hdfs文件操作基本方法(1)

DFSOperater.java

 

import org.apache.hadoop.conf.*;import org.apache.hadoop.fs.*;import org.apache.hadoop.hdfs.*;import org.apache.hadoop.hdfs.protocol.*;import java.util.Date;public class DFSOperater {/** * @param args */public static void main(String[] args) {Configuration conf = new Configuration();try {// Get a list of all the nodes host names in the HDFS clusterFileSystem fs = FileSystem.get(conf);DistributedFileSystem hdfs = (DistributedFileSystem) fs;DatanodeInfo[] dataNodeStats = hdfs.getDataNodeStats();String[] names = new String[dataNodeStats.length];System.out.println("list of all the nodes in HDFS cluster:"); // print// infofor (int i = 0; i < dataNodeStats.length; i++) {names[i] = dataNodeStats[i].getHostName();System.out.println(names[i]); // print info}Path f = new Path("/user/cluster/dfs.txt");// check if a file exists in HDFSboolean isExists = fs.exists(f);System.out.println("The file exists? [" + isExists + "]");// if the file exist, delete itif (isExists) {boolean isDeleted = hdfs.delete(f, false);// fase : not// recursiveif (isDeleted)System.out.println("now delete " + f.getName());}// create and writeSystem.out.println("create and write [" + f.getName()+ "] to hdfs:");FSDataOutputStream os = fs.create(f, true, 0);for (int i = 0; i < 10; i++) {os.writeChars("test hdfs ");}os.writeChars("/n");os.close();// get the locations of a file in HDFSSystem.out.println("locations of file in HDFS:");FileStatus filestatus = fs.getFileStatus(f);BlockLocation[] blkLocations = fs.getFileBlockLocations(filestatus,0, filestatus.getLen());int blkCount = blkLocations.length;for (int i = 0; i < blkCount; i++) {String[] hosts = blkLocations[i].getHosts();// Do sth with the block hostsSystem.out.println(hosts);}// get HDFS file last modification timelong modificationTime = filestatus.getModificationTime(); // measured// in// milliseconds// since// the// epochDate d = new Date(modificationTime);System.out.println(d);// reading from HDFSSystem.out.println("read [" + f.getName() + "] from hdfs:");FSDataInputStream dis = fs.open(f);System.out.println(dis.readUTF());dis.close();} catch (Exception e) {// TODO: handle exceptione.printStackTrace();}}}