Java Operations for Hadoop HDFs

Access the files on HDFs and write them out to the output station

/*** Access the files on HDFs and write them out to the output station *@paramargs*/     Public Static voidMain (string[] args) {Try {            //converts the URL of the HDFS format to a system-recognizedUrl.seturlstreamhandlerfactory (Newfsurlstreamhandlerfactory ()); URL URL=NewURL ("Hdfs://hadoop1:9000/hello"); InputStream in=Url.openstream (); /*** Writes the read data to a file, does not need to control the buffer itself, and does not need to read the input stream yourself *@paramIn input stream *@paramout Stream *@parambuffersize Change to area size *@paramClose whether to close the stream, or false to close the * Ioutils.closestream (in) in the finally; */ioutils.copybytes (in, System.out,1024,true); } Catch(Exception e) {e.printstacktrace (); }    }

Get filesystem

/**      * Get filesystem     * Read     files using hadoop filesystem * * public     static throws IOException,            urisyntaxexception {        = filesystem.get (newnew  Configuration ());         return fileSystem;    }

Create a folder

/*** Create folder *@throwsurisyntaxexception*/     Public Static voidmkdir ()throwsIOException, urisyntaxexception {FileSystem FileSystem=Getfilesystem (); //Create a folder on HDFs and return the label of whether the creation was successful        BooleanSuccessful = Filesystem.mkdirs (NewPath ("/dir1")); if(successful) {SYSTEM.OUT.PRINTLN ("Create folder Succeeded"); }    }

Upload

/*** Upload *@throwsurisyntaxexception*/     Public Static voidPutData ()throwsIOException, FileNotFoundException, urisyntaxexception {FileSystem FileSystem=Getfilesystem (); //Create an upload path that returns the output streamFsdataoutputstream OS = filesystem.create (NewPath ("/dir1/readme")); FileInputStream in=NewFileInputStream ("D:\\Program files\\others\\2345soft\\haozip\\2345 Good Press disclaimer"); Ioutils.copybytes (in, OS,1024,true); }

Download

/*** Download *@throwsurisyntaxexception*/     Public Static voidDownload ()throwsIOException, urisyntaxexception {FileSystem FileSystem=Getfilesystem (); Fsdatainputstream in= Filesystem.open (NewPath ("Hdfs://hadoop1:9000/hello")); //closing the stream needs to be closed manually, System.out is also an output stream, and if true, it will not output theIoutils.copybytes (in, System.out, 1024,false);    In.close (); }

Delete a file or folder

/**Delete a file or folder * True: Indicates whether to delete recursively, if it is a file, here is True,false is indifferent, * folder must be true, otherwise error *@throwsurisyntaxexception*/     Public Static voidDelete ()throwsIOException, urisyntaxexception {FileSystem FileSystem=Getfilesystem (); BooleanisDeleted = Filesystem.delete (NewPath ("/dir1"),true); if(isDeleted) {System.out.println ("Delete Succeeded"); }    }

Traverse Directory

    /**Traverse Directory * Call FileSystem's Liststatus method * View file status using Filestatus *@throwsurisyntaxexception*/     Public Static voidList ()throwsIOException, urisyntaxexception {FileSystem FileSystem=Getfilesystem (); Filestatus[] Liststatus= Filesystem.liststatus (NewPath ("/"));  for(Filestatus filestatus:liststatus) {String Isdir= Filestatus.isdir ()? " Directory ":" File "; String name=Filestatus.getpath (). GetName (). toString (); System.out.println (Isdir+ "-+" +name); }    }

Java Operations for Hadoop HDFs