腾科教育以为理论+实操为主的教学，带你进入大数据开发基础。每一步都带着你，让你一步一步实现自已的大数据开发梦想。

构建maven工程

导入maven类包

 <dependencies>

    <dependency>

      <groupId>junit</groupId>

      <artifactId>junit</artifactId>

      <version>4.11</version>

      <scope>test</scope>

    </dependency>

    <dependency>

      <groupId>org.apache.hadoop</groupId>

      <artifactId>hadoop-client</artifactId>

      <version>2.8.1</version>

    </dependency>

  </dependencies>

编写Junit单元测试类

package net.togogo.hdfsproject;

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;

public class HdfsClientTest {

    FileSystem fs = null;

    @Before

    public void init() throws Exception {

        // 构造一个配置参数对象，设置一个参数：我们要访问的hdfs的URI

        // 从而FileSystem.get()方法就知道应该是去构造一个访问hdfs文件系统的客户端，以及hdfs的访问地址

        // new Configuration();的时候，它就会去加载jar包中的hdfs-default.xml

        // 然后再加载classpath下的hdfs-site.xml

        Configuration conf = new Configuration();

        conf.set("fs.defaultFS", "hdfs://192.168.75.129:9000");

        /**

         * 参数优先级： 1、客户端代码中设置的值 2、classpath下的用户自定义配置文件 3、然后是服务器的默认配置

         */

        conf.set("dfs.replication", "3");

        // 获取一个hdfs的访问客户端，根据参数，这个实例应该是DistributedFileSystem的实例

        // fs = FileSystem.get(conf);

        // 如果这样去获取，那conf里面就可以不要配"fs.defaultFS"参数，而且，这个客户端的身份标识已经是hadoop用户

        fs = FileSystem.get(new URI("hdfs://192.168.75.129:9000"), conf, "hadoop");

    }

    @Test

    public void testAddFileToHdfs(){

        // 要上传的文件所在的本地路径

        Path src = new Path("D:\\stone\\HCNA-AI\\images\\idcard.jpg");

        // 要上传到hdfs的目标路径

        Path dst = new Path("/togogo/idcard.jpg");

        try {

            fs.copyFromLocalFile(src,dst);

            System.out.println("文件上传成功...");

        } catch (IOException e) {

            e.printStackTrace();

        }

    }

    @Test

    public void testDelFileFromHdfs(){

        // 要上传到hdfs的目标路径

        Path dst = new Path("/togogo/work");

        try {

           fs.delete(dst,true);

            System.out.println("文件删除成功...");

        } catch (IOException e) {

            e.printStackTrace();

        }

    }

    /**

     * 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 {

        // 思考：为什么返回迭代器，而不是List之类的容器

        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("--------------为angelababy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 {

        FileStatus[] listStatus = fs.listStatus(new Path("/"));

        String flag = "d--             ";

        for (FileStatus fstatus : listStatus) {

            if (fstatus.isFile())  flag = "f--         ";

            System.out.println(flag + fstatus.getPath().getName());

        }

    }

}