大家好，我是考100分的小小码 ，祝大家学习进步，加薪顺利呀。今天说一说hadoop3自学入门笔记(3)-java 操作hdfs[亲测有效],希望您对编程的造诣更进一步.
1.core-site.xml
<configuration>
<property>
<name>fs.defaultFS</name>
<value>hdfs://192.168.3.61:9820</value>
</property>
<property>
<name>hadoop.tmp.dir</name>
<value>/opt/hadoopdata</value>
</property>
</configuration>代码100分
2.pom.xml
代码100分<?xml version="1.0" encoding="UTF-8"?>
<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>4.0.0</modelVersion>
<groupId>com.qmkj</groupId>
<artifactId>hdfsclienttest</artifactId>
<version>0.1</version>
<name>hdfsclienttest</name>
<!-- FIXME change it to the project's website -->
<url>http://www.example.com</url>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<maven.compiler.source>1.7</maven.compiler.source>
<maven.compiler.target>1.7</maven.compiler.target>
</properties>
<dependencies>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.11</version>
<scope>test</scope>
</dependency>
<!-- https://mvnrepository.com/artifact/org.apache.hadoop/hadoop-hdfs-client -->
<dependency>
<groupId>org.apache.hadoop</groupId>
<artifactId>hadoop-hdfs-client</artifactId>
<version>3.2.1</version>
<scope>provided</scope>
</dependency>
<!-- https://mvnrepository.com/artifact/org.apache.hadoop/hadoop-common -->
<dependency>
<groupId>org.apache.hadoop</groupId>
<artifactId>hadoop-common</artifactId>
<version>3.2.1</version>
</dependency>
<!-- https://mvnrepository.com/artifact/org.apache.hadoop/hadoop-hdfs -->
<dependency>
<groupId>org.apache.hadoop</groupId>
<artifactId>hadoop-hdfs</artifactId>
<version>3.2.1</version>
</dependency>
</dependencies>
<build>
<pluginManagement><!-- lock down plugins versions to avoid using Maven defaults (may be moved to parent pom) -->
<plugins>
<!-- clean lifecycle, see https://maven.apache.org/ref/current/maven-core/lifecycles.html#clean_Lifecycle -->
<plugin>
<artifactId>maven-clean-plugin</artifactId>
<version>3.1.0</version>
</plugin>
<!-- default lifecycle, jar packaging: see https://maven.apache.org/ref/current/maven-core/default-bindings.html#Plugin_bindings_for_jar_packaging -->
<plugin>
<artifactId>maven-resources-plugin</artifactId>
<version>3.0.2</version>
</plugin>
<plugin>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.8.0</version>
</plugin>
<plugin>
<artifactId>maven-surefire-plugin</artifactId>
<version>2.22.1</version>
</plugin>
<plugin>
<artifactId>maven-jar-plugin</artifactId>
<version>3.0.2</version>
</plugin>
<plugin>
<artifactId>maven-install-plugin</artifactId>
<version>2.5.2</version>
</plugin>
<plugin>
<artifactId>maven-deploy-plugin</artifactId>
<version>2.8.2</version>
</plugin>
<!-- site lifecycle, see https://maven.apache.org/ref/current/maven-core/lifecycles.html#site_Lifecycle -->
<plugin>
<artifactId>maven-site-plugin</artifactId>
<version>3.7.1</version>
</plugin>
<plugin>
<artifactId>maven-project-info-reports-plugin</artifactId>
<version>3.0.0</version>
</plugin>
</plugins>
</pluginManagement>
</build>
</project>
3.测试代码
package com.qmkj;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.*;
import org.junit.Before;
import org.junit.Test;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.net.URI;
/**
* Unit test for simple App.
*/
public class AppTest {
FileSystem fs = null;
@Before
public void init() throws Exception {
Configuration conf = new Configuration();
//设立的设置url请注意，设置core-site.xml中配置fs.defaultFS的地址
fs = FileSystem.get(new URI("hdfs://192.168.3.61:9820"), conf, "root");
}
@Test
public void testAdd() throws Exception {
fs.copyFromLocalFile(new Path("D:\KK_Movies\kk 2020-02-20 20-45-55.mp4"), new Path("/zhanglei"));
fs.close();
}
/**
* 从hdfs中复制文件到本地文件系统
*
* @throws IOException
* @throws IllegalArgumentException
*/
@Test
public void testDownloadFileToLocal() throws IllegalArgumentException, IOException {
// fs.copyToLocalFile(new Path("/mysql-connector-java-5.1.28.jar"), new
// Path("d:/"));
fs.copyToLocalFile(false, new Path("test.txt"), new Path("e:/"), true);
fs.close();
}
/**
* 目录操作
*
* @throws IllegalArgumentException
* @throws IOException
*/
@Test
public void testMkdirAndDeleteAndRename() throws IllegalArgumentException, IOException {
// 创建目录
fs.mkdirs(new Path("/zhanglei/b1/c1"));
// 删除文件夹 ，如果是非空文件夹，参数2必须给值true ，删除所有子文件夹
fs.delete(new Path("/b1"), true);
// 重命名文件或文件夹
fs.rename(new Path("/zhanglei"), new Path("/qmkj"));
}
/**
* 查看目录信息，只显示文件
*
* @throws IOException
* @throws IllegalArgumentException
* @throws FileNotFoundException
*/
@Test
public void testListFiles() throws FileNotFoundException, IllegalArgumentException, IOException {
RemoteIterator<LocatedFileStatus> listFiles = fs.listFiles(new Path("/"), true);
while (listFiles.hasNext()) {
LocatedFileStatus fileStatus = listFiles.next();
System.out.println(fileStatus.getPath().getName());
System.out.println(fileStatus.getBlockSize());
System.out.println(fileStatus.getPermission());
System.out.println(fileStatus.getLen());
BlockLocation[] blockLocations = fileStatus.getBlockLocations();
for (BlockLocation bl : blockLocations) {
System.out.println("block-length:" + bl.getLength() + "--" + "block-offset:" + bl.getOffset());
String[] hosts = bl.getHosts();
for (String host : hosts) {
System.out.println(host);
}
}
System.out.println("--------------打印的分割线--------------");
}
}
/**
* 查看文件及文件夹信息
*
* @throws IOException
* @throws IllegalArgumentException
* @throws FileNotFoundException
*/
@Test
public void testListAll() throws FileNotFoundException, IllegalArgumentException, IOException {
//可以右击方法名，Run 测试一下。
FileStatus[] listStatus = fs.listStatus(new Path("/"));
String flag = "";
for (FileStatus fstatus : listStatus) {
if (fstatus.isFile()) {
flag = "f-- ";
} else {
flag = "d-- ";
}
System.out.println(flag + fstatus.getPath().getName());
System.out.println(fstatus.getPermission());
}
}
}
testDownloadFileToLocal 这里测试请注意，本地也要装hdfs才可以
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