mapreduce代码备忘

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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;public class WordCount{        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{                        StringTokenizer itr = new StringTokenizer(value.toString());                        while (itr.hasMoreTokens()){                                word.set(itr.nextToken());                                context.write(word,one);                        }                }        }        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{                        int sum = 0;                        for (IntWritable val : values)                        {                                sum += val.get();                        }                        result.set(sum);                        context.write(key,result);                }        }        public static void main(String[] args) throws Exception{                Configuration conf = new Configuration();                String[] otherArgs = new GenericOptionsParser(conf,args).getRemainingArgs();                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);                job.setMapperClass(TokenizerMapper.class);                job.setCombinerClass(IntSumReducer.class);                job.setReducerClass(IntSumReducer.class);                job.setOutputKeyClass(Text.class);                job.setOutputValueClass(IntWritable.class);                FileInputFormat.addInputPath(job,new Path(otherArgs[0]));                FileOutputFormat.setOutputPath(job,new Path(otherArgs[1]));                System.exit(job.waitForCompletion(true)?0:1);        }}

编译java源代码

[hadoop@localhost code]$ javac -classpath /usr/local/hadoop/hadoop-core-1.2.1.jar:/usr/local/hadoop/lib/commons-cli-1.2.jar WordCount.java

打包

[hadoop@localhost code]$ jar -cvf wordcount.jar *.class

执行程序

[hadoop@localhost code]$ ./bin/hadoop jar ./code/wordcount.jar WordCount input/ output/

查看结果

[hadoop@localhost code]$ ./bin/hadoop fs -cat output/*

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