java 简单操作HDFS

创建java 项目

package com.yw.hadoop273;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.*;
import org.apache.hadoop.io.IOUtils;
import org.junit.Test;

import java.io.ByteArrayOutputStream;
import java.io.InputStream;
import java.net.URL;
import java.net.URLConnection;

/**
 * 完成hdfs操作
 * @Auther: YW
 * @Date: 2019/9/11 21:51
 * @Description:
 */
public class TestHdfs {
    /**
     * 读取hdfs文件
     */
    @Test
    public void readFile() throws Exception{
        //注册url流处理器工厂(hdfs)
        URL.setURLStreamHandlerFactory(new FsUrlStreamHandlerFactory());

        URL url = new URL("hdfs://http://192.168.248.129:8020/usr/local/hadoop/core-site.xml");
        URLConnection conn = url.openConnection();
        InputStream is = conn.getInputStream();
        byte[] buf = new byte[is.available()];
        is.read(buf);
        is.close();
        String str = new String(buf);
        System.out.println(str);
    }

    /**
     * 通过hadoop API访问文件
     */
    @Test
    public void readFileByAPI() throws Exception{
        Configuration conf = new Configuration();
        conf.set("fs.defaultFS", "hdfs://192.168.248.129:8020/");
        FileSystem fs = FileSystem.get(conf) ;
        Path p = new Path("/usr/local/hadoop/core-site.xml");
        FSDataInputStream fis = fs.open(p);
        byte[] buf = new byte[1024];
        int len = -1 ;

        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        while((len = fis.read(buf)) != -1){
            baos.write(buf, 0, len);
        }
        fis.close();
        baos.close();
        System.out.println(new String(baos.toByteArray()));
    }
    /**
     * 通过hadoop API访问文件
     */
    @Test
    public void readFileByAPI2() throws Exception{
        Configuration conf = new Configuration();
        conf.set("fs.defaultFS", "hdfs://192.168.248.129:8020/");
        FileSystem fs = FileSystem.get(conf) ;
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        Path p = new Path("/usr/local/hadoop/core-site.xml");
        FSDataInputStream fis = fs.open(p);
        IOUtils.copyBytes(fis, baos, 1024);
        System.out.println(new String(baos.toByteArray()));
    }

    /**
     * mkdir 创建目录
     */
    @Test
    public void mkdir() throws Exception{
        Configuration conf = new Configuration();
        conf.set("fs.defaultFS", "hdfs://192.168.248.129:8020/");
        FileSystem fs = FileSystem.get(conf) ;
        fs.mkdirs(new Path("/usr/local/hadoop/myhadoop"));
    }

    /**
     * putFile 写文件
     */
    @Test
    public void putFile() throws Exception{
        Configuration conf = new Configuration();
        conf.set("fs.defaultFS", "hdfs://192.168.248.129:8020/");
        FileSystem fs = FileSystem.get(conf) ;
        FSDataOutputStream out = fs.create(new Path("/usr/local/hadoop/myhadoop/a.txt"));
        out.write("helloworld".getBytes());
        out.close();
    }

    /**
     * removeFile 删除目录 （注意权限）
     */
    @Test
    public void removeFile() throws Exception{
        Configuration conf = new Configuration();
        conf.set("fs.defaultFS", "hdfs://192.168.248.129:8020/");
        FileSystem fs = FileSystem.get(conf) ;
        Path p = new Path("/usr/local/hadoop/myhadoop");
        fs.delete(p, true);
    }
}

注意权限的修改

　　hdfs dfs -chmod 777 /usr/local/hadoop/

读到的内容

创建目录文件

完成。。