hadoop Java接口 文件操作类

前几天看到篇文章，是用java的API操作HDFS的文件系统。那篇文章单独介绍了每个api的使用，为了以后方便使用，我写成了一个类，现分享给大家。

文件操作类：

比较简单，大家也可以自己完善。

import java.io.IOException;import java.util.ArrayList;import java.util.List;import org.apache.hadoop.conf.Configuration;import org.apache.hadoop.fs.BlockLocation;import org.apache.hadoop.fs.FSDataInputStream;import org.apache.hadoop.fs.FSDataOutputStream;import org.apache.hadoop.fs.FileStatus;import org.apache.hadoop.fs.FileSystem;import org.apache.hadoop.fs.Path;import org.apache.hadoop.hdfs.DistributedFileSystem;import org.apache.hadoop.hdfs.protocol.DatanodeInfo;import org.apache.hadoop.io.IOUtils;public class HDFS_File { //read the file from HDFS public void ReadFile(Configuration conf, String FileName){ try{ FileSystem hdfs = FileSystem.get(conf); FSDataInputStream dis = hdfs.open(new Path(FileName)); IOUtils.copyBytes(dis, System.out, 4096, false); dis.close(); }catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } //copy the file from HDFS to local public void GetFile(Configuration conf, String srcFile, String dstFile){ try { FileSystem hdfs = FileSystem.get(conf); Path srcPath = new Path(srcFile); Path dstPath = new Path(dstFile); hdfs.copyToLocalFile(true,srcPath, dstPath); }catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } //copy the local file to HDFS public void PutFile(Configuration conf, String srcFile, String dstFile){ try { FileSystem hdfs = FileSystem.get(conf); Path srcPath = new Path(srcFile); Path dstPath = new Path(dstFile); hdfs.copyFromLocalFile(srcPath, dstPath); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } //create the new file public FSDataOutputStream CreateFile(Configuration conf, String FileName){ try { Configuration config = new Configuration(); FileSystem hdfs = FileSystem.get(config); Path path = new Path(FileName); FSDataOutputStream outputStream = hdfs.create(path); return outputStream; } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } return null; } //rename the file name public boolean ReNameFile(Configuration conf, String srcName, String dstName){ try { Configuration config = new Configuration(); FileSystem hdfs = FileSystem.get(config); Path fromPath = new Path(srcName); Path toPath = new Path(dstName); boolean isRenamed = hdfs.rename(fromPath, toPath); return isRenamed; }catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } return false; } //delete the file // tyep = true, delete the directory // type = false, delece the file public boolean DelFile(Configuration conf, String FileName, boolean type){ try { Configuration config = new Configuration(); FileSystem hdfs = FileSystem.get(config); Path path = new Path(FileName); boolean isDeleted = hdfs.delete(path, type); return isDeleted; }catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } return false; } //Get HDFS file last modification time public long GetFileModTime(Configuration conf, String FileName){ try{ Configuration config = new Configuration(); FileSystem hdfs = FileSystem.get(config); Path path = new Path(FileName); FileStatus fileStatus = hdfs.getFileStatus(path); long modificationTime = fileStatus.getModificationTime(); return modificationTime; }catch(IOException e){ e.printStackTrace(); } return 0; } //checke if a file exists in HDFS public boolean CheckFileExist(Configuration conf, String FileName){ try{ Configuration config = new Configuration(); FileSystem hdfs = FileSystem.get(config); Path path = new Path(FileName); boolean isExists = hdfs.exists(path); return isExists; }catch(IOException e){ e.printStackTrace(); } return false; } //Get the locations of a file in the HDFS cluster public List<String []> GetFileBolckHost(Configuration conf, String FileName){ try{ List<String []> list = new ArrayList<String []>(); Configuration config = new Configuration(); FileSystem hdfs = FileSystem.get(config); Path path = new Path(FileName); FileStatus fileStatus = hdfs.getFileStatus(path); BlockLocation[] blkLocations = hdfs.getFileBlockLocations(fileStatus, 0, fileStatus.getLen()); int blkCount = blkLocations.length; for (int i=0; i < blkCount; i++) { String[] hosts = blkLocations[i].getHosts(); list.add(hosts); } return list; }catch(IOException e){ e.printStackTrace(); } return null; } //Get a list of all the nodes host names in the HDFS cluster public String[] GetAllNodeName(Configuration conf){ try{ Configuration config = new Configuration(); FileSystem fs = FileSystem.get(config); DistributedFileSystem hdfs = (DistributedFileSystem) fs; DatanodeInfo[] dataNodeStats = hdfs.getDataNodeStats(); String[] names = new String[dataNodeStats.length]; for (int i = 0; i < dataNodeStats.length; i++) { names[i] = dataNodeStats[i].getHostName(); } return names; }catch(IOException e){ e.printStackTrace(); } return null; }}

自己写的测试程序：

import java.io.IOException;import java.util.Date;import java.util.List;import org.apache.hadoop.conf.Configuration;import org.apache.hadoop.fs.FSDataOutputStream;public class File_Operation { public static void main(String args[]){ Configuration conf = new Configuration(); HDFS_File file = new HDFS_File(); //print all the node name String[] host_name = file.GetAllNodeName(conf); for (int i = 0; i<host_name.length; i++) { System.out.println("the host name:"+host_name); } //create the file String File_Name = "my_test"; FSDataOutputStream fs = file.CreateFile(conf, File_Name); if (fs != null){ try { fs.close(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } System.out.println(File_Name+"create OK"); } else{ System.out.println(File_Name+"create fail"); } //check the file exists if (file.CheckFileExist(conf, File_Name) == true){ System.out.println(File_Name+"the file exists"); } else{ System.out.println(File_Name+"the file not exists"); } //delete the file if (file.DelFile(conf, File_Name, false) == true){ System.out.println(File_Name+"the file delete"); } else{ System.out.println(File_Name+"the file not delete"); } //copy the file to HDFS String srcFile = "/home/jackydai/my"; String ToFile = "/home/jackydai/my11"; String dstFile = "/user/jackydai/my"; file.PutFile(conf, srcFile, dstFile); System.out.println("copy file ok!"); //check the file last modfiy time long mod_time = file.GetFileModTime(conf, dstFile); Date d = new Date(mod_time); System.out.println("the modefile time"+d); //get the locations of a file in HDFS List<String []> list = file.GetFileBolckHost(conf, dstFile); for (int i = 0; i < list.size(); i++){ for(int j = 0; j < list.get(i).length; j++){ System.out.println("the bolck host name:"+list.get(i)[j]); } } System.out.println("host name over!"); //read the file file.ReadFile(conf, dstFile); System.out.println("read over!"); //copy the file to local file.GetFile(conf, dstFile, ToFile); System.out.println("copy ok"); }}