大数据学习之HDFS基本API操作（下）06

　　　　　　　　　　　　　　　　　　hdfs文件流操作方法一：

package it.dawn.HDFSPra;

import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.URI;
import java.net.URISyntaxException;

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.zookeeper.common.IOUtils;
import org.junit.Before;
import org.junit.Test;

/**
 * @version 1.0
 * @author Dawn
 * @date 2019年4月28日22:28:53
 * @return hdfs的读写操作。顺便练习一下java的IO操作
 */
public class HdfsReadData02 {

    public static FileSystem fs=null;
    public static String hdfs="hdfs://bigdata11:9000";

    @Before
    public void init() throws IOException, InterruptedException, URISyntaxException {
        //其实这一句我也不是很清楚。不加这个有个异常，我看起来感觉很恶心。不过没有影响。大家加不加都没问题
        System.setProperty("hadoop.home.dir", "E:\\hadoop2.7.3\\hadoop-2.7.3");
        //1 加载配置
        Configuration conf=new Configuration();
        //2 构造客服端
        fs=FileSystem.get(new URI(hdfs), conf, "root");
    }

    //读数据方式1
    @Test
    public void testReadData1() throws IllegalArgumentException, IOException {
        //1 拿到流
        //其实和这个没啥差别fs.copyToLocalFile(new Path("/xxx.txt"), new Path("f:/"));
        FSDataInputStream in=fs.open(new Path("/xxx.txt"));

        byte[] buf=new byte[1024];

        in.read(buf);

        //打印出来
        System.out.println(new String(buf));

        //记得关闭流
        in.close();
        fs.close();
    }

    //读数据方式2 （加了一个缓冲流而已）
    @Test
    public void testReadData2() throws IllegalArgumentException, IOException {
        //1 拿到流
        FSDataInputStream in=fs.open(new Path("/xxx.txt"));

        //2.缓冲流
        BufferedReader br=new BufferedReader(new InputStreamReader(in, "UTF-8"));

        //3.按行读取
        String line=null;

        //4:一行一行的读数据
        while((line=br.readLine()) != null) {
            //打印出来
            System.out.println(line);
        }

        //5.关闭资源
        br.close();
        in.close();
        fs.close();
    }

    /*
     * 读取hdfs中指定偏移量
     */
    @Test
    public void testRandomRead() throws IllegalArgumentException, IOException {
        //1：拿到流
        FSDataInputStream in= fs.open(new Path("/xxx.txt"));

        in.seek(3);

        byte[] b=new byte[5];

        in.read(b);

        System.out.println(new String(b));

        in.close();
        fs.close();
    }

    /**
     * 在hdfs中写数据 直接对存在的文件进行写操作
     * fs.creat(hdfsFilename,false)
     * @param Path f
     * @param boolean overwrite
     */
    @Test
    public void testWriteData() throws IllegalArgumentException, IOException {
        //拿到输出流
        FSDataOutputStream out=fs.create(new Path("/dawn.txt"),false);//第二个参数。是否覆盖

        //2.输入流
        FileInputStream in=new FileInputStream("f:/temp/a.txt");//其实我觉得new一个File好一点

        byte[] buf=new byte[1024];

        int read=0;

        while((read=in.read(buf)) != -1) { //the total number of bytes read into the buffer, or -1 if there is no more data because the end of the file has been reached.

            out.write(buf,0,read);
        }

        in.close();
        out.close();
        fs.close();
    }

    /*
     * 在hdfs中写数据 写一个新的数据
     */

    @Test
    public void testWriteData1() throws IllegalArgumentException, IOException {
        //1.创建输出流
        FSDataOutputStream out=fs.create(new Path("/haha"));

        //2.创建输入流
//        FileInputStream in=new FileInputStream(new File("f:/temp/data.txt"));//没啥用

        //3.写数据
        out.write("dawn will success".getBytes());

        //4.关闭资源
        IOUtils.closeStream(out);
        fs.close();
    }

}

　　　　　　　　　　　　　　　　　　　　　　hdfs文件流操作方法二：

package it.dawn.HDFSPra;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.net.URI;
import java.net.URISyntaxException;

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.junit.Before;
import org.junit.Test;

/**
 * @version 1.0
 * @author Dawn
 * @date 2019年4月28日23:21:03
 * @return 使用IOUtills更为方便
 */
public class HdfsIOUtilsTest {

    public static String hdfs="hdfs://bigdata11:9000";

    public static FileSystem fs=null;

    public static Configuration conf=null;

    @Before
    public void init() throws IOException, InterruptedException, URISyntaxException {

        conf =new Configuration();
        fs=FileSystem.get(new URI(hdfs), conf, "root");
    }

    /*
     * 文件上传HDFS
     *
     */
    @Test
    public void putFileToHDFS() throws IllegalArgumentException, IOException {
        //1.获取输入流
        FileInputStream fis=new FileInputStream(new File("f:/temp/lol.txt"));

        //2获取输出流
        FSDataOutputStream fos=fs.create(new Path("/dawn/n.txt"));

        //3 流的拷贝
        IOUtils.copyBytes(fis, fos, conf);

        //4.关闭资源
        IOUtils.closeStream(fis);
        IOUtils.closeStream(fos);
    }

    /*
     * 文件下载HDFS
     */
    @Test
    public void getFileFromHDFS() throws IllegalArgumentException, IOException {
        //1.获取输入流
        FSDataInputStream fis=fs.open(new Path("/xxx.txt"));

        //2.获取输出流
        FileOutputStream fos=new FileOutputStream("f:/temp/lala.txt");

        //3.流的对拷
        IOUtils.copyBytes(fis, fos, conf);

        //4.关闭资源
        IOUtils.closeStream(fos);
        IOUtils.closeStream(fis);
    }

}

附上读写流程图