Hadoop入门：HDFS的API操作

一、运行前提

已经搭建好全分布式hadoop集群

二、hdfs实例代码

package com.psn.hdfs;


import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.*;
import org.checkerframework.dataflow.qual.TerminatesExecution;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;

import java.io.IOException;
import java.net.URI;
import java.net.URISyntaxException;
import java.util.Arrays;

/**
 * @author psn
 * @version 1.0
 * @date 2021/11/24 21:06
 */
public class HdfsClient {
    
    
    FileSystem fs;
    @Before
    public void before() throws URISyntaxException, IOException, InterruptedException {
    
    
        URI uri = new URI("hdfs://hadoop102:8020");
        Configuration configuration = new Configuration();
        configuration.set("dfs.replication","3");
        String user = "centos7";
        fs = FileSystem.get(uri, configuration, user);
    }
    @After
    public void after() throws IOException {
    
    
        fs.close();
    }

    /**
     * 新建文件
     * @throws URISyntaxException
     */
    @Test
    public void testMkdir() throws URISyntaxException, IOException {
    
    
        fs.mkdirs(new Path("/zs"));
    }

    /** 上传文件
     * 参数优先级
     * hdfs-default.xml => hdfs-site.xml=> 在项目资源目录下的配置文件 =》代码里面的配置
     *
     * @throws IOException
     */
    @Test
    public void testput() throws IOException {
    
    
        fs.copyFromLocalFile(false,true,new Path("d://tools/node-v14.16.0-x64.msi"),new Path("/zs"));
    }
    /** 下载文件
     * @author psn
     * @date 2021/11/25
     * @param
     * @return
     */
    @Test
    public void downFile() throws IOException {
    
    
        // 参数的解读：参数一：原文件是否删除；参数二：原文件路径HDFS； 参数三：目标地址路径Win ; 参数四：false：做crc校验，true：无需做crc校验
        //fs.copyToLocalFile(false,new Path("/zs"),new Path("D://"),true);
        fs.copyToLocalFile(false,new Path("/zs"),new Path("D://"),false);
    }
    /**重命名和移动
     * @author psn
     * @date 2021/11/25
     * @param
     * @return
     */
    @Test
    public void rename() throws IOException {
    
    
        //fs.rename(new Path("/zs"), new Path("/lisi"));
        //fs.rename(new Path("/zs/node-v14.16.0-x64.msi"),new Path("/zs/node-v14.16.0-x641.msi"));
        fs.rename(new Path("/zs/node-v14.16.0-x641.msi"),new Path("/wcinput/node-v14.16.0-x64.msi"));
    }
    /** 获取文件详情
     * @author psn
     * @date 2021/11/25
     * @param
     * @return
     */
    @Test
    public void testDetailFile() throws IOException {
    
    
        RemoteIterator<LocatedFileStatus> listFiles = fs.listFiles(new Path("/wcinput"), true);
        while (listFiles.hasNext()){
    
    
            LocatedFileStatus fileStatus = listFiles.next();
            System.out.println("=================="+fileStatus.getPath().getName()+"=========================");
            System.out.println(fileStatus.isFile());
            System.out.println(fileStatus.getOwner());
            System.out.println(fileStatus.getPermission());
            System.out.println(fileStatus.getLen());
            BlockLocation[] blockLocations = fileStatus.getBlockLocations();
            System.out.println(Arrays.asList(blockLocations));
        }
    }
    /** 删除文件
     * @author psn
     * @date 2021/11/25
     * @param
     * @return
     */
    public void TestDel() throws IOException {
    
    
        //参数解读：参数1：要删除的路径； 参数2 ： 是否递归删除
        fs.delete(new Path("/zs"),true);
    }
}