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  • 天津东软实训第八天------倒排索引

    倒排索引流程图:(有三个文件,里边有三句话,分别统计每个单词在每个文件中出现的次数)

    package com.young;
    
    import org.apache.commons.lang.StringUtils;
    import org.apache.hadoop.conf.Configuration;
    import org.apache.hadoop.fs.Path;
    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.lib.input.FileInputFormat;
    import org.apache.hadoop.mapreduce.lib.input.FileSplit;
    import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
    import java.io.IOException;
    public class App 
    {
        public static class MyMap extends Mapper<LongWritable,Text,Text,IntWritable>{
            @Override
            protected void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException {
                String line = value.toString();//按行读取文件
                String[] fields = StringUtils.split(line," ");//按空格进行分片
                FileSplit fileSplit = (FileSplit) context.getInputSplit();
                String fileName = fileSplit.getPath().getName();//获取文件名
                for(String field:fields)
                {
                   context.write(new Text(field+"-->" + fileName),new IntWritable(1));
                }
            }
        }
        public static class MyReduce extends Reducer<Text,IntWritable,Text,IntWritable>{
            @Override
            protected void reduce(Text key, Iterable<IntWritable> values, Context context) throws IOException, InterruptedException {
                int sum = 0;
                for(IntWritable value:values)
                {
                    sum+=value.get();//统计每个key值对应的value值
                }
                context.write(key,new IntWritable(sum));
            }
        }
        public static void main(String[] args) throws IOException, ClassNotFoundException, InterruptedException {
            Configuration conf = new Configuration();
            conf.set("fs.defaultFS","hdfs://192.168.131.142:9000");
            Job job  = Job.getInstance(conf);
            job.setJarByClass(App.class);
            job.setMapperClass(MyMap.class);
            job.setMapOutputKeyClass(Text.class);
            job.setMapOutputValueClass(IntWritable.class);
            job.setReducerClass(MyReduce.class);
            job.setMapOutputKeyClass(Text.class);
            job.setMapOutputValueClass(IntWritable.class);
            FileInputFormat.addInputPath(job,new Path("/idea/a.txt"));//读取HDFS上idea目录下的a.txt文件
            FileInputFormat.addInputPath(job,new Path("/idea/b.txt"));
            FileInputFormat.addInputPath(job,new Path("/idea/c.txt"));
            FileOutputFormat.setOutputPath(job,new Path("/idea/out3"));//将结果保存在idea目录下的out3目录下
            job.waitForCompletion(true);
        }
    
    }
    

      

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  • 原文地址:https://www.cnblogs.com/huyangyang/p/9325283.html
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