HDFS Java api操作

新建一个maven工程

在pom.xml中添加相关依赖

<?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.lzc.hadoop</groupId>
  <artifactId>hadoop-api</artifactId>
  <version>1.0-SNAPSHOT</version>

  <name>hadoop-api</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>
    <hadoop.version>2.6.0-cdh5.7.0</hadoop.version>
  </properties>

    <repositories>
        <repository>
            <id>cloudera</id>
            <url>https://repository.cloudera.com/artifactory/cloudera-repos</url>
        </repository>
    </repositories>

  <dependencies>

    <dependency>
      <groupId>org.apache.hadoop</groupId>
      <artifactId>hadoop-client</artifactId>
      <version>${hadoop.version}</version>
    </dependency>

    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.10</version>
      <scope>test</scope>
    </dependency>
  </dependencies>

</project>

基本操作

package com.lzc.hadoop.hdfs;

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

import java.io.*;
import java.net.URI;

/**
 * hadoop hdfs java api操作
 */
public class HDFSApp {

    public static final String HDFS_PATH = "hdfs://192.168.126.129:8020";

    FileSystem fileSystem = null;
    Configuration configuration = null;

    @Before
    public void setUp() throws Exception {
        System.out.println("HDFSApp.setUp");
        configuration = new Configuration();
        configuration.set("dfs.replication", "1"); // 设置hdfs副本，如果不设置，默认采用的是hadoop自己的副本系数
        fileSystem = FileSystem.get(new URI(HDFS_PATH), configuration, "root");
    }

    @After
    public void tearDown() {
        configuration = null;
        fileSystem = null;
        System.out.println("HDFSApp.tearDown");
    }

    /**
     * 创建hdfs目录
     */
    @Test
    public void mkdir() throws Exception {
        fileSystem.mkdirs(new Path("/hdfsapi/"));
    }

    /**
     *创建文件
     */
    @Test
    public void create() throws Exception {
        FSDataOutputStream outputStream =  fileSystem.create(new Path("/hdfsapi/lzc.txt"));
        outputStream.write("lzc hello".getBytes());
        outputStream.flush();
        outputStream.close();
    }

    /**
     *查看hdfs文件内容
     */
    @Test
    public void cat() throws Exception {
        FSDataInputStream inputStream = fileSystem.open(new Path("/hdfsapi/test.txt"));
        IOUtils.copyBytes(inputStream, System.out, 1024);
        inputStream.close();
    }

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

    /**
     *上传文件到hdfs
     * @throws Exception
     */
    @Test
    public void copyFromLocal() throws Exception {
        Path localPath = new Path("F:\\test.txt");
        Path hdfsPath = new Path("/hdfsapi/");
        fileSystem.copyFromLocalFile(localPath,hdfsPath);
    }

    /**
     *上传文件到hdfs
     * @throws Exception
     */
    @Test
    public void copyFromLocalWithProgress() throws Exception {
        InputStream in = new BufferedInputStream(new FileInputStream(new File("F:\\jdk-8u162-windows-x64.exe")));
        FSDataOutputStream output =  fileSystem.create(new Path("/hdfsapi/jdk.exe"), new Progressable() {
            @Override
            public void progress() {
                System.out.print("=>");
            }
        });
        IOUtils.copyBytes(in, output, 4096);
    }

    /**
     *下载hdfs文件
     * @throws Exception
     */
    @Test
    public void copyToLocalFile() throws Exception {
        Path localPath = new Path("F:\\hh.txt");
        Path hdfsPath = new Path("/hdfsapi/test.txt");
        fileSystem.copyToLocalFile(false, hdfsPath, localPath, true);
    }

    /**
     *查看hdfs某个目录下的所有文件
     * @throws Exception
     */
    @Test
    public void listFiles() throws Exception {
        FileStatus[] fileStatus = fileSystem.listStatus(new Path("/"));
        for (FileStatus f : fileStatus) {
            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);
        }
    }

    /**
     *查看hdfs某个目录下的所有文件
     * @throws Exception
     */
    @Test
    public void delete() throws Exception {
        fileSystem.delete(new Path("/hdfsapi/jdk.exe"), true);
    }


}