GenericWritable

package com.test;

import java.io.IOException;
import java.util.Iterator;
import java.util.StringTokenizer;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.conf.Configured;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.GenericWritable;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.io.Writable;
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.KeyValueTextInputFormat;
import org.apache.hadoop.mapreduce.lib.input.MultipleInputs;
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.Tool;
import org.apache.hadoop.util.ToolRunner;

/**
 * 业务场景：
 * 含有两个文件，两个文件中单词之间的分隔方式不一样，但是统计出单词在两个文件中公共出现的次数
 *
 * 文件来源1，逗号分隔text1.txt
 *  hello,what
 *  you,haha
 * 文件来源2，制表符分隔text2.txt
 * girl boy
 * father mother
 */
public class WordCountGenericWritable extends Configured implements Tool {
 
 public static class Map1 extends Mapper<LongWritable, Text, Text, MyGenericWritable> {
  public void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException {
   String line = value.toString();
   
   StringTokenizer st = new StringTokenizer(line, ",");
   while(st.hasMoreElements()) {
    context.write(new Text(st.nextElement().toString()), new MyGenericWritable(new LongWritable(1)));
   }
  }
 }
 
 public static class Map2 extends Mapper<Text, Text, Text, MyGenericWritable> {
  public void map(Text key, Text value, Context context) throws IOException, InterruptedException {
   context.write(key, new MyGenericWritable(new Text("1")));
   context.write(value, new MyGenericWritable(new Text("1")));
  }
 }
 
 public static class Reduce extends Reducer<Text, MyGenericWritable, Text, IntWritable> {
  public void reduce(Text key, Iterable<MyGenericWritable> values, Context context) throws IOException, InterruptedException {
   int count = 0;
   Iterator<MyGenericWritable> it = values.iterator();
   while(it.hasNext()) {
    MyGenericWritable myGw = it.next();
    Writable value = myGw.get();
    if(value instanceof LongWritable) {
     count = count + Long.valueOf(((LongWritable)value).get()).intValue();
    }
    if(value instanceof Text) {
     count = count + Long.valueOf(((Text)value).toString()).intValue();
    }
   }
   context.write(key, new IntWritable(count));
  }
 }
 
 public int run(String[] args) throws IOException, InterruptedException, ClassNotFoundException {
  Configuration conf = this.getConf();
  Job job = new Job(conf);
  job.setJobName(WordCountGenericWritable.class.getSimpleName());
  job.setJarByClass(WordCountGenericWritable.class);
  
  MultipleInputs.addInputPath(job, new Path("hdfs://grid131:9000/text1.txt"), TextInputFormat.class, Map1.class);
  MultipleInputs.addInputPath(job, new Path("hdfs://grid131:9000/text2.txt"), KeyValueTextInputFormat.class, Map2.class);
  
  FileOutputFormat.setOutputPath(job, new Path(args[1]));
  job.setReducerClass(Reduce.class);
  
  job.setOutputFormatClass(TextOutputFormat.class);
  
  //当map的输出类型和reduce的输出类型不一致的时候，需要单独设置map输出类型
  job.setMapOutputKeyClass(Text.class);
  job.setMapOutputValueClass(MyGenericWritable.class);
  
  job.setOutputKeyClass(Text.class);
  job.setOutputValueClass(IntWritable.class);
  
  job.waitForCompletion(true);
  
  return job.isSuccessful()?0:1;
 }
 
 public static void main(String[] args) throws Exception {
  int exit = ToolRunner.run(new WordCount(), args);
  System.exit(exit);
 }
 
}

class MyGenericWritable extends GenericWritable {

 public MyGenericWritable() {
  
 }
 
 public MyGenericWritable(LongWritable longWritable) {
  super.set(longWritable);
 }
 
 public MyGenericWritable(Text text) {
  super.set(text);
 }
 
 @Override
 protected Class<? extends Writable>[] getTypes() {
  return new Class[]{LongWritable.class, Text.class};
 }
 
}