hadoop之 HDFS讀寫 java interface

讀取文件

public static void readFile(String uri) {

        Configuration configuration = new Configuration();
        InputStream inputStream = null;
        try {
            // String uri = "hdfs://hadoop:9000/hadoop/temp/1901";
            FileSystem fileSystem = FileSystem.get(URI.create(uri), configuration);
            inputStream = fileSystem.open(new Path(uri));
            IOUtils.copyBytes(inputStream, System.out, 4096, false);
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            IOUtils.closeStream(inputStream);
        }
    }

seek 讀取

public static void readFileByFSDATAInputStream(String uri) {
        Configuration configuration = new Configuration();
        FSDataInputStream stream = null;
        try {
            FileSystem fileSystem = FileSystem.get(URI.create(uri), configuration);
            stream = fileSystem.open(new Path(uri));
            IOUtils.copyBytes(stream, System.out, 4096, false);

            stream.seek(0);
            IOUtils.copyBytes(stream, System.out, 4096, false);

        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            IOUtils.closeStream(stream);
        }
    }

寫文件

public static void writeData(String uri, String local) {


        try {
            InputStream inputStream = new BufferedInputStream(new FileInputStream(local));
            FileSystem fileSystem = FileSystem.get(configuration);


            // 建立一個新文件 必須保證uri不存在  若是向一個已經存在的文件添加內容，使用fileSystem.append(Path p)
            //fileSystem.exists(new Path("")); //判斷文件是否存在
            //fileSystem.mkdirs(new Path(""));  //建立文件夾
            FSDataOutputStream outputStream = fileSystem.create(new Path(uri), new Progressable() {
                // 報告寫入過程
                @Override
                public void progress() {
                    System.out.print(".");
                }
            });

            IOUtils.copyBytes(inputStream, outputStream, 4096, true);
        } catch (IOException e) {
            e.printStackTrace();
        }


    }

列出文件列表

public static void listFiles(String uri) {

        try {
            FileSystem fileSystem = FileSystem.get(configuration);
          //  FileStatus fileStatus = fileSystem.getFileStatus(new Path(uri));
            FileStatus[] statuses = fileSystem.listStatus(new Path(uri));
            Path[] listPaths = FileUtil.stat2Paths(statuses);
            for (Path path : listPaths){
                System.out.println(path);
            }
            // fileSystem.listStatus(Path[] files); //批量讀取

        } catch (IOException e) {
            e.printStackTrace();
        }

    }

刪除文件

public static void deleteFile(String uri){

        try {
            FileSystem fileSystem = FileSystem.get(configuration);
            fileSystem.delete(new Path(uri),true);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

源碼

/** Delete a file.
   *
   * @param f the path to delete.
   * @param recursive if path is a directory and set to 
   * true, the directory is deleted else throws an exception. In
   * case of a file the recursive can be set to either true or false. 
   * @return  true if delete is successful else false. 
   * @throws IOException
   */
  public abstract boolean delete(Path f, boolean recursive) throws IOException;

若是刪除文件夾須要 設置爲true，若是未flase會拋出異常。