package
 
 cjkjcn.demo.hadoop.hdfs;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.LinkedList;
import java.util.List;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FSDataInputStream;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
/**
 *
 * @author junhong
 *
 * 2017年5月18日
 */
public class HDFSDao {
     private static Configuration conf = new Configuration();
     private FileSystem hdfs;
     final static String ROOT_PATH = "/user";
     public HDFSDao() {
           conf.addResource("hdfs-site.xml");
           conf.addResource("core-site.xml");
           try {
                hdfs = FileSystem.get(conf); // 初始化hdfs
           } catch (IOException e) {
                e.printStackTrace();
           }
           System.out.println("param size=" + conf.size());
     }
     /**
      * 掃描測試文件是否存在
      */
     public void scanFiles() {
           try {
                Path path = new Path(ROOT_PATH);
                System.out.println(hdfs.exists(path));
           } catch (IOException e) {
                e.printStackTrace();
           }
     }
     /**
      * 按行讀取文本文件
      * @param file
      * @return
      */
     public List<String> lines(String file) {
           List<String> list = new LinkedList<>();
           Path f = new Path(file);
           try {
                FSDataInputStream input = hdfs.open(f);
                InputStreamReader inr = new InputStreamReader(input);
                BufferedReader read = new BufferedReader(inr);
                String line;
                while ((line = read.readLine()) != null) {
                     list.add(line);
                }
           } catch (IOException e) {
                e.printStackTrace();
           }
           return list;
     }
}

HDFS Java Client對hdfs文件增刪查改