Hadoop之HDFS JavaAPI使用方法

上一篇我们讲到了用shell命令操作HDFS，现在用Java API操作HDFS。
开发工具：Idea+Maven
首先在Idea上创建一个Maven项目：hadooptrain.
POM文件如下所示：

<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>com.yoyocheknowgroupId>
    <artifactId>hadoop.trainartifactId>
    <version>1.0version>

    <properties>
        <project.build.sourceEncoding>UTF-8project.build.sourceEncoding>
        <hadoop.version>2.6.0-cdh5.7.0hadoop.version>
    properties>
    <repositories>
        <repository>
            <id>clouderaid>
            <url>https://repository.cloudera.com/artifactory/cloudera-reposurl>
        repository>
    repositories>
<dependencies>
    <dependency>
        <groupId>org.apache.hadoopgroupId>
        <artifactId>hadoop-clientartifactId>
        <version>${hadoop.version}version>
    dependency>
    <dependency>
        <groupId>junitgroupId>
        <artifactId>junitartifactId>
        <version>4.12version>
    dependency>
dependencies>
project>

项目结构如下所示：

创建test类。

package com.yoyocheknow.hadoop;


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.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.BufferedInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.InputStream;
import java.net.URI;

/**
 * 类说明
 * hadoop hdfs java api 操作
 * @author yoyocheknow
 * @date 2018/7/27 10:44
 */
public class AppTest {

    FileSystem  fileSystem=null;
    Configuration configuration=null;
    public static final String HDFS_PATH="hdfs://hadoopMaster:8020";
    @Before
    public void setup() throws Exception{
        System.out.println("HDFS.setup");
        configuration=new Configuration();
        fileSystem=FileSystem.get(new URI(HDFS_PATH),configuration,"root");
    }

    @After
    public void tearDown()throws Exception{
        configuration=null;
        fileSystem=null;
        System.out.println("HDFS.tearDown");
    }
    /*
     *创建目录
     */
    @Test
    public void mkdir()throws Exception{
        fileSystem.mkdirs(new Path("/hdfsapi/test"));
    }
    /*
     *创建文件
     */
    @Test
    public void create()throws Exception{
        FSDataOutputStream out=fileSystem.create(new Path("/hdfsapi/test/a.txt"));
        out.write("hello Hadoop".getBytes());
        out.flush();
        out.close();
    }
    /*
     *读取hdfs文件并打印在控制台
     */
    @Test
    public void cat() throws Exception{
        FSDataInputStream in=fileSystem.open(new Path("/hdfsapi/test/a.txt"));
        IOUtils.copyBytes(in, System.out,1024);
        in.close();
    }
    /*
     *重命名
     */
    @Test
    public void rename()throws Exception{
        Path oldPath= new Path("/hdfsapi/test/a.txt");
        Path newPath=new Path("/hdfsapi/test/b.txt");
        fileSystem.rename(oldPath,newPath);
    }
    /*
     *从本地 上传文件到hdfs
     */
    @Test
    public void copyFromLocalFiles()throws Exception{
        Path localParh= new Path("D:\\知乎-编辑推荐.txt");
        Path newPath=new Path("/hdfsapi/test");
        fileSystem.copyFromLocalFile(localParh,newPath);
    }
    /*
      *带进度条的上传
      */
    @Test
    public void copyFromLocalFileswithProgress()throws Exception{
        InputStream in =new BufferedInputStream(new FileInputStream(new File("D:\\[洋葱] 课时07：netty服务器的快速实现.mp4")));
       FSDataOutputStream outputStream=fileSystem.create(new Path("/hdfsapi/test/netty-vedio.mp4")
               , new Progressable() {
                   public void progress() {
                       System.out.print("*");
                   }
               });
      IOUtils.copyBytes(in,outputStream,4096);
    }
}