hadoop输出控制，输出到指定文件中

最近在研究将hadoop输出内容放到指定的文件夹中，

（未完待续）

以wordcount内容为例子：

public class wordcount {
    public static class TokenizerMapper extends
            Mapper<Object, Text, Text, IntWritable>
    {
        private final static IntWritable one = new IntWritable(1);
        private Text word = new Text();

        public void map(Object key, Text value, Context context)
                throws IOException, InterruptedException {
            StringTokenizer itr = new StringTokenizer(value.toString());
            while (itr.hasMoreTokens()) {
                word.set(itr.nextToken());
                context.write(word, one);
            }
        }
    }
   
   
    public static class IntSumReducer extends
            Reducer<Text, IntWritable, Text, IntWritable> {
        private IntWritable result = new IntWritable();
       
        private MultipleOutputs<Text, IntWritable> mo;
       
        public void reduce(Text key, Iterable<IntWritable> values,
                Context context) throws IOException, InterruptedException {
           
            int sum = 0;
            for (IntWritable val : values) {
                sum += val.get();
            }
            result.set(sum);
            context.write(key, result);
           

            mo = new MultipleOutputs<Text, IntWritable>(context);//context和MultipleOutputs是独立的，都进行了写功能，互不干扰
            //MultipleOutputs的write写到多个文件，但是文件之间不能覆盖
            Text kw= new Text("this a test!sum is:");
            IntWritable content= new IntWritable(sum);
            
            mo.write(kw, content, key.toString());//success，输出内容到输出目录out下的key.toString()文件中去。其内容全部分开，wordcount自身的context输出文件中包含全部内容，而MultipleOutputs在这里将他们分开写到不同的文件里面去。
            //mo.write(key, result, "error"+key.toString());//success
            //mo.write(key, result, "all");//testall.jar 有问题，因为all-r-00000生成一次后，不能覆盖
           
            //mo.write(key, result, null);//wrong!no file to write
            //mo.write(key, result, "/user/test");//unsuccess
            //mo.write(null, key, result, key.toString());

            //mo.write(key, result, "all");//unsuccess
            //mo.write(key.toString(), key, result);//unsuccess
            mo.close();
        }
    }
   
    public static void main(String[] args) throws Exception {
     Configuration conf = new Configuration();
   
     String[] otherArgs = new GenericOptionsParser(conf, args).getRemainingArgs();
     if (otherArgs.length != 2) {
     System.err.println("Usage: wordcount <in> <out>");
     System.exit(2);
     }
    
    
     Job job = new Job(conf, "word count");
     job.setJarByClass(wordcount.class);
     job.setMapperClass(TokenizerMapper.class);
     job.setCombinerClass(IntSumReducer.class);
     job.setReducerClass(IntSumReducer.class);
     job.setOutputKeyClass(Text.class);
     job.setOutputValueClass(IntWritable.class);
//     job.setOutputFormatClass(testOutputFormat.class)
    
     FileInputFormat.addInputPath(job, new Path(otherArgs[0]));
     FileOutputFormat.setOutputPath(job, new Path(otherArgs[1]));
    
     System.exit(job.waitForCompletion(true) ? 0 : 1);
    }
}