java API 操作HDFS服务器

1.准备

　　开发环境：eclipse

　　依赖包：hadoop-2.7.7.tar.gz安装包　share/hadoop/下　common、hdfs中的jar包

2.连接HDFS服务器

    /**　　　* 连接HDFS服务器
     */
    @Test
    public void connectHDFS() {
        //做一个配置
        Configuration conf = new Configuration();
        //服务器地址 端口
        conf.set("fs.defaultFS", "hdfs://192.168.124.26:9000");
        try {
            //连接到服务器
            FileSystem fileSystem = FileSystem.get(conf);
            FileStatus fileStatus = fileSystem.getFileStatus(new Path("/upload/word.txt"));
            System.out.println(fileStatus.isFile());
            System.out.println(fileStatus.isDirectory());
            System.out.println(fileStatus.getPath());
            System.out.println(fileStatus.getLen());
            fileSystem.close();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

3.重命名（增删改操作需要使用root用户登陆）

    /**
     * 重命名
     */
    @Test
    public void mv() {
        Configuration conf = new Configuration();
        try {
            //修改文件名需要修改的权限，以root用户登陆HDFS
            FileSystem fileSystem = FileSystem.get(new URI("hdfs://192.168.124.26:9000"),conf,"root");
            boolean rename = fileSystem.rename(new Path("/upload/word.txt"), new Path("/upload/word2.txt"));
            System.out.println(rename?"修改成功":"修改失败");
            fileSystem.close();
        } catch (IOException | URISyntaxException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (InterruptedException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }        

4.创建文件夹

    /**
     * 创建文件夹
     */
    @Test
    public void mkdir() {
        Configuration conf = new Configuration();
        try {
            FileSystem fileSystem = FileSystem.get(new URI("hdfs://192.168.124.26:9000"),conf,"root");
            fileSystem.mkdirs(new Path("/user"));
            fileSystem.close();
        } catch (IOException | URISyntaxException | InterruptedException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

5.文件上传（使用byte[]）

    /**
     * 文件上传
     */
    @Test
    public void upload() {
        Configuration conf = new Configuration();
        try {
            FileSystem fileSystem = FileSystem.get(new URI("hdfs://192.168.124.26:9000"),conf,"root");
            FSDataOutputStream out = fileSystem.create(new Path("/upload/words.txt"));
            FileInputStream in = new FileInputStream(new File("E:\\words.txt"));
            byte[] b = new byte[1024];
            int len = 0;
            while((len=in.read(b))!=-1) {
                out.write(b,0,len);
            }
            in.close();
            out.close();
            fileSystem.close();
        } catch (IOException | URISyntaxException | InterruptedException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

6.文件上传（使用IOUtils工具包）

    /**
     * 文件上传 使用IOUtils简化步骤
     * jar包在commons-io中
     */
    @Test
    public void upload2() {
        Configuration conf = new Configuration();
        try {
            FileSystem fileSystem = FileSystem.get(new URI("hdfs://192.168.124.26:9000"), conf, "root");
            FSDataOutputStream out = fileSystem.create(new Path("/upload/words2.txt"));
            FileInputStream in = new FileInputStream(new File("E:/words.txt"));
            IOUtils.copyBytes(in, out, conf);
            fileSystem.close();
        } catch (IOException | InterruptedException | URISyntaxException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

7.文件下载

    /**
     * 文件下载
     */
    @Test
    public void download() {
        Configuration conf = new Configuration();
        try {
            FileSystem fileSystem = FileSystem.get(new URI("hdfs://192.168.124.26:9000"), conf);
            FSDataInputStream in = fileSystem.open(new Path("/upload/word2.txt"));
            FileOutputStream out = new FileOutputStream(new File("E:/word2.txt"));
            byte[] b = new byte[1024];
            int len = 0;
            while((len=in.read(b))!=-1) {
                out.write(b, 0, len);
            }
            in.close();
            out.close();
            fileSystem.close();
        } catch (IOException | URISyntaxException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

8.实现命令lsr，递归显示文件夹和文件

    /**
     * 实现命令lsr    递归显示文件夹和文件
     */
    @Test
    public void lrs() {
        Configuration conf = new Configuration();
        try {
            FileSystem fileSystem = FileSystem.get(new URI("hdfs://192.168.124.26:9000"),conf);
            isDir(fileSystem,new Path("/"));
            fileSystem.close();

        } catch (IOException | URISyntaxException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

    public void isDir(FileSystem fileSystem,Path path) {
        try {
            FileStatus[] listStatuses = fileSystem.listStatus(path);
            for(FileStatus listStatus:listStatuses) {
                Path path1 = listStatus.getPath();
                boolean directory = fileSystem.isDirectory(path1);
                if(directory) {
                    System.out.println("文件夹："+listStatus.getPath()+"\t"+listStatus.getLen()+"\t"+listStatus.getOwner()+"\t"+listStatus.getGroup());
                    isDir(fileSystem,path1);
                }else {
                    System.out.println("文件："+listStatus.getPath()+"\t"+listStatus.getLen()+"\t"+listStatus.getOwner()+"\t"+listStatus.getGroup());
                }
            }
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

原文地址：https://www.cnblogs.com/zhan98/p/12346731.html