HDFS是一個分散式檔案系統，既然是檔案系統，就可以對其中的檔案進行操作，比如說新建資料夾、上傳檔案，重新命名檔案，下載檔案，刪除檔案、列舉所有檔案等操作。

HDFSClient.java

package com.looc.client;

import java.io.FileNotFoundException;
import java.io.IOException;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.LocatedFileStatus;
import
 
 org.apache.hadoop.fs.Path;
import org.apache.hadoop.fs.RemoteIterator;
import org.junit.Before;
import org.junit.Test;

public class HDFSClient {

    private FileSystem fileSystem = null;

    @Before
    public void getFileSystem() throws IOException {
        // 配置引數的封裝物件
        // 建構函式對xxx-site.xml檔案進行解析，真實專案中需要將xxx-site.xml檔案載入到工程中。
 

        Configuration configuration = new Configuration();
        configuration.set("fs.defaultFS", "hdfs://looc:9000");
        // 獲取檔案系統的客戶端例項物件，根據configuration中的相關引數決定。
        fileSystem = FileSystem.get(configuration);
    }

    /**
     * 建立資料夾
     * 
     * @throws IllegalArgumentException
     * @throws
 
 IOException
     */
    @Test
    public void testMkdir() throws IllegalArgumentException, IOException {
        fileSystem.mkdirs(new Path("/a/b/c"));
    }

    /**
     * 上傳檔案
     * 
     * @throws IllegalArgumentException
     * @throws IOException
     */
    @Test
    public void testUpload() throws IllegalArgumentException, IOException {
        fileSystem.copyFromLocalFile(new Path("E:\\MapReduce\\WordCount.txt"), new Path("/a/b/c"));
    }

    /**
     * 重新命名檔案
     * 
     * @throws IllegalArgumentException
     * @throws IOException
     */
    @Test
    public void testRename() throws IllegalArgumentException, IOException {
        fileSystem.rename(new Path("/a/b/c/WordCount.txt"), new Path("/a/b/c/WordCount.txt.rename"));
    }

    /**
     * 下載檔案
     * 
     * @throws IllegalArgumentException
     * @throws IOException
     */
    @Test
    public void testDownload() throws IllegalArgumentException, IOException {
        fileSystem.copyToLocalFile(new Path("/a/b/c/WordCount.txt.rename"), new Path("E:\\MapReduce"));
    }

    /**
     * 刪除檔案
     * 
     * @throws IllegalArgumentException
     * @throws IOException
     */
    @Test
    public void testRmfile() throws IllegalArgumentException, IOException {
        boolean result = fileSystem.delete(new Path("/a/b/c/WordCount.txt.rename"), true);
        System.out.println(result ? "DELETE IS SUCCESSFULLY!" : "DELETE IS FAILD!");
    }

    /**
     * 列舉所有檔案
     * 
     * @throws FileNotFoundException
     * @throws IllegalArgumentException
     * @throws IOException
     */
    @Test
    public void testListFile() throws FileNotFoundException, IllegalArgumentException, IOException {
        RemoteIterator<LocatedFileStatus> listFiles = fileSystem.listFiles(new Path("/"), true);
        while (listFiles.hasNext()) {
            System.out.println(listFiles.next().getPath().getName());
        }
    }

}

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