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WordCount 实例

發布時間：2024/4/17 编程问答 49 豆豆

生活随笔收集整理的這篇文章主要介紹了 WordCount 实例小編覺得挺不錯的,現在分享給大家,幫大家做個參考.

?http://www.iteye.com/topic/606962

http://www.iteye.com/topic/1117343

看了到Hadoop的代碼，還是不知道他的執行流程，怎么辦呢。我想到了日志，在hadoop的目錄下，有log4j,那就用戶Log4j來記錄Hadoop的執行過程吧.
Java代碼 ?

import?java.io.IOException; ??

import?java.util.StringTokenizer; ??

import?org.apache.hadoop.conf.Configuration; ??

import?org.apache.hadoop.fs.Path; ??

import?org.apache.hadoop.io.IntWritable; ??

import?org.apache.hadoop.io.Text; ??

import?org.apache.hadoop.mapreduce.Job; ??

import?org.apache.hadoop.mapreduce.Mapper; ??

import?org.apache.hadoop.mapreduce.Reducer; ??

import?org.apache.hadoop.mapreduce.lib.input.FileInputFormat; ??

import?org.apache.hadoop.mapreduce.lib.output.FileOutputFormat; ??

import?org.apache.hadoop.util.GenericOptionsParser; ??

import?org.apache.log4j.Logger; ??

public?class?WordCount?{ ??

??public?static?Logger?loger?=?Wloger.loger; ??

??/** ?

???*?TokenizerMapper?繼續自?Mapper<Object,?Text,?Text,?IntWritable> ?

???* ?

???*?[一個文件就一個map,兩個文件就會有兩個map] ?

???*?map[這里讀入輸入文件內容?以"?\t\n\r\f"?進行分割，然后設置?word?==>?one?的key/value對] ?

???* ?

???*?@param?Object??Input?key?Type: ?

???*?@param?Text????Input?value?Type: ?

???*?@param?Text????Output?key?Type: ?

???*?@param?IntWritable?Output?value?Type: ?

???* ?

???*?Writable的主要特點是它使得Hadoop框架知道對一個Writable類型的對象怎樣進行serialize以及deserialize. ?

???*?WritableComparable在Writable的基礎上增加了compareT接口，使得Hadoop框架知道怎樣對WritableComparable類型的對象進行排序。 ?

???* ?

???*?@author?yangchunlong.tw ?

???* ?

???*/??

??public?static?class?TokenizerMapper ??

???????extends?Mapper<Object,?Text,?Text,?IntWritable>{ ??

????private?final?static?IntWritable?one?=?new?IntWritable(1); ??

????private?Text?word?=?new?Text(); ??

????public?void?map(Object?key,?Text?value,?Context?context ??

????????????????????)?throws?IOException,?InterruptedException?{ ??

??????loger.info("Map?<key>"+key+"</key>"); ??

??????loger.info("Map?<value>"+value+"</key>"); ??

??????StringTokenizer?itr?=?new?StringTokenizer(value.toString()); ??

??????while?(itr.hasMoreTokens())?{ ??

????????String?wordstr?=?itr.nextToken(); ??

????????word.set(wordstr); ??

????????loger.info("Map?<word>"+wordstr+"</word>"); ??

????????context.write(word,?one); ??

??????} ??

????} ??

??} ??

??/** ?

???*?IntSumReducer?繼承自?Reducer<Text,IntWritable,Text,IntWritable> ?

???* ?

???*?[不管幾個Map,都只有一個Reduce,這是一個匯總] ?

???*?reduce[循環所有的map值,把word?==>?one?的key/value對進行匯總] ?

???* ?

???*?這里的key為Mapper設置的word[每一個key/value都會有一次reduce] ?

???* ?

???*?當循環結束后，最后的確context就是最后的結果. ?

???* ?

???*?@author?yangchunlong.tw ?

???* ?

???*/??

??public?static?class?IntSumReducer ??

???????extends?Reducer<Text,IntWritable,Text,IntWritable>?{ ??

????private?IntWritable?result?=?new?IntWritable(); ??

????public?void?reduce(Text?key,?Iterable<IntWritable>?values, ??

???????????????????????Context?context ??

???????????????????????)?throws?IOException,?InterruptedException?{ ??

??????loger.info("Reduce?<key>"+key+"</key>"); ??

??????loger.info("Reduce?<value>"+values+"</key>"); ??

??????int?sum?=?0; ??

??????for?(IntWritable?val?:?values)?{ ??

????????sum?+=?val.get(); ??

??????} ??

??????result.set(sum); ??

??????loger.info("Reduce?<sum>"+sum+"</sum>"); ??

??????context.write(key,?result); ??

????} ??

??} ??

??public?static?void?main(String[]?args)?throws?Exception?{ ??

????Configuration?conf?=?new?Configuration(); ??

????String[]?otherArgs?=?new?GenericOptionsParser(conf,?args).getRemainingArgs(); ??

????/** ?

?????*?這里必須有輸入/輸出 ?

?????*/??

????if?(otherArgs.length?!=?2)?{ ??

??????System.err.println("Usage:?wordcount?<in>?<out>"); ??

??????System.exit(2); ??

????} ??

????Job?job?=?new?Job(conf,?"word?count"); ??

????job.setJarByClass(WordCount.class);//主類 ??

????job.setMapperClass(TokenizerMapper.class);//mapper ??

????job.setCombinerClass(IntSumReducer.class);//作業合成類 ??

????job.setReducerClass(IntSumReducer.class);//reducer ??

????job.setOutputKeyClass(Text.class);//設置作業輸出數據的關鍵類 ??

????job.setOutputValueClass(IntWritable.class);//設置作業輸出值類 ??

????FileInputFormat.addInputPath(job,?new?Path(otherArgs[0]));//文件輸入 ??

????FileOutputFormat.setOutputPath(job,?new?Path(otherArgs[1]));//文件輸出 ??

????System.exit(job.waitForCompletion(true)???0?:?1);//等待完成退出. ??

??} ??

}??

import java.io.IOException; import java.util.StringTokenizer;import org.apache.hadoop.conf.Configuration; import org.apache.hadoop.fs.Path; import org.apache.hadoop.io.IntWritable; import org.apache.hadoop.io.Text; import org.apache.hadoop.mapreduce.Job; import org.apache.hadoop.mapreduce.Mapper; import org.apache.hadoop.mapreduce.Reducer; import org.apache.hadoop.mapreduce.lib.input.FileInputFormat; import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat; import org.apache.hadoop.util.GenericOptionsParser; import org.apache.log4j.Logger;public class WordCount {public static Logger loger = Wloger.loger;/*** TokenizerMapper 繼續自 Mapper<Object, Text, Text, IntWritable>** [一個文件就一個map,兩個文件就會有兩個map]* map[這里讀入輸入文件內容以" \t\n\r\f" 進行分割，然后設置 word ==> one 的key/value對]** @param Object Input key Type:* @param Text Input value Type:* @param Text Output key Type:* @param IntWritable Output value Type:** Writable的主要特點是它使得Hadoop框架知道對一個Writable類型的對象怎樣進行serialize以及deserialize.* WritableComparable在Writable的基礎上增加了compareT接口，使得Hadoop框架知道怎樣對WritableComparable類型的對象進行排序。** @author yangchunlong.tw**/public static class TokenizerMapperextends Mapper<Object, Text, Text, IntWritable>{private final static IntWritable one = new IntWritable(1);private Text word = new Text();public void map(Object key, Text value, Context context) throws IOException, InterruptedException {loger.info("Map <key>"+key+"</key>");loger.info("Map <value>"+value+"</key>");StringTokenizer itr = new StringTokenizer(value.toString());while (itr.hasMoreTokens()) {String wordstr = itr.nextToken();word.set(wordstr);loger.info("Map <word>"+wordstr+"</word>");context.write(word, one);}}}/*** IntSumReducer 繼承自 Reducer<Text,IntWritable,Text,IntWritable>** [不管幾個Map,都只有一個Reduce,這是一個匯總]* reduce[循環所有的map值,把word ==> one 的key/value對進行匯總]** 這里的key為Mapper設置的word[每一個key/value都會有一次reduce]** 當循環結束后，最后的確context就是最后的結果.** @author yangchunlong.tw**/public static class IntSumReducerextends Reducer<Text,IntWritable,Text,IntWritable> {private IntWritable result = new IntWritable();public void reduce(Text key, Iterable<IntWritable> values,Context context) throws IOException, InterruptedException {loger.info("Reduce <key>"+key+"</key>");loger.info("Reduce <value>"+values+"</key>");int sum = 0;for (IntWritable val : values) {sum += val.get();}result.set(sum);loger.info("Reduce <sum>"+sum+"</sum>");context.write(key, result);}}public static void main(String[] args) throws Exception {Configuration conf = new Configuration();String[] otherArgs = new GenericOptionsParser(conf, args).getRemainingArgs();/*** 這里必須有輸入/輸出*/if (otherArgs.length != 2) {System.err.println("Usage: wordcount <in> <out>");System.exit(2);}Job job = new Job(conf, "word count");job.setJarByClass(WordCount.class);//主類job.setMapperClass(TokenizerMapper.class);//mapperjob.setCombinerClass(IntSumReducer.class);//作業合成類job.setReducerClass(IntSumReducer.class);//reducerjob.setOutputKeyClass(Text.class);//設置作業輸出數據的關鍵類job.setOutputValueClass(IntWritable.class);//設置作業輸出值類FileInputFormat.addInputPath(job, new Path(otherArgs[0]));//文件輸入FileOutputFormat.setOutputPath(job, new Path(otherArgs[1]));//文件輸出System.exit(job.waitForCompletion(true) ? 0 : 1);//等待完成退出.} }

這里輸出了每一次Map，每一次Reduce.結果如下:
Java代碼 ?

f1?==>Map?Result ??

Map?<key>0</key> ??

Map?<value>ycl?ycl?is?ycl?good</key> ??

Map?<word>ycl</word> ??

Map?<word>is</word> ??

Map?<word>ycl</word> ??

Map?<word>good</word> ??

f1?==>Reduce?Result ??

Reduce?<key>good</key> ??

Reduce?<value>org.apache.hadoop.mapreduce.ReduceContext$ValueIterable@1dfc547</key> ??

Reduce?<sum>1</sum> ??

Reduce?<key>is</key> ??

Reduce?<value>org.apache.hadoop.mapreduce.ReduceContext$ValueIterable@1dfc547</key> ??

Reduce?<sum>1</sum> ??

Reduce?<key>ycl</key> ??

Reduce?<value>org.apache.hadoop.mapreduce.ReduceContext$ValueIterable@1dfc547</key> ??

Reduce?<sum>3</sum> ??

f2?==>Map?Result ??

Map?<key>0</key> ??

Map?<value>hello?ycl?hello?lg</key> ??

Map?<word>hello</word> ??

Map?<word>ycl</word> ??

Map?<word>hello</word> ??

Map?<word>lg</word> ??

f2?==>Reduce?Result ??

Reduce?<key>hello</key> ??

Reduce?<value>org.apache.hadoop.mapreduce.ReduceContext$ValueIterable@10f6d3</key> ??

Reduce?<sum>2</sum> ??

Reduce?<key>lg</key> ??

Reduce?<value>org.apache.hadoop.mapreduce.ReduceContext$ValueIterable@10f6d3</key> ??

Reduce?<sum>1</sum> ??

Reduce?<key>ycl</key> ??

Reduce?<value>org.apache.hadoop.mapreduce.ReduceContext$ValueIterable@10f6d3</key> ??

Reduce?<sum>1</sum> ??

f1,f2?==>?Reduce?Result ??

Reduce?<key>good</key> ??