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);

}

}