(1) protected void setup(Context context)
一般用来加载一些初始化的工作,每个job执行一次
protected void setup(Context context) throws IOException,InterruptedException { blacklist=new TreeSet<String>(); try{ FileReader fileReader=new FileReader(blacklistFileName); BufferedReader bufferedReader=bew BufferedReader(fileReader); String str; while((str=bufferedReader.readLine())!=null){ blacklist.add(str); } } catch(IOException e){ e.printStackTrace(); } }
(2) Protected void map(KEYIN key,VALUEIN value,Context context)
(3) protected void cleanup(Context context)
方法是收尾工作,如关闭文件或者执行map()后的键值分发等,每个job执行一次。比较适合用来算全局最大值之类的任务
@Override
protected void cleanup(Mapper<LongWritable, Text, LongWritable, NullWritable>.Context context)
throws IOException, InterruptedException {
context.write(new LongWritable(max), NullWritable.get());
}
(4) public void run(Context context)