Hadoop学习笔记之HDFS

Gettler•Main 2023-04-21 原文

Hadoop学习笔记之HDFS

HDFS （Hadoop Distributed File System）

HDFS （Hadoop Distributed File System）

分布式存储系统

支持海量数据的存储，成百上千的计算机组成存储集群，HDFS可以运行在低成本的硬件之上，具有的高容错、高可靠性、高可扩展性、高吞吐率等特征，非常适合大规模数据集上的应用。

优点

高容错性
适合批处理
适合大数据处理
流式文件访问
可构建在廉价机器上

缺点

不适合低延迟数据访问
不适合小文件存取
不适合并发写入、文件随机修改

HDFS操作

命令操作HDFS

# 显示目录 / 下的文件
hdfs dfs -ls /
# 新建文件夹，绝对路径
hdfs dfs -mkdir /test
# 上传文件
hdfs dfs -put test.txt /test/
# 下载文件
hdfs dfs -get /test/test.txt
# 输出文件内容
hdfs dfs -cat /test/test.txt

Web端操作HDFS

打开http://192.168.9.200:9870/，可以对HDFS进行操作

文件在这里管理

可视化操作还是简单一些

Java操作HDFS

添加依赖

<dependency>
    <groupId>org.apache.hadoop</groupId>
    <artifactId>hadoop-client</artifactId>
    <version>3.3.2</version>
</dependency>

建立连接

public void setUp() throws Exception {
    System.out.println("开始建立与HDFS的连接");
    configuration = new Configuration();
    fileSystem = FileSystem.get(new URI(HDFS_PATH), configuration, "hadoop");
}

文件操作

    Configuration configuration = null;
    FileSystem fileSystem = null;
    public static final String HDFS_PATH = "hdfs://192.168.9.200:9000";

    /**
     * 在 hdfs中新建文件夹
     *
     * @throws Exception
     */
    @Test
    public void mkdir() throws Exception {
        fileSystem.mkdirs(new Path("/JavaDemo/test"));
    }

    /**
     * 创建文件
     *
     * @throws Exception
     */

    @Test
    public void create() throws Exception {
        FSDataOutputStream outputStream = fileSystem.create(new Path("/JavaDemo/test/haha.txt"));
        outputStream.write("hello bigdata from javaDemo".getBytes());
        outputStream.flush();
        outputStream.close();
    }


    /**
     * 查看文件 hdfs -fs -cat file
     *
     * @throws Exception
     */
    @Test
    public void cat() throws Exception {
        FSDataInputStream in = fileSystem.open(new Path("/JavaDemo/test/haha.txt"));
        IOUtils.copyBytes(in, System.out, 1024);
        in.close();
    }

    /**
     * 重命名文件
     *
     * @throws Exception
     */
    @Test
    public void rename() throws Exception {
        Path oldPath = new Path("/JavaDemo/test/haha.txt");
        Path newPath = new Path("/JavaDemo/test/hehe.txt");
        fileSystem.rename(oldPath, newPath);
    }

    /**
     * 上传文件到HDFS
     *
     * @throws Exception
     */
    @Test
    public void copyFromLocalFile() throws Exception {
        Path loacalPath = new Path("hello.txt");
        Path hdfsPath = new Path("/");
        fileSystem.copyFromLocalFile(loacalPath, hdfsPath);
    }


    /**
     * 上传文件到HDFS带进度信息
     *
     * @throws Exception
     */

    @Test
    public void copyFromLocalFileWithProgress() throws Exception {
        InputStream in = new BufferedInputStream(Files.newInputStream(new File("hbase-2.2.7-bin.tar.gz").toPath()));
        FSDataOutputStream ouput = fileSystem.create(new Path("/JavaDemo/test/hbase-2.2.7-bin.tar.gz"), () -> {
            System.out.print(".");
        });
        IOUtils.copyBytes(in, ouput, 4096);
    }

    /**
     * 下载文件到HDFS
     *
     * @throws Exception
     */
    @Test
    public void copyToLocalFile() throws Exception {
        Path hdfsPath = new Path("/JavaDemo/test/haha.txt");
        Path loacalPath = new Path("./haha.txt");
        //  useRawLocalFileSystem
        fileSystem.copyToLocalFile(false, hdfsPath, loacalPath, true);
    }

    /**
     * 查看某个目录下所有文件
     *
     * @throws Exception
     */
    @Test
    public void listFiles() throws Exception {
        FileStatus[] fileStatuses = fileSystem.listStatus(new Path("/"));
        for (FileStatus f : fileStatuses) {
            String isDir = f.isDirectory() ? "文件夹" : "文件";
            short replication = f.getReplication();
            long len = f.getLen();
            String path = f.getPath().toString();

            System.out.println(isDir + "\t" + replication + "\t" + len + "\t" + path);

        }
    }

    /**
     * 删除文件
     *
     * @throws Exception
     */
    @Test
    public void delete() throws IOException {
        fileSystem.delete(new Path("/JavaDemo/haha.txt"), true);
    }

关闭连接

public void tearDown() {
    configuration = null;
    fileSystem = null;
    System.out.println("关闭与HDFS的连接");
}

完整测试文件

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

import java.io.*;
import java.net.URI;
import java.nio.file.Files;

/**
 * @author Gettler
 * Java 操作HDFS
 */
public class HdfsDemo {
    Configuration configuration = null;
    FileSystem fileSystem = null;
    public static final String HDFS_PATH = "hdfs://192.168.9.200:9000";

    /**
     * 在 hdfs中新建文件夹
     *
     * @throws Exception
     */
    @Test
    public void mkdir() throws Exception {
        fileSystem.mkdirs(new Path("/JavaDemo/test"));
    }

    /**
     * 创建文件
     *
     * @throws Exception
     */

    @Test
    public void create() throws Exception {
        FSDataOutputStream outputStream = fileSystem.create(new Path("/JavaDemo/test/haha.txt"));
        outputStream.write("hello bigdata from javaDemo".getBytes());
        outputStream.flush();
        outputStream.close();
    }


    /**
     * 查看文件 hdfs -fs -cat file
     *
     * @throws Exception
     */
    @Test
    public void cat() throws Exception {
        FSDataInputStream in = fileSystem.open(new Path("/JavaDemo/test/haha.txt"));
        IOUtils.copyBytes(in, System.out, 1024);
        in.close();
    }

    /**
     * 重命名文件
     *
     * @throws Exception
     */
    @Test
    public void rename() throws Exception {
        Path oldPath = new Path("/JavaDemo/test/haha.txt");
        Path newPath = new Path("/JavaDemo/test/hehe.txt");
        fileSystem.rename(oldPath, newPath);
    }

    /**
     * 上传文件到HDFS
     *
     * @throws Exception
     */
    @Test
    public void copyFromLocalFile() throws Exception {
        Path loacalPath = new Path("hello.txt");
        Path hdfsPath = new Path("/");
        fileSystem.copyFromLocalFile(loacalPath, hdfsPath);
    }


    /**
     * 上传文件到HDFS带进度信息
     *
     * @throws Exception
     */

    @Test
    public void copyFromLocalFileWithProgress() throws Exception {
        InputStream in = new BufferedInputStream(Files.newInputStream(new File("hbase-2.2.7-bin.tar.gz").toPath()));
        FSDataOutputStream ouput = fileSystem.create(new Path("/JavaDemo/test/hbase-2.2.7-bin.tar.gz"), () -> {
            System.out.print(".");
        });
        IOUtils.copyBytes(in, ouput, 4096);
    }

    /**
     * 下载文件到HDFS
     *
     * @throws Exception
     */
    @Test
    public void copyToLocalFile() throws Exception {
        Path hdfsPath = new Path("/JavaDemo/test/haha.txt");
        Path loacalPath = new Path("./haha.txt");
        //  useRawLocalFileSystem
        fileSystem.copyToLocalFile(false, hdfsPath, loacalPath, true);
    }

    /**
     * 查看某个目录下所有文件
     *
     * @throws Exception
     */
    @Test
    public void listFiles() throws Exception {
        FileStatus[] fileStatuses = fileSystem.listStatus(new Path("/"));
        for (FileStatus f : fileStatuses) {
            String isDir = f.isDirectory() ? "文件夹" : "文件";
            short replication = f.getReplication();
            long len = f.getLen();
            String path = f.getPath().toString();

            System.out.println(isDir + "\t" + replication + "\t" + len + "\t" + path);

        }
    }

    /**
     * 删除文件
     *
     * @throws Exception
     */
    @Test
    public void delete() throws IOException {
        fileSystem.delete(new Path("/JavaDemo/haha.txt"), true);
    }


    //测试之前执行的代码
    @Before
    public void setUp() throws Exception {
        System.out.println("开始建立与HDFS的连接");
        configuration = new Configuration();
        fileSystem = FileSystem.get(new URI(HDFS_PATH), configuration, "hadoop");
    }

    //测试之完执行的代码
    @After
    public void tearDown() {
        configuration = null;
        fileSystem = null;
        System.out.println("关闭与HDFS的连接");
    }
}

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笔记 Hadoop span class token hdfs 学习

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Hadoop学习笔记之HDFS