hadoop实现grep示例分享

 public static  class grepMap extends Mapper<LongWritable, Text, Text,NullWritable>{  public void map(LongWritable line,Text value,Context context) throws IOException, InterruptedException{   //通过Configuration获取参数   String str = context.getConfiguration().get("grep");   if(value.toString().contains(str)){    context.write(value, NullWritable.get());   }  } } @Override public int run(String[] args) throws Exception {  if(args.length!=3){   System.out.println("ERROR");   System.exit(1);  }  Configuration configuration = getConf();  //传递参数  configuration.set("grep", args[2]);  Job job = new Job(configuration,"grep");  job.setJarByClass(grep.class);  job.setMapperClass(grepMap.class);  job.setNumReduceTasks(0);  job.setMapOutputKeyClass(Text.class);  job.setOutputValueClass(NullWritable.class);  Path in = new Path(args[0]);  Path out = new Path(args[1]);  FileSystem fileSystem = out.getFileSystem(configuration);  if(fileSystem.exists(out))   fileSystem.delete(out, true);  FileInputFormat.addInputPath(job, in);  FileOutputFormat.setOutputPath(job, out);  System.exit(job.waitForCompletion(true)?0:1);  return 0; }