hadoop做的一个简单grep程序，可从文档中提取包含某些字符串的行

复制代码 代码如下:
/*
* 一个简单grep程序，可从文档中提取包含莫些字符串的行
*/

public class grep extends Configured implements Tool{

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;
}