MapReduce编程实例之自定义分区
任务描述： 一组数据，按照年份的不同将其分别存放在不同的文件里 example Data： 2013 1 2013 5 2014 5 2014 8 2015 9 2015 4 Code： package mrTest; import java.io.IOException; import java.util.StringTokenizer; import org.apache.hadoop.fs.Path; import org.apache.hadoop.io.IntWritable; 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 zidingyiPartition { public static class myPartition extends Partitioner<LongWritable, LongWritable>{ public int getPartition(LongWritable key, LongWritable value, int numTaskReduces) { // TODO Auto-generated method stub if(key.get()==2013){ return 0; }else if(key.get()==2014){ return 1; }else{ return 2; } } } public static class Map extends Mapper<Object, Text, LongWritable,LongWritable>{ public void map(Object key, Text value, Context context) throws IOException, InterruptedException{ String[] line = value.toString().split("\t"); context.write( new LongWritable(Integer.parseInt(line[0])) , new LongWritable(Integer.parseInt(line[1])) ); } } public static class Reduce extends Reducer<LongWritable, LongWritable, LongWritable, LongWritable>{ public void reduce(LongWritable key, Iterable<LongWritable> values, Context context) throws IOException, InterruptedException{ for (LongWritable longWritable : values) { context.write(key, longWritable); } } } public static void main(String[] args) throws IOException, ClassNotFoundException, InterruptedException { // TODO Auto-generated method stub Job job = new Job(); job.setJarByClass(zidingyiPartition.class); // 1 FileInputFormat.addInputPath(job, new Path(args[0])); // 2 job.setMapperClass(Map.class); job.setMapOutputKeyClass(LongWritable.class); job.setMapOutputValueClass(LongWritable.class); // 3 job.setPartitionerClass(myPartition.class); // 4 // 5 job.setNumReduceTasks(3); // 6 job.setReducerClass(Reduce.class); job.setOutputKeyClass(LongWritable.class); job.setOutputValueClass(LongWritable.class); // 7 FileOutputFormat.setOutputPath(job, new Path(args[1])); // 8 System.exit(job.waitForCompletion(true)? 0 : 1); } } 结果展示：
