How to customize Partition by mapreducez in hadoop

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Package hello_hadoop;import java.io.IOException;import org.apache.hadoop.conf.Configuration;import org.apache.hadoop.fs.Path;import org.apache.hadoop.io.DoubleWritable;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.Partitioner;import org.apache.hadoop.mapreduce.Reducer;import org.apache.hadoop.mapreduce.lib.input.FileInputFormat Import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;public class AutoParitionner {public static void main (String [] args) throws IOException, ClassNotFoundException, InterruptedException {if (args.roomthkeeper 2) {System.err.println ("Usage: hadoop jar xxx.jar"); System.exit (1);} Configuration conf = new Configuration () Job job = Job.getInstance (conf, "avg of grades"); job.setJarByClass (AutoParitionner.class); job.setMapperClass (PartitionInputClass.class); job.setReducerClass (PartitionOutputClass.class); job.setMapOutputKeyClass (Text.class); job.setMapOutputValueClass (DoubleWritable.class); job.setOutputKeyClass (Text.class) Job.setOutputValueClass (DoubleWritable.class); / / the class that declares the custom partition is declared below: job.setPartitionerClass (MyPartitioner.class); job.setNumReduceTasks (2); FileInputFormat.addInputPath (job, new Path (args [0])); FileOutputFormat.setOutputPath (job, new Path (args [1])) System.exit (job.waitForCompletion (true)? 0:1);} class PartitionInputClass extends Mapper {@ Override protected void map (LongWritable key, Text value, Mapper.Context context) throws IOException, InterruptedException {String line = value.toString () If (line.length () > 0) {String [] array = line.split ("\ t"); if (array.length==2) {String name=array [0]; int grade = Integer.parseInt (array [1]) Context.write (new Text (name), new DoubleWritable (grade)) } class PartitionOutputClass extends Reducer {@ Override protected void reduce (Text text, Iterable iterable, Reducer.Context context) throws IOException, InterruptedException {int sum = 0; int cnt= 0 For (DoubleWritable iw: iterable) {sum+=iw.get (); cnt++;} context.write (text, new DoubleWritable (sum/cnt)) }} / / the class / / Partitioner Text,DoubleWirtable of the custom partition is key,valueclass MyPartitioner extends Partitioner {@ Override public int getPartition (Text text, DoubleWritable value, int numofreuceTask) {String name = text.toString () of the map result, respectively. If (name.equals ("wd") | | name.equals ("wzf") | | name.equals ("xzh") | | name.equals ("zz") {return 0;} else return 1;}} these are all the contents of the article "how to customize partitions in hadoop". Thank you for reading! I believe we all have a certain understanding, hope to share the content to help you, if you want to learn more knowledge, welcome to follow the industry information channel!