import java.io.IOException;

     import java.net.URI;

     import java.net.URISyntaxException;  

     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.FileUtil;

     import org.apache.hadoop.fs.Path;

     import org.apache.hadoop.io.IOUtils;  

     public class HDFSTest {  

         //在指定位置新建一个文件，并写入字符

         public static void WriteToHDFS(String file, String words) throws IOException, URISyntaxException

         {

             Configuration conf = new Configuration();

             FileSystem fs = FileSystem.get(URI.create(file), conf);

             Path path = new Path(file);

             FSDataOutputStream out = fs.create(path);   //创建文件  

             //两个方法都用于文件写入，好像一般多使用后者

             out.writeBytes(words);

             out.write(words.getBytes("UTF-8"));  

             out.close();

             //如果是要从输入流中写入，或是从一个文件写到另一个文件（此时用输入流打开已有内容的文件）

             //可以使用如下IOUtils.copyBytes方法。

             //FSDataInputStream in = fs.open(new Path(args[0]));

             //IOUtils.copyBytes(in, out, 4096, true)        //4096为一次复制块大小，true表示复制完成后关闭流

         }  

         public static void ReadFromHDFS(String file) throws IOException

         {

             Configuration conf = new Configuration();

             FileSystem fs = FileSystem.get(URI.create(file), conf);

             Path path = new Path(file);

             FSDataInputStream in = fs.open(path);  

             IOUtils.copyBytes(in, System.out, 4096, true);

             //使用FSDataInoutStream的read方法会将文件内容读取到字节流中并返回

             /**

              * FileStatus stat = fs.getFileStatus(path);

           // create the buffer

            byte[] buffer = new byte[Integer.parseInt(String.valueOf(stat.getLen()))];

            is.readFully(0, buffer);

            is.close();

                  fs.close();

            return buffer;

              */

         }  

         public static void DeleteHDFSFile(String file) throws IOException

         {

             Configuration conf = new Configuration();

             FileSystem fs = FileSystem.get(URI.create(file), conf);

             Path path = new Path(file);

             //查看fs的delete API可以看到三个方法。deleteonExit实在退出JVM时删除，下面的方法是在指定为目录是递归删除

             fs.delete(path,true);

             fs.close();

         }  

         public static void UploadLocalFileHDFS(String src, String dst) throws IOException

         {

             Configuration conf = new Configuration();

             FileSystem fs = FileSystem.get(URI.create(dst), conf);

             Path pathDst = new Path(dst);

             Path pathSrc = new Path(src);  

             fs.copyFromLocalFile(pathSrc, pathDst);

             fs.close();

         }  

         public static void ListDirAll(String DirFile) throws IOException

         {

             Configuration conf = new Configuration();

             FileSystem fs = FileSystem.get(URI.create(DirFile), conf);

             Path path = new Path(DirFile);  

             FileStatus[] status = fs.listStatus(path);

             //方法1

             for(FileStatus f: status)

             {

                 System.out.println(f.getPath().toString());

             }

             //方法2

             Path[] listedPaths = FileUtil.stat2Paths(status);

             for (Path p : listedPaths){

               System.out.println(p.toString());

             }

         }  

         public static void main(String [] args) throws IOException, URISyntaxException

         {

             //下面做的是显示目录下所有文件

             ListDirAll("hdfs://ubuntu:9000/user/kqiao");  

             String fileWrite = "hdfs://ubuntu:9000/user/kqiao/test/FileWrite";

             String words = "This words is to write into file!\n";

             WriteToHDFS(fileWrite, words);

             //这里我们读取fileWrite的内容并显示在终端

             ReadFromHDFS(fileWrite);

             //这里删除上面的fileWrite文件

             DeleteHDFSFile(fileWrite);

             //假设本地有一个uploadFile，这里上传该文件到HDFS

     //      String LocalFile = "file:///home/kqiao/hadoop/MyHadoopCodes/uploadFile";

     //      UploadLocalFileHDFS(LocalFile, fileWrite    );

         }

     }