Hadoop 之 HDFS 配置与使用（二）

一.HDFS配置

## 基于上一篇文章进入 HADOOP_HOME 目录
cd $HADOOP_HOME/etc/hadoop
## 修改文件权限
chown -R root:root /usr/local/hadoop/hadoop-3.3.6/*
## 修改配置给文件：core-site.xml 和 hdfs-site.xml
vim core-site.xml
vim hdfs-site.xml

给 core-site.xml 添加如下信息

    hadoop.http.staticuser.user
    root


    fs.defaultFS
    hdfs://<你的IP>:9000

给 hdfs-site.xml 添加如下信息

	dfs.replication
	1

## 格式化文件结构
hdfs namenode -format
## 修改环境配置信息添加如下内容
vim hadoop-env.sh

export JAVA_HOME=/usr/local/java/jdk-11.0.19/
export HDFS_NAMENODE_USER=root
export HDFS_DATANODE_USER=root
export HDFS_SECONDARYNAMENODE_USER=root
export YARN_RESOURCEMANAGER_USER=root
export YARN_NODEMANAGER_USER=root

## 关闭并禁用防火墙
systemctl stop firewalld
systemctl disable firewalld
## 启动 HDFS
start-dfs.sh
## 查看进程
jps

## 停止 HDFS
stop-dfs.sh

查看 HDFS 自带面板：http://192.168.1.6:9870/

二.HDFS Shell

1.默认配置说明

hdfs-site.xml 文件中设置 dfs.name.dir 和 dfs.data.dir 
dfs.name.dir 的默认值为 ${hadoop.tmp.dir}/dfs/name
dfs.data.dir 的默认值为 ${hadoop.tmp.dir}/dfs/data
hadoop.tmp.dir 的值如果未使用 -D 选项或配置文件设置，则默认值为 /tmp/hadoop-${user.name}

默认值可参考如下文件
core-default.xml、hdfs-default.xml 和 mapred-default.xml

2.shell 命令

# 显示根目录 / 下的文件和子目录，绝对路径
hadoop fs -ls /
# 新建文件夹，绝对路径
hadoop fs -mkdir /testData
## 创建文件
echo 123 >> /home/test.txt
# 上传文件
hadoop fs -put /home/test.txt /testData/
# 下载文件
hadoop fs -get /testData/test.txt
# 输出文件内容
hadoop fs -cat /testData/test.txt

查看目录：hadoop fs -ls /

通过UI查看文件

三.Java 读写 HDFS

在本地idea上运行Hadoop相关服务，控制台打印出此错误“HADOOP_HOME and hadoop.home.dir are unset”，需要在本地Windows系

统配置 Hadoop 环境变量（重启IDEA）

GitHub 下载包路径

解压取出对应版本放到某个目录，如：D:\hadoop-3.3.5\bin

添加到环境变量 HADOOP_HOME

修改 PATH

1.Java 工程配置

Xml 配置

<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0modelVersion>

    <groupId>org.examplegroupId>
    <artifactId>HadoopDemoartifactId>
    <version>1.0-SNAPSHOTversion>

    <properties>
        <maven.compiler.source>19maven.compiler.source>
        <maven.compiler.target>19maven.compiler.target>
        <project.build.sourceEncoding>UTF-8project.build.sourceEncoding>
        <spring.version>3.1.1spring.version>
        <hadoop.version>3.3.6hadoop.version>
    properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.bootgroupId>
            <artifactId>spring-boot-starter-webartifactId>
            <version>${spring.version}version>
        dependency>
        <dependency>
            <groupId>org.springframework.bootgroupId>
            <artifactId>spring-boot-starter-log4j2artifactId>
            <version>${spring.version}version>
        dependency>
        <dependency>
            <groupId>org.springframework.bootgroupId>
            <artifactId>spring-boot-starter-aopartifactId>
            <version>${spring.version}version>
        dependency>
        <dependency>
            <groupId>org.projectlombokgroupId>
            <artifactId>lombokartifactId>
            <version>1.18.26version>
        dependency>
        <dependency>
            <groupId>com.alibabagroupId>
            <artifactId>fastjsonartifactId>
            <version>2.0.32version>
        dependency>
        
        <dependency>
            <groupId>org.apache.hadoopgroupId>
            <artifactId>hadoop-clientartifactId>
            <version>${hadoop.version}version>
        dependency>

    dependencies>

project>

启动类

package org.example;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

/**
 * @author Administrator
 */
@SpringBootApplication
public class HadoopApp {
    public static void main(String[] args) {
        SpringApplication.run(HadoopApp.class,args);
    }
}

读写类

package org.example.controller;

import jakarta.annotation.PostConstruct;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FSDataInputStream;
import org.apache.hadoop.fs.FSDataOutputStream;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import java.io.IOException;

/**
 * @author Administrator
 * @Description
 * @create 2023-07-13 23:19
 */
@RestController
@RequestMapping("/test")
public class TestController {

    @PostConstruct
    public void init(){
        System.setProperty("HADOOP_USER_NAME","root");
    }

    @GetMapping("/get")
    public String get(){
        String result = "";
        try {
            // 配置连接地址
            Configuration conf = new Configuration();
            conf.set("fs.defaultFS", "hdfs://192.168.1.6:9000");
            FileSystem fs = FileSystem.get(conf);
            // 打开文件并读取输出
            Path path = new Path("/testData/test.txt");
            FSDataInputStream ins = fs.open(path);
            StringBuilder builder = new StringBuilder();
            int ch = ins.read();
            while (ch != -1) {
                builder.append((char)ch);
                ch = ins.read();
            }
            result = builder.toString();
        } catch (IOException ioe) {
            ioe.printStackTrace();
        }
        return result;
    }


    @GetMapping("/set")
    public void set() {
        FileSystem fs = null;
        FSDataOutputStream ws = null;
        try {
            // 配置连接地址
            Configuration conf = new Configuration();
            conf.set("fs.defaultFS", "hdfs://192.168.1.6:9000");
            fs = FileSystem.get(conf);
            // 打开文件并读取输出
            Path path = new Path("/testData/test.txt");
            ws = fs.append(path);
            ws.writeBytes("Hello World!");
        } catch (IOException ioe) {
            ioe.printStackTrace();
        } finally {
            if (null != fs){
                try {
                    fs.close();
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            }
            if (null != ws){
                try {
                    ws.close();
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            }
        }
    }
}

2.测试

读数据

写数据

读数据

Windows 下 JDK 版本为 19