Hadoop--计算平均值
package com.smartmap.example; 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.DoubleWritable; import org.apache.hadoop.io.IntWritable; import org.apache.hadoop.io.LongWritable; 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.Reducer.Context; import org.apache.hadoop.mapreduce.lib.input.FileInputFormat; import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat; import org.apache.hadoop.util.GenericOptionsParser; public class AverageByAttribute { public static class MapClass extends Mapper<LongWritable, Text, Text, Text> { public void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException { String fields[] = value.toString().split(",", -20); String country = fields[4]; String numClaims = fields[8]; if (numClaims.length() > 0 && !numClaims.startsWith("\"")) { context.write(new Text(country),new Text(numClaims + ",1")); } } public static class ReducerClass extends Reducer<Text, Text, Text, DoubleWritable> { public void reduce(Text key, Iterable<Text> values, Context context) throws IOException, InterruptedException { double sum = 0; int count = 0; for(Text val : values) { String fields[] = val.toString().split(","); sum += Double.parseDouble(fields[0]); count += Integer.parseInt(fields[1]); } context.write(key, new DoubleWritable(sum/count)); } } public static class CombineClass extends Reducer<Text, Text, Text, Text> { public void reduce(Text key, Iterable<Text> values, Context context) throws IOException , InterruptedException { double sum = 0; int count = 0; for(Text val : values) { String fields[] = val.toString().split(","); sum += Double.parseDouble(fields[0]); count += Integer.parseInt(fields[1]); } context.write(key, new Text(sum + "," + count)); } } 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: AverageByAttribute <int> <out>"); System.exit(2); } //conf.set("key.value.separator.in.input.line", ","); Job job = new Job(conf, "AverageByAttribute"); job.setJarByClass(AverageByAttribute.class); job.setMapperClass(MapClass.class); job.setCombinerClass(CombineClass.class); job.setReducerClass(ReducerClass.class); job.setOutputKeyClass(Text.class); job.setOutputValueClass(Text.class); FileInputFormat.addInputPath(job, new Path(otherArgs[0])); FileOutputFormat.setOutputPath(job, new Path(otherArgs[1])); System.exit(job.waitForCompletion(true)? 0 : 1); } } }
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hdfs://192.168.1.30:9000/data/apat /opt/eclipse/workspace/data/out