HDFS常用API（1）

一、HDFS集群API所需要jar包的maven配置信息

        <dependency>
            <groupId>org.apache.hadoop</groupId>
            <artifactId>hadoop-common</artifactId>
            <version>2.8.4</version>
        </dependency>
        <dependency>
            <groupId>org.apache.hadoop</groupId>
            <artifactId>hadoop-hdfs</artifactId>
            <version>2.8.4</version>
        </dependency>    

二、从HDFS下载数据文件/上传文件到HDFS文件系统

　　思路：1.获取配置信息

　　　　　2.设置配置信息(块大小、副本数)

　　　　　3.构造客户端

　　　　　4.下载数据文件/上传数据文件

　　　　　5.关闭资源

　　(1)下载文件

/**
 * @author: PrincessHug
 * @date: 2019/3/18, 16:10
 * @Blog: https://www.cnblogs.com/HelloBigTable/
 */
public class HdfsClientDemo02 {
    public static void main(String[] args) throws URISyntaxException, IOException, InterruptedException {
        //配置信息对象
        Configuration conf = new Configuration();
        //设置具体配置信息
        conf.set("dfs.replication","2");
        //构造客户端
        FileSystem fs = FileSystem.get(new URI("hdfs://192.168.126.128:9000/"), conf, "root");

        //下载数据到本地
        fs.copyToLocalFile(new Path("/words1.txt"),new Path("f://words1.txt"));
        //关闭资源
        fs.close();
        System.out.println("下载完成");
    }
}

　　（2）上传文件

/**
 * @author: PrincessHug
 * @date: 2019/3/18, 11:53
 * @Blog: https://www.cnblogs.com/HelloBigTable/
 */
public class HdfsClientDemo01 {
    public static void main(String[] args) throws URISyntaxException, IOException, InterruptedException {
        //配置信息
        Configuration conf = new Configuration();
        //配置块大小和副本数
        conf.set("dfs.blocksize","64m");
        conf.set("dfs.replication","2");
        //构造客户端
        FileSystem fs = FileSystem.get(new URI("hdfs://192.168.126.128:9000/"), conf, "root");
        //上传文件到hdfs客户端
        fs.copyFromLocalFile(new Path("/root/love.tsv"),new Path("/love1.tsv"));
        //关闭资源
        fs.close();
        System.out.println("上传成功！");
    }
}

三、对HDFS系统进行操作的API

/**
 * @author: PrincessHug
 * @date: 2019/3/18, 16:16
 * @Blog: https://www.cnblogs.com/HelloBigTable/
 */
public class HdfsClientDemo {

    private static FileSystem fs = null;

    static {
        Configuration conf = new Configuration();
        conf.set("dfs.blocksize","64m");
        conf.set("dfs.replication","3");
        try {
            fs = FileSystem.get(new URI("hdfs://192.168.126.128:9000/"),conf,"root");
        } catch (IOException e) {
            e.printStackTrace();
        } catch (InterruptedException e) {
            e.printStackTrace();
        } catch (URISyntaxException e) {
            e.printStackTrace();
        }
    }

    /**
     * 创建文件夹方法
     * @throws IOException
     */
    public void mkDir(String path) throws IOException {
        fs.mkdirs(new Path(path));
        fs.close();
    }

    /**
     * 重命名或移动文件
     * @param path1
     * @param path2
     * @throws IOException
     */
    public void hdfsRename(String path1,String path2) throws IOException {
        fs.rename(new Path(path1),new Path(path2));
        fs.close();
    }

    /**
     * 删除文件或文件夹
     * @param path 路径
     * @throws IOException
     */
    public void delete(String path) throws IOException {
        fs.delete(new Path(path),true);
        fs.close();
    }

    /**
     * 列出hdfs指定的目录信息
     * @param path
     * @throws IOException
     */
    public void list(String path) throws IOException {
        RemoteIterator<LocatedFileStatus> iterator = fs.listFiles(new Path(path), true);
        while (iterator.hasNext()){
            //拿数据
            LocatedFileStatus status = iterator.next();
            System.out.println("文件的路径为：" + status.getPath());
            System.out.println("文件的块大小为：" + status.getBlockSize());
            System.out.println("文件的块信息为：" + Arrays.toString(status.getBlockLocations()));
            System.out.println("文件的长度为：" + status.getLen());
            System.out.println("文件的副本数为：" + status.getReplication());
            System.out.println("=====================================================");
        }
        fs.close();
    }

    /**
     * 判断时文件还是文件夹
     * @param parh
     * @throws IOException
     */
    public void judgeFileOrDir(String parh) throws IOException {
        //展示状态信息
        FileStatus[] fileStatuses = fs.listStatus(new Path(parh));
        //遍历所有文件
        for (FileStatus fs:fileStatuses){
            if (fs.isFile()){
                System.out.println("文件-----f------" + fs.getPath().getName());
            }else {
                System.out.println("文件-----d------" + fs.getPath().getName());
            }
        }
    }
}

public class HdfsDriver {
    public static void main(String[] args) {
        HdfsClientDemo hcd = new HdfsClientDemo();
        try {
            //hcd.mkDir("/wyh");
            hcd.judgeFileOrDir("/");
            hcd.list("/");
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

四、

原文地址：https://www.cnblogs.com/HelloBigTable/p/10581676.html