |
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| 115 | */ |
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| 116 | public String toString() { |
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| 117 | StringBuffer sb = new StringBuffer(); |
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| 118 | sb.append("["); |
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| 119 | for (int i = 0; i < this.size(); i++) { |
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| 120 | if (i != 0) |
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| 121 | sb.append(", "); |
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| 122 | sb.append(this.get(i)); |
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| 123 | } |
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| 124 | sb.append("]"); |
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| 125 | |
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| 126 | return sb.toString(); |
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| 127 | } |
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| 128 | |
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| 129 | } |
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