hadoop学习(五)----HDFS的java操作

前面我们基本学习了HDFS的原理，hadoop环境的搭建，下面开始正式的实践，语言以java为主。这一节来看一下HDFS的java操作。

1 环境准备#

上一篇说了windows下搭建hadoop环境，开始之前先启动hadoop。我本地的编译器是idea。搭建maven工程：

pom.xml文件：

<dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.12</version>
      <scope>test</scope>
    </dependency>

    <dependency>
      <groupId>org.apache.hadoop</groupId>
      <artifactId>hadoop-common</artifactId>
      <version>2.7.3</version>
    </dependency>
    <dependency>
      <groupId>org.apache.hadoop</groupId>
      <artifactId>hadoop-hdfs</artifactId>
      <version>2.7.3</version>
    </dependency>


    <dependency>
      <groupId>org.apache.hadoop</groupId>
      <artifactId>hadoop-mapreduce-client-core</artifactId>
      <version>2.7.3</version>
    </dependency>

    <dependency>
      <groupId>org.apache.hadoop</groupId>
      <artifactId>hadoop-mapreduce-client-jobclient</artifactId>
      <version>2.7.3</version>
    </dependency>

    <dependency>
      <groupId>log4j</groupId>
      <artifactId>log4j</artifactId>
      <version>1.2.17</version>
    </dependency>
</dependencies>

新建测试类：FileOperator.java

import org.apache.commons.compress.utils.IOUtils;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.*;
import org.apache.hadoop.fs.permission.FsPermission;
import org.apache.hadoop.hdfs.DistributedFileSystem;
import org.junit.Before;
import org.junit.Test;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.net.URI;
import java.text.SimpleDateFormat;
import java.util.Date;

/**
 * Created by Administrator on 2017/12/3.
 */
public class FileOperator {
    private static final Logger logger = LoggerFactory.getLogger(FileOperator.class);

    public static DistributedFileSystem dfs=null;
    public static String nameNodeUri="hdfs://localhost:9000";

    @Before
    public void initFileSystem() throws Exception{
        logger.info("initial hadoop env----");
        dfs=new DistributedFileSystem();
        dfs.initialize(new URI(nameNodeUri), new Configuration());
        logger.info("connection is successful");
        Path workingDirectory = dfs.getWorkingDirectory();
        System.out.println("current workspace is ："+workingDirectory);
    }
    /**
     * 创建文件夹
     * @throws Exception
     */
    @Test
    public void testMkDir() throws Exception{
        boolean res = dfs.mkdirs(new Path("/test/aaa/bbb"));
        System.out.println("目录创建结果："+(res?"创建成功":"创建失败"));
    }
    /**
     * 删除目录/文件
     * @throws Exception
     */
    @Test
    public void testDeleteDir() throws Exception{
        dfs.delete(new Path("/test/aaa/bbb"), false);
    }

    /**
     * 获取指定目录下所有文件(忽略目录)
     * @throws Exception
     * @throws IllegalArgumentException
     */
    @Test
    public void testFileList() throws Exception{
        RemoteIterator<LocatedFileStatus> listFiles = dfs.listFiles(new Path("/"), true);
        SimpleDateFormat sdf=new SimpleDateFormat("yyyy-MM-dd HH:mm:ss.SSS");
        while (listFiles.hasNext()) {
            LocatedFileStatus fileStatus = (LocatedFileStatus) listFiles.next();
            //权限
            FsPermission permission = fileStatus.getPermission();
            //拥有者
            String owner = fileStatus.getOwner();
            //组
            String group = fileStatus.getGroup();
            //文件大小byte
            long len = fileStatus.getLen();
            long modificationTime = fileStatus.getModificationTime();
            Path path = fileStatus.getPath();
            System.out.println("-------------------------------");
            System.out.println("permission:"+permission);
            System.out.println("owner:"+owner);
            System.out.println("group:"+group);
            System.out.println("len:"+len);
            System.out.println("modificationTime:"+sdf.format(new Date(modificationTime)));
            System.out.println("path:"+path);
        }
    }
    /**
     * 【完整】文件上传
     * 注意：文件上传在Window开发环境下，使用apache-common提供的<code>org.apache.commons.io.IOUtils.copy</code>可能存在问题
     */
    @Test
    public void testUploadFullFile() throws Exception{
        FSDataOutputStream out = dfs.create(new Path("/test/aaa/testFile.txt"), true);
        InputStream in = new FileInputStream("F:\\test\\cluster\\input\\testFile.txt");
        IOUtils.copy(in, out);
        System.out.println("上传完毕");
    }


    /**
     * 【分段|部分】文件上传
     * 注意：文件上传在Window开发环境下，使用apache-common提供的<code>org.apache.commons.io.IOUtils.copy</code>可能存在问题
     */
    @Test
    public void testUploadFile2() throws Exception{
        FSDataOutputStream out = dfs.create(new Path("/test/aaa/testFile1.txt"), true);
        InputStream in = new FileInputStream("F:\\test\\cluster\\input\\testFile.txt");
        org.apache.commons.io.IOUtils.copyLarge(in, out, 6, 12);
        System.out.println("上传完毕");
    }
    /**
     * 【完整】下载文件
     * 注意：windows开发平台下，使用如下API
     */
    @Test
    public void testDownloadFile() throws Exception{
        //使用Java API进行I/O,设置useRawLocalFileSystem=true
        dfs.copyToLocalFile(false,new Path("/test/aaa/testFile.txt"),
                new Path("E:/"),true);
        System.out.println("下载完成");
    }

    /**
     * 【部分】下载文件
     */
    @Test
    public void testDownloadFile2() throws Exception{
        //使用Java API进行I/O,设置useRawLocalFileSystem=true
        FSDataInputStream src = dfs.open(new Path("/test/aaa/testFile.txt"));
        FileOutputStream des = new FileOutputStream(new File("E:/","download_testFile.txt"));
        src.seek(6);
        org.apache.commons.io.IOUtils.copy(src, des);
        System.out.println("下载完成");
    }
}

代码如上，如要使用请调整相关目录。