source: sample/hadoop-0.17/tw/org/nchc/util/KeyValueProcess.java

Last change on this file was 20, checked in by waue, 16 years ago

將改完的 hadoop 0.17版package 放來備份
目前繼續開發 hadoop 0.16 + hbase 1.3

File size: 2.8 KB
Line 
1/*
2 * Cloud9: A MapReduce Library for Hadoop
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License"); you
5 * may not use this file except in compliance with the License. You may
6 * obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
13 * implied. See the License for the specific language governing
14 * permissions and limitations under the License.
15 */
16
17package tw.org.nchc.util;
18
19import java.util.HashMap;
20import java.util.Map;
21
22import org.apache.hadoop.io.Writable;
23import org.apache.hadoop.io.WritableComparable;
24
25/**
26 * <p>
27 * Interface that defines the callback associated with
28 * {@link SequenceFileProcessor}. For each key-value pair, the
29 * <code>SequenceFileProcessor</code> calls {@link #process}; this needs to
30 * be instantiated by the user. After all the key-value pairs are processed,
31 * <code>SequenceFileProcessor</code> calls {@link #report}; this also needs
32 * to be instantiated by the user. Results of computations are retrieved using
33 * {@link #getProperty(String)}.
34 * </p>
35 *
36 * @param <K>
37 *            type of key
38 * @param <V>
39 *            type of value
40 */
41public abstract class KeyValueProcess<K extends WritableComparable, V extends Writable> {
42  private Map<String, Object> mHash = new HashMap<String, Object>();
43
44  /**
45   * Creates a new <code>KeyValueProcess</code>
46   */
47  public KeyValueProcess() {
48  }
49
50  /**
51   * Called by {@link SequenceFileProcessor} for every key-value pair. This
52   * method needs to be defined by the user.
53   *
54   * @param key
55   *            the key
56   * @param value
57   *            the value
58   */
59  public abstract void process(K key, V value);
60
61  /**
62   * Called by {@link SequenceFileProcessor} after all key-value pairs have
63   * been processed. This methods needs to be defined by the user; typical
64   * instantiations would record results of the computation using
65   * {@link #setProperty(String, Object)}.
66   */
67  public abstract void report();
68
69  /**
70   * Sets a property. Used for recording the results of computational
71   * performed by this class.
72   *
73   * @param property
74   *            property
75   * @param value
76   *            value of the property
77   */
78  public void setProperty(String property, Object value) {
79    mHash.put(property, value);
80  }
81
82  /**
83   * Retrieves a property. Used for retrieving results of a computational
84   * performed by this class.
85   *
86   * @param property
87   *            property
88   * @return value of the property
89   */
90  public Object getProperty(String property) {
91    return mHash.get(property);
92  }
93
94}
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