Hadoop FileSystem API读取数据实例简单注释

import java.io.InputStream;
import java.net.URI;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IOUtils;
// vv FileSystemCat
public class FileSystemCat {
  public static void main(String[] args) throws Exception {
    String uri = args[0];//uri 被赋值为第一个参数
    Configuration conf = new Configuration();//新的接口
    FileSystem fs = FileSystem.get(URI.create(uri),conf);//得到FileSystem实例
    InputStream in = null;
    try {
      in = fs.open(new Path(uri));//打开 得到的是FSInputDataStream对象
      IOUtils.copyBytes(in, System.out, 4096, false);//显示
    } finally {
      IOUtils.closeStream(in);
    }
  }
}