MapReduce求最大值最小值问题

import java.io.File;

import java.io.IOException;

 

import org.apache.hadoop.conf.Configuration;

import org.apache.hadoop.fs.Path;

import org.apache.hadoop.io.Text;

import org.apache.hadoop.mapred.JobConf;

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.output.FileOutputFormat;

 

public class GetMinMaxKeyMapReduce {

     

    public static class GetMinMaxKeyMap extends Mapper<Object, Text, Text,Text> {

        private Text min = new Text();

        private Text max = new Text();

        private Long i = new Long(0);

        public void map(Object key, Text value, Context context) throws IOException, InterruptedException {

            String[] strs = value.toString().split("\t");

            if (strs!=null && strs.length>5 &&strs[3].length() > 20 && strs[3].indexOf(" ") == -1 && strs[3].indexOf("=") == -1) {

                if(i==0){

                    min= new Text(strs[3]);

                    max= new Text(strs[3]);

                }

                if(strs[3].compareTo(min.toString())<0){

                    min=new Text(strs[3]);

                }

                if(strs[3].compareTo(max.toString())>0){

                    max=new Text(strs[3]);

                }

                i++;

            }

        }

         

        @Override

        protected void cleanup(Context context) throws IOException, InterruptedException {

            context.write(new Text("min"), min);

            context.write(new Text("max"), max);

        }

    }

 

    public static class GetMinMaxKeyReducer extends Reducer<Text, Text, Text, Text> {

        public void reduce(Text key, Iterable<Text> values, Context context) throws IOException, InterruptedException {

            String result ="";

            for (Text value : values) {

                if(result.equals("")){

                    result = value.toString();

                }

                if (("min").equals(key.toString())) {

                    if(value.toString().compareTo(result)<0){

                        result=value.toString();

                    }

                } else if (("max").equals(key.toString())) {

                    if(value.toString().compareTo(result)>0){

                        result=value.toString();

                    }

                } else {

                    System.err.println("未知reduce 输入key:" + key.toString());

                }

            }

            context.write(key, new Text(result));

        }

    }

 

    public static void main(String[] args) throws Exception {

        File jarFile = EJob.createTempJar("bin");

        ClassLoader classLoader = EJob.getClassLoader();

        Thread.currentThread().setContextClassLoader(classLoader);

         

        //Hadoop 运行环境

        Configuration conf = new Configuration();

        conf.set("mapred.job.tracker", "bfdbjc1:12001");;

         

        //任务参数设置

        Job job = new Job(conf, "GetMinMaxKey");

 

        job.setJarByClass(GetMinMaxKeyMapReduce.class);

        job.setMapperClass(GetMinMaxKeyMap.class);

        job.setReducerClass(GetMinMaxKeyReducer.class);

 

        job.setMapOutputKeyClass(Text.class);

        job.setMapOutputValueClass(Text.class);

 

        job.setOutputKeyClass(Text.class);

        job.setOutputValueClass(Text.class);

         

        FileInputFormat.addInputPath(job, new Path("hdfs://bfdbjc1:12000/user/work/tables2/raw_kafka/l_date=2013-09-15"));

        FileOutputFormat.setOutputPath(job, new Path("hdfs://bfdbjc1:12000/user/work/output/minmaxkey/"));

         

        //Eclipse 本地提交

        ((JobConf) job.getConfiguration()).setJar(jarFile.toString());

         

        //等待任务运行完成

        System.exit(job.waitForCompletion(true) ? 0 : 1);

    }

}