Shulou(Shulou.com)06/03 Report--

Required jar package

I. URL API operation mode

Import java.io.InputStream;import java.net.URL;import org.apache.hadoop.fs.FsUrlStreamHandlerFactory;import org.apache.hadoop.io.IOUtils;import org.junit.Test;public class HDFSUrlTest {/ * HDFS URL API operation mode * there is no need to read core-site.xml and hdfs-site.xml configuration files * / / Let the JAVA program recognize HDFS's URL static {URL.setURLStreamHandlerFactory (new FsUrlStreamHandlerFactory ()) } / / View the file content @ Test public void testRead () throws Exception {InputStream in = null; / / file path String fileUrl = "hdfs://hadoop-master.dragon.org:9000/opt/data/test/01.data"; try {/ / get the file input stream in = new URL (fileUrl) .openStream () / / read out the contents of the file and print the console IOUtils.copyBytes (in, System.out, 4096, false);} finally {IOUtils.closeStream (in);}

Second, operate HDFS through FileSystem API

HDFS utility class

Import java.io.IOException;import org.apache.hadoop.conf.Configuration;import org.apache.hadoop.fs.FileSystem;public class HDFSUtils {/ * HDFS utility class * / public static FileSystem getFileSystem () {/ / declare FileSystem FileSystem hdfs=null; try {/ / get file configuration information Configuration conf = new Configuration () / / get file system hdfs=FileSystem.get (conf);} catch (IOException e) {e.printStackTrace ();} return hdfs;}}

Common operation implementation class

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;import org.apache.hadoop.mapred.gethistory_jsp;import org.junit.Test Public class HDFSFsTest {/ * * read file contents @ Test public void testRead () throws Exception through FileSystem API operation HDFS * / / get file system FileSystem hdfs = HDFSUtils.getFileSystem (); / / file name Path path = new Path ("/ opt/data/test/touch.data") / / Open the file input stream FSDataInputStream inStream = hdfs.open (path); / / read the file to the console to display IOUtils.copyBytes (inStream, System.out, 4096, false); / / close the stream IOUtils.closeStream (inStream);} / / View the directory @ Test public void testList () throws Exception {FileSystem hdfs = HDFSUtils.getFileSystem () / / File name Path path = new Path ("/ opt/data"); FileStatus [] fileStatus = hdfs.listStatus (path); for (FileStatus file: fileStatus) {Path p = file.getPath (); String info = file.isDir ()? "directory": "file"; System.out.println (info + ":" + p);}} / create directory @ Test public void testDirectory () throws Exception {FileSystem hdfs = HDFSUtils.getFileSystem (); / / directory to be created Path path = new Path ("/ opt/data/dir"); boolean isSuccessful = hdfs.mkdirs (path) / / equivalent to mkdir-p / opt/data/dir String info = isSuccessful under linux? "success": "failure"; System.out.println ("create directory [" + path + "]" + info);} / / upload files-- put copyFromLocal @ Test public void testPut () throws Exception {FileSystem hdfs = HDFSUtils.getFileSystem (); / / local files (directory + file name) Path srcPath = new Path ("c:/0125.log") / / hdfs file upload path Path dstPath = new Path ("/ opt/data/dir/"); hdfs.copyFromLocalFile (srcPath, dstPath);} / create hdfs file and write content @ Test public void testCreate () throws Exception {FileSystem hdfs = HDFSUtils.getFileSystem (); Path path = new Path ("/ opt/data/dir/touch.data") / / create a file and get the output stream FSDataOutputStream fSDataOutputStream = hdfs.create (path); / / write data fSDataOutputStream.write ("Hello" .getBytes ()) through the output stream; fSDataOutputStream.writeUTF ("hello hadoop!"); IOUtils.closeStream (fSDataOutputStream);} / / File rename @ Test public void testRename () throws Exception {FileSystem hdfs = HDFSUtils.getFileSystem () Path oldPath = newPath ("/ opt/data/dir/touch.data"); Path newPath = newPath ("/ opt/data/dir/rename.data"); boolean flag = hdfs.rename (oldPath, newPath); System.out.println (flag);} / / Delete file public void testDelete () throws Exception {FileSystem hdfs = HDFSUtils.getFileSystem () Path path = new Path ("/ opt/data/dir/touch.data"); boolean flag = hdfs.deleteOnExit (path); System.out.println (flag);} / / Delete directory public void testDeleteDir () throws Exception {FileSystem hdfs = HDFSUtils.getFileSystem (); Path path = new Path ("/ opt/data/dir"); boolean flag = hdfs.delete (path, true) / / if the directory second parameter must be true System.out.println (flag);} / / find the location of a file in the hdfs cluster public void testLocation () throws Exception {FileSystem hdfs = HDFSUtils.getFileSystem (); Path path = new Path ("/ opt/data/test.file"); FileStatus fileStatus = hdfs.getFileStatus (path) BlockLocation [] blockLocations = hdfs.getFileBlockLocations (fileStatus, 0, fileStatus.getLen ()); for (BlockLocation blockLocation: blockLocations) {String [] hosts = blockLocation.getHosts (); for (String host: hosts) {System.out.print (host + ");} System.out.println () }} / / get all node name information on hdfs cluster public void testCluster () throws Exception {FileSystem hdfs = HDFSUtils.getFileSystem (); DistributedFileSystem distributedFileSystem = (DistributedFileSystem) hdfs; DatanodeInfo [] datanodeInfos = distributedFileSystem.getDataNodeStats (); for (DatanodeInfo datanodeInfo: datanodeInfos) {String hostName = datanodeInfo.getHostName (); System.out.println (hostName);}

Upload and merge small files to hdfs

Implementation idea: loop through the local file input stream

Import org.apache.hadoop.conf.Configuration;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 / * in the process of uploading copied files to hdfs, merge the file names on the file * * / public class PutMerge {/ * * @ param localDir * the local directory of files to be uploaded * @ param hdfsFile * HDFS Include path * / public static void put (String localDir, String hdfsFile) throws Exception {/ / get configuration information Configuration conf = new Configuration () Path localPath = new Path (localDir); Path hdfsPath = new Path (hdfsFile); / / get the local file system FileSystem localFs = FileSystem.getLocal (conf); / / get HDFS FileSystem hdfs = FileSystem.get (conf); / / all files in the specified directory of the local file system FileStatus [] status = localFs.listStatus (localPath) / / Open the output stream of the file on hdfs FSDataOutputStream fSDataOutputStream = hdfs.create (hdfsPath); / / Loop through the local file for (FileStatus fileStatus: status) {/ / get the file Path path = fileStatus.getPath (); System.out.println ("File is:" + path.getName ()) / / Open the file input stream FSDataInputStream fSDataInputStream = localFs.open (path); / / read and write the stream byte [] buff = new byte [1024]; int len = 0; while ((len = fSDataInputStream.read (buff)) > 0) {fSDataOutputStream.write (buff, 0, len) } fSDataInputStream.close ();} fSDataOutputStream.close ();} public static void main (String [] args) {String localDir= "D:/logs"; String hdfsFile= "hdfs://hadoop-master.dragon.org:9000/opt/data/logs.data"; try {put (localDir,hdfsFile) } catch (Exception e) {e.printStackTrace ();}

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