hadoop3自学入门笔记(3)-java 操作hdfs

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>

2.pom.xml

<?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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