HDFS常用API（2）

一、读取HDFS文件数据、将本地文件写入HDFS中文件、使用IOUtils读写数据

**
 * @author: PrincessHug
 * @date: 2019/3/18, 17:24
 * @Blog: https://www.cnblogs.com/HelloBigTable/
 */
public class HdfsClientDemo03 {
    FileSystem fs = null;
    Configuration conf = null;

    @Before
    public void init() throws URISyntaxException, IOException, InterruptedException {
        conf = new Configuration();
        fs = FileSystem.get(new URI("hdfs://192.168.126.128:9000/"),conf,"root");
    }

    /**
     * 使用缓冲流读数据
     * @throws IOException
     */
    @Test
    public void ReadData01() throws IOException {
        FSDataInputStream in = fs.open(new Path("/words1.txt"));
        BufferedReader br = new BufferedReader(new InputStreamReader(in, "UTF-8"));
        String line = null;
        //读数据
        while ((line = br.readLine()) != null){
            System.out.println(line);
        }
        //关闭资源
        br.close();
        in.close();
        fs.close();
    }

    /**
     * 使用字节数据来接收数据
     * @throws IOException
     */
    @Test
    public void ReadData02() throws IOException {
        FSDataInputStream in = fs.open(new Path("/words1.txt"));
        byte[] bytes = new byte[1024];
        in.read(bytes);
        System.out.println(new String(bytes));
        in.close();
        fs.close();
    }

    /**
     * 读取自定义偏移量的数据
     * @throws IOException
     */
    @Test
    public void randomRead() throws IOException {
        FSDataInputStream in = fs.open(new Path("/words1.txt"));
        in.seek(10);
        byte[] bytes = new byte[1024];
        in.read(bytes);
        System.out.println(new String(bytes));
        in.close();
    }

    /**
     * 从本地文件读取数据写入hdfs文件中
     * @throws IOException
     */
    @Test
    public void writeData() throws IOException {
        FSDataOutputStream out = fs.create(new Path("/window1.txt"), false);
        FileInputStream in = new FileInputStream("G:\潭州课堂笔记视频作业\java\集合.txt");
        byte[] bytes = new byte[1024];
        int read = 0;
        while ((read = in.read(bytes)) != -1){
            out.write(bytes,0,read);
        }
        in.close();
        out.close();
        fs.close();
    }

    /**
     * 向hdfs文件中写自定义的数据
     */
    @Test
    public void writeData01() throws IOException {
        FSDataOutputStream out = fs.create(new Path("/Wyh"));
        out.write("I love dilireba".getBytes());
        out.close();
        fs.close();
    }

    /**
     * 使用IOUtils的传输流方法上传文件
     * @throws IOException
     */
    @Test
    public void putFileToHdfs() throws IOException {
        //从本地文件获取数据流
        FileInputStream fis = new FileInputStream(new File("G:\潭州课堂笔记视频作业\java\多线程.txt"));
        //定义输出流对象
        FSDataOutputStream fos = fs.create(new Path("/threads.txt"));
        //流的传输
        IOUtils.copyBytes(fis,fos,conf);
        //关闭流
        IOUtils.closeStream(fis);
        IOUtils.closeStream(fos);
        fs.close();
    }

    @Test
    public void getFileFromHdfs() throws IOException {
        //从hdfs文件获取输入流
        FSDataInputStream fis = fs.open(new Path("/threads.txt"));
        //定义输出流对象
        FileOutputStream fos = new FileOutputStream(new File("G:\潭州课堂笔记视频作业\java\threads.txt"));
        //流的传输
        IOUtils.copyBytes(fis,fos,conf);
        //关闭流
        IOUtils.closeStream(fis);
        IOUtils.closeStream(fos);
        fs.close();
    }
}