hadoop案例:KeyValueTextInputFormat

青旅半醒 2022-11-21 14:54 141阅读 0赞

### 文章目录 ###

*   *  输入数据
     *  期望结果
     *  需求分析
     *  Mapper类
     *  Reducer类
     *  Driver类

## 输入数据 ##

文件 value.txt

banzhang ni hao
    xihuan hadoop banzhang
    banzhang ni hao
    xihuan hadoop banzhang

## 期望结果 ##

banzhang	2
    xihuan	2

## 需求分析 ##

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQzNjc0MzYw_size_16_color_FFFFFF_t_70_pic_center]

## Mapper类 ##

package com.mr.keyvalue;
    
    import org.apache.hadoop.io.IntWritable;
    import org.apache.hadoop.io.Text;
    import org.apache.hadoop.mapreduce.Mapper;
    
    import java.io.IOException;
    
    public class KVTextMapper extends Mapper<Text, Text,Text, IntWritable> { 
    
        IntWritable v = new IntWritable(1);
        @Override
        protected void map(Text key, Text value, Context context) throws IOException, InterruptedException { 
            //
    
            context.write(key,v);
    
            }
    
    
        }

## Reducer类 ##

## Driver类 ##

package com.mr.keyvalue;
    
    import org.apache.hadoop.io.IntWritable;
    import org.apache.hadoop.io.Text;
    import org.apache.hadoop.mapreduce.Reducer;
    
    import java.io.IOException;
    
    public class KVTextReducer extends Reducer<Text, IntWritable,Text,IntWritable> { 
        IntWritable v = new 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();
    
            }
            v.set(sum);
            //
    
            context.write(key,v);
        }
    }

执行结果  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQzNjc0MzYw_size_16_color_FFFFFF_t_70_pic_center 1]

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQzNjc0MzYw_size_16_color_FFFFFF_t_70_pic_center]: /images/20221120/1c76fdf34cf4482c8b84987f3d833af4.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQzNjc0MzYw_size_16_color_FFFFFF_t_70_pic_center 1]: /images/20221120/abffcd8b94e4431185b114903c05c899.png