Deprecated API Versus New API

Seq No	Deprecated API	NEW API
1	Release 0.20	Release 1.X and 2.X
2	Interfaces (means you can add a method with default implementation to an abstract class without breaking old implementations of class	Abstract classes For Example Mapper and Reducer interfaces in Old API are abstract classes in new API
3	Package org.apache.hadoop.mapred	org.apache.hadoop.mapreduce
4	JobConf,the OutputCollector and the Reporter	Context Object  (allows the user code to communicate with MapReduce System)
5	Both API’s, Key-Value record pairs are pushed to mapper and reducer	In addition execution flow can be controlled by run() method
6	Job Control by JobClient class	Job class
7	Output file are named as Part-nnnnn	Part-m-nnnnn( mapper) , part-r-nnnnn(reducer)
8	No provision	User overridable methods  are declared to throw java.lang.InteruptedException
9	reduce() method passes values to java.lang.Iterator	java.lang.Iterable (making easier to iterate over the values using Java’s for-each loop construct for(VALUEIN value:values){………}
10	Configuration c = new Configuration; Job j = new Job (c,”TEST JOB”);	jobConf conf = new jobConf(); conf.setJarByClass();
11	System.exit(job.waitforcompletion(true)?0:1);	jobClient.runjob(conf);

Deprecated API Sample :


Public class OldMaxTemp {
    static class OldMaxTempMapper extends MapReduceBase
        implements Mapper<LongWritable,Text,Text,IntWritable> {
        private static final int MISSING = 9999;
       
        @Override
        public void map(LongWritable key,Text Value,
            OutputCollector<Text,IntWritable> output,Reporter reporter)
            throws IOException {
           
            String line = value.toString();
            String year = line.substring(15,19);
            int airTemp;
            if (line.charAt(87) == '+')
                { //parse Int doesn't like leading plus signs
                airTemp = Integer.parseInt(line.substring(88,92));
                } else
                {
                airTemp = Integer.parseInt(line.substring(87,92));
                }
            String quality = line.substing(92,93);
            if (airTemp != MISSING && quality.matches("[01459]")) {
                output.collect(new Text(year) , new IntWritable(airTemp));
                }
            }
        }
       
       
static class oldMaxTempReducer extends MapReduceBase
    implements Reducer<Text,IntWritable,Text,IntWritable>{
   
    @override
    public void reduce(Text Key,Iterator<IntWritable> values,
        OutputCollector<Text , IntWritable> output,Reporter reporter)
        throws IOException {
        int maxValue = Integer.MIN_VALUE;
        while (values.hasNext()){
            maxValue =Math.max(maxValue,values.next().get());
        }
        output.collect(key, new IntWritable(maxValue));
    }
   
}

public static void main(Sting[] args throws IOException {
    if (args.length !=2) {
    System.err.println("Usage:Old Max Temp <input> <output>");
    System.exit(-1);
    }
    JobConf conf = new JobConf(OldMaxTemp.class);
    conf.setJobName("MAX TEMP");
   
    FileInputFormat.addInputPath(conf,new Path(args[0]));
    FileOutputFormat.setOutputPath(conf,new Path(args[1]));
   
    conf.setMapperClass(OldMaxTempMapper.class);
    conf.setReducerClass(OldMaxTempReducer.class);
   
    conf.setOutputKeyClass(Text.class);
    conf.setOutputValueClass(IntWritable.class);
   
    JobClient.runJob(conf);
    }
}

New API Sample:

 import java.io.IOException;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Mapper;
import org.apache.hadoop.mapreduce.Reducer;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;


public class MaxTempMapper
    extends Mapper<LongWritable,Text,Text,IntWritable> {
    private static final int MISSING = 9999;
   
    @Override
    public void map(LongWritable key,Text value,Context context)
        throws IOException,InterruptedException {
        String line = value.toString();
        String year = line.substring(15,19);
        int airTemp;
        if (line.cahrAt(87) == '+' {
        //parseInt doesn't like leading plus sign
           airTemp = Integer.parseInt(line.substring(88,92);
        }else {
           airTemp = Integer.parseInt(line.substring(87,92);
        }
        String quality = line.substing(92,93);
        if (airTemp != MISSING && quality.matches("[01459]") {
            context.write(new Text(year),new IntWritable(airTemp));
        }
    }
}

publice class MaxTempReducer
    extends Reducer<Text,IntWritable,Text,IntWritable>{
   
    @override
    public void reduce(Text key,Iterable<IntWritable> values,Context context)
        throws IOException, InterruptedException {
      
        int maxValue = Integer.MIN_VALUE;
        for (Intwritable value :values) {
            maxValue = Math.max(maxValue,value.get());
            }
        context.write(key , new IntWritable(maxValue));
        }
    }
   
public class MaxTemp {
    public static void main(String[] args) throws Exception {
        if (args.length != 2) {
            System.err.println("Usage :Max Temp <input> <output>");
            System.exit(-1);
            }
          
        Job job = new Job();
        job.setJarByClass(MaxTemp.class);
        job.setJobName("MAX TEMP");
      
        FileInputFormat.addInputPath(job,new Path(args[0]));
        FileOutputFormat.setOutputPath(job,new Path(args[1]);
      
        job.setMapperClass(MaxTempMapper.class);
        job.setReducerClass(MaxTempReducer.class);
      
        job.setOutputKeyClass(Text.class);
        job.setOutputValueClass(IntWritable.class);
      
        System.exit(job.waitForCompletion(true) ? 0:1);
    }
}