package jishuqi;

import java.io.IOException;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.NullWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Counter;
import org.apache
 
.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.Mapper;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
/*
 * 統計不合法的資料條數   通過全域性計數器  全域性計數器都在控制檯輸出
 * ------用於統計資料中特定的資訊
 */
public class MissFileds {
    static class MyMapper extends Mapper<LongWritable, Text, NullWritable, NullWritable>{
        /**
         * LongWritable key,偏移量
         *  Text value,一行內容
            Context context  上下文物件   傳輸   job執行過程中上文傳引數
         */
 

        @Override
        protected void map(LongWritable key, Text value,
                Mapper<LongWritable, Text, NullWritable, NullWritable>.Context context)
                throws IOException, InterruptedException {
            //取出你每一條資料
            String[] split = value.toString().split
 
(",");
            //進行判斷    如果長度為3  證明  資料完美   否則資料殘缺
            if(split.length<3){
                //將殘缺的資料記錄在全域性計數器中
                //取出全域性計數器
                Counter counter = context.getCounter(MissCounter.Miss_Field_Lines);
                /*
                   Increment this counter by the given value
                   * @param incr the value to increase this counter by
                   */
                 //void increment(long incr);  引數代表需要增加的值  類似於   +=incr
                counter.increment(1L);
            }
        }

    }

    //Driver
    public static void main(String[] args) throws IOException, ClassNotFoundException, InterruptedException {
        System.setProperty("HADOOP_USER_NAME", "hadoop");
        Configuration conf=new Configuration();
        conf.set("fs.defaultFS", "hdfs://hadoop02:9000");

        Job job=Job.getInstance(conf);

        job.setJarByClass(MissFileds.class);
        //只需一個mapper就可以了
        job.setMapperClass(MyMapper.class);

        //設定map的輸出
        job.setOutputKeyClass(NullWritable.class);  //沒有資料輸出
        job.setOutputValueClass(NullWritable.class);

        //如果不需要reducetask   這裡請設定為0   否則預設執行一個reducetask任務
        job.setNumReduceTasks(0);
        //可以指定多個輸入路徑
        FileInputFormat.setInputPaths(job, new Path("/friendout_01"));
        //輸出路徑需要嗎？    不設定  報錯Output directory not set.
        FileOutputFormat.setOutputPath(job, new Path("/counter_out01"));
        job.waitForCompletion(true);
    }
}

自定義一個列舉類

package jishuqi;
/**
 * 列舉類定義全域性變數
 * @author Administrator
 */
public enum MissCounter {
    Miss_Field_Lines
}