Hadoop自定义分组Group

谁借莪１个温暖的怀抱￠ 2022-07-28 08:53 227阅读 0赞

自定义分组MyGroup：  
  
  
主要是继承WritableComparator类，重写compare函数  
  
  
我这里重写的是该源码函数：

/** Compare two WritableComparables.
       *
       * <p> The default implementation uses the natural ordering, calling {@link
       * Comparable#compareTo(Object)}. */
      @SuppressWarnings("unchecked")
      public int compare(WritableComparable a, WritableComparable b) {
        return a.compareTo(b);
      }

原始文件数据：

hadoop  a
    spark   a
    hive    a
    hbase   a
    tachyon a
    storm   a
    redis   a

代码：

import java.io.IOException;
    
    
    import org.apache.hadoop.conf.Configuration;
    import org.apache.hadoop.fs.Path;
    import org.apache.hadoop.io.LongWritable;
    import org.apache.hadoop.io.Text;
    import org.apache.hadoop.io.WritableComparable;
    import org.apache.hadoop.io.WritableComparator;
    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.input.TextInputFormat;
    import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
    import org.apache.hadoop.mapreduce.lib.output.TextOutputFormat;
    import org.apache.hadoop.util.GenericOptionsParser;
    
    
    public class MyGroup {
    	public static void main(String[] args) throws IOException, ClassNotFoundException, InterruptedException {
    		Configuration conf = new Configuration();
    		String[] otherArgs = new GenericOptionsParser(conf, args).getRemainingArgs();
    		if(otherArgs.length!=2){
    			System.err.println("Usage databaseV1 <inputpath> <outputpath>");
    		}
    		
    		Job job = Job.getInstance(conf, MyGroup.class.getSimpleName() + "1");
    		job.setJarByClass(MyGroup.class);
    		job.setMapOutputKeyClass(Text.class);
    		job.setMapOutputValueClass(Text.class);
    		job.setOutputKeyClass(Text.class);
    		job.setOutputValueClass(Text.class);
    		job.setMapperClass(MyMapper1.class);
    		job.setGroupingComparatorClass(MyGroupComparator.class);
    		job.setReducerClass(MyReducer1.class);
    		job.setInputFormatClass(TextInputFormat.class);
    		job.setOutputFormatClass(TextOutputFormat.class);
    		FileInputFormat.addInputPath(job, new Path(otherArgs[0]));
    		FileOutputFormat.setOutputPath(job, new Path(otherArgs[1]));
    		job.waitForCompletion(true);
    	}
    	public static class MyMapper1 extends Mapper<LongWritable, Text, Text, Text>{
    		@Override
    		protected void map(LongWritable key, Text value, Mapper<LongWritable, Text, Text, Text>.Context context)
    				throws IOException, InterruptedException {
    			String[] spl=value.toString().split("\t");
    			context.write(new Text(spl[0].trim()), new Text(spl[1].trim()));
    		}
    	}
    	public static class MyReducer1 extends Reducer<Text, Text, Text, Text>{
    		@Override
    		protected void reduce(Text k2, Iterable<Text> v2s, Reducer<Text, Text, Text, Text>.Context context)
    				throws IOException, InterruptedException {
    			Long count=0L;
    			for (@SuppressWarnings("unused") Text v2 : v2s) {
    				count++;
    				context.write(new Text("in--"+k2), new Text(count.toString()));
    			}
    			context.write(new Text("out--"+k2), new Text(count.toString()));
    		}
    	}
    	public static class MyGroupComparator extends WritableComparator{
    		public MyGroupComparator(){
    			super(Text.class,true);
    		}
    		@SuppressWarnings("rawtypes")
    		public int compare(WritableComparable a, WritableComparable b) {
    			Text p1 = (Text) a;
    			Text p2 = (Text) b;
    			p1.compareTo(p2);
    			return  0;
    		  }
    	}
    }

默认分组结果是这样的：

public static class MyGroupComparator extends WritableComparator{
    		public MyGroupComparator(){
    			super(Text.class,true);
    		}
    		@SuppressWarnings("rawtypes")
    		public int compare(WritableComparable a, WritableComparable b) {
    			Text p1 = (Text) a;
    			Text p2 = (Text) b;
    			return p1.compareTo(p2);
    		  }
    	}

相同Key为一组：

in--hadoop      1
    out--hadoop     1
    in--hbase       1
    out--hbase      1
    in--hive        1
    out--hive       1
    in--redis       1
    out--redis      1
    in--spark       1
    out--spark      1
    in--storm       1
    out--storm      1
    in--tachyon     1
    out--tachyon    1

自定义后：

所有key均为一组：

in--hadoop      1
    in--hbase       2
    in--hive        3
    in--redis       4
    in--spark       5
    in--storm       6
    in--tachyon     7
    out--tachyon    7