Hadoop HDFS Java API

package com.uplooking.bigdata.hdfs;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.*;
import org.apache.hadoop.fs.permission.FsPermission;
import org.apache.hadoop.io.IOUtils;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.URI;
import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Date;

/**
 * 列出目录的内容：listStatus
 * 读取文件：open
 * 创建目录：mkdirs
 * 创建文件：create
 * 删除文件或目录：delete
 * 显示文件存储位置：getFileBlockLocations
 */
public class HDFSTest {
    private FileSystem fs;
    private DateFormat df = new SimpleDateFormat("yyyy-MM-dd HH:mm");

    /**
     * 初始化资源
     * @throws Exception
     */
    @Before
    public void setUp() throws Exception {
        URI uri = new URI("hdfs://uplooking01:9000");
        Configuration configuration = new Configuration();
        fs = FileSystem.get(uri, configuration);
    }

    /**
     * 列出目录的内容：listStatus
     * 模仿：
     * $ hdfs dfs -ls /
     * -rw-r--r--   1 uplooking supergroup         28 2018-02-28 12:29 /hello
     * drwxr-xr-x   - uplooking supergroup          0 2018-02-28 12:31 /output
     * drwx------   - uplooking supergroup          0 2018-02-28 12:31 /tmp
     *
     * @throws IOException
     */
    @Test
    public void testList() throws IOException {
        FileStatus[] fileStatuses = fs.listStatus(new Path("/"));
        for (FileStatus fileStatus : fileStatuses) {
            // 先定义好需要判断才能确定的项
            String prefix = "d";
            String repliaction = "-";

            // 获取文件类型
            if (fileStatus.isFile()) {
                prefix = "-";
            }

            // 获取权限列表
            FsPermission permission = fileStatus.getPermission();
            String uacl = permission.getUserAction().SYMBOL;
            String gacl = permission.getGroupAction().SYMBOL;
            String oacl = permission.getOtherAction().SYMBOL;
            String acl = uacl + gacl + oacl;

            // 获取复制因子数
            if (fileStatus.isFile()) {
                repliaction = fileStatus.getReplication() + "";
            }

            // 获取文件属主
            String owner = fileStatus.getOwner();
            // 获取文件属组
            String group = fileStatus.getGroup();

            // 获取文件大小
            long len = fileStatus.getLen();
            // 获取文件修改时间
            String mTime = df.format(new Date(fileStatus.getModificationTime()));
            // 获取文件路径
            Path path = fileStatus.getPath();

            // 格式化输出
            System.out.println(prefix + acl + "\t" + repliaction + "\t" + owner + "  " + group + "\t" + mTime + "\t" + path);
        }
    }

    /**
     * 读取文件：open
     *
     * @throws IOException
     */
    @Test
    public void testOpen() throws IOException {
        FSDataInputStream fis = fs.open(new Path("hdfs://uplooking01:9000/hello"));
        // 方式1：
       /* byte[] bytes = new byte[1024];
        int len = 0;
        while ((len = fis.read(bytes)) != -1) {
            System.out.println(new String(bytes, 0, len));
        }
        fis.close();*/

        // 方式2：
        /*BufferedReader br = new BufferedReader(new InputStreamReader(fis));
        String line = null;
        while ((line = br.readLine()) != null) {
            System.out.println(line);
        }
        fis.close();*/

        // 方式3：
        IOUtils.copyBytes(fis, System.out, 1024, false);
    }

    /**
     * 创建目录：mkdirs
     *
     * @throws IOException
     */
    @Test
    public void testMkdir() throws IOException {
        boolean ret = fs.mkdirs(new Path("/input/hdfs"));
        System.out.println(ret ? "创建目录成功" : "创建目录失败");
    }

    /**
     * 创建文件：create
     *
     * @throws IOException
     */
    @Test
    public void testCreate() throws IOException {
        // 第二个参数为是否覆盖，Files are overwritten by default
        FSDataOutputStream fos = fs.create(new Path("/input/hdfs/word.txt"), false);
        fos.write("hello\n".getBytes());
        fos.write("xpleaf\n".getBytes());
        fos.close();
    }

    /**
     * 删除文件或目录：delete
     *
     * @throws IOException
     */
    @Test
    public void testDelete() throws IOException {
        // 第二个参数为是否递归删除（当删除目录时）
        boolean ret = fs.delete(new Path("/input/hdfs/word.txt"), false);
        System.out.println(ret ? "删除成功" : "删除失败");
    }

    /**
     * 显示文件存储位置：getFileBlockLocations
     *
     * @throws IOException
     */
    @Test
    public void testLocations() throws IOException {
        Path path = new Path("/hadoop-2.6.4.tar.gz");
        FileStatus fileStatus = fs.getFileStatus(path);
        // 参数分别为：文件路径   偏移起始位置  文件长度
        BlockLocation[] locations = fs.getFileBlockLocations(path, 0, fileStatus.getLen());
        System.out.println(locations);
        for (BlockLocation location : locations) {
            System.out.println(location);
        }
        /**
         * 0,134217728,uplooking01          （偏移量从0开始，大小为128MB的块存储在节点uplooking01上）
           134217728,61798247,uplooking01   （偏移量从128M开始，大小为59M的块（就是剩余大小）存储在节点uplooking01上）
           可以看到，两个块都只存在uplooking01上的，这是因为这里的hadoop环境是伪分布式的
         */
    }

    /**
     * 释放资源
     * @throws IOException
     */
    @After
    public void cleanUp() throws IOException {
        fs.close();
    }
}