数据清洗：Hadoop计数器的应用以及数据清洗

package com.atguigu.mapreduce.weblog;
import java.io.IOException;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.NullWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Mapper;
public class LogMapper extends Mapper<LongWritable, Text, Text, NullWritable>{
  Text k = new Text();
  @Override
  protected void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException {
   // 1 获取1行数据
   String line = value.toString();
   // 2 解析日志
   boolean result = parseLog(line,context);
   // 3 日志不合法退出
   if (!result) {
     return;
   }
   // 4 设置key
   k.set(line);
   // 5 写出数据
   context.write(k, NullWritable.get());
  }
  // 2 解析日志
  private boolean parseLog(String line, Context context) {
   // 1 截取
   String[] fields = line.split(" ");
   // 2 日志长度大于11的为合法
    if (fields.length > 11) {
     // 系统计数器
     context.getCounter("map", "true").increment(1);
     return true;
   }else {
     context.getCounter("map", "false").increment(1);
     return false;
   }
  }
}

package com.atguigu.mapreduce.weblog;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.NullWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
public class LogDriver {
  public static void main(String[] args) throws Exception {
// 输入输出路径需要根据自己电脑上实际的输入输出路径设置
    args = new String[] { "e:/input/inputlog", "e:/output1" };
   // 1 获取job信息
   Configuration conf = new Configuration();
   Job job = Job.getInstance(conf);
   // 2 加载jar包
   job.setJarByClass(LogDriver.class);
   // 3 关联map
   job.setMapperClass(LogMapper.class);
   // 4 设置最终输出类型
   job.setOutputKeyClass(Text.class);
   job.setOutputValueClass(NullWritable.class);
   // 设置reducetask个数为0
   job.setNumReduceTasks(0);
   // 5 设置输入和输出路径
   FileInputFormat.setInputPaths(job, new Path(args[0]));
   FileOutputFormat.setOutputPath(job, new Path(args[1]));
   // 6 提交
   job.waitForCompletion(true);
  }
}