HDFS的运用

判断文件并删除文件

package com.doit.hdp.day01;
import com.doit.hdp.Utils;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;

public class Demo03 {
    public static void main(String[] args) throws Exception {
        FileSystem fs = Utils.getHdfsFs();
        Path path = new Path("/wnn");
        if(fs.exists(path)){
         fs.delete(path, true);

        }else{
            System.out.println("没有该文件无法删除");
        }
       fs.close();

    }
}

package com.doit.hdp.day01;
import com.doit.hdp.Utils;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
public class YiDong {
    public static void main(String[] args) throws Exception {
        FileSystem  fs= Utils.getHdfsFs();
        //移到已经存在的某个目录下
        fs.rename(new Path("/a.txt"),new Path("/user/a.txt"));
        //把目录名字进行改写
        fs.rename(new Path("/user"),new Path("/USER"));
        fs.close();
    }

}

查看命令如下：

[root@linux01 /]# hdfs dfs -ls /
Found 2 items
-rw-r--r--   3 root supergroup          0 2021-04-26 10:47 /jar.txt
drwxr-xr-x   - root supergroup          0 2021-04-26 20:16 /user
[root@linux01 /]# hdfs dfs -ls /user
Found 2 items
drwxr-xr-x   - root supergroup          0 2021-04-26 20:09 /user/a.txt
drwxr-xr-x   - root supergroup          0 2021-04-25 20:54 /user/root
[root@linux01 /]# hdfs dfs -ls /
Found 2 items
drwxr-xr-x   - root supergroup          0 2021-04-26 20:16 /USER
-rw-r--r--   3 root supergroup          0 2021-04-26 10:47 /jar.txt

package com.doit.hdp.day01;
import com.doit.hdp.Utils;
import org.apache.hadoop.fs.*;

import java.sql.Array;
import java.util.Arrays;

public class BianLi {
    public static void main(String[] args) throws Exception {
        FileSystem fs = Utils.getHdfsFs();
        //递归地去遍历这个文件系统的文件,不是文件夹哦，返回一个迭代器
        RemoteIterator<LocatedFileStatus> loca = fs.listFiles(new Path("/"),false);
        while(loca.hasNext()){
            LocatedFileStatus file = loca.next();
            Path path = file.getPath();
            String name = path.getName();
           // System.out.println(path+"----"+name);
            file.getBlockSize();//逻辑切块的大小  128M
            file.getReplication();//副本
            file.getLen();//实际长度
            BlockLocation[] bls = file.getBlockLocations();//实际的物理切块
            for (BlockLocation  bl:bls) {
                long length = bl.getLength();
                String[] hosts = bl.getHosts();
                //把数组转化成list集合
                System.out.println(path+"....."+length+",,"+ Arrays.asList(hosts));

            }

        }
        fs.close();
        //查看文件和文件夹
       // fs.listStatus();
    }
}

package com.doit.hdp.day01;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import java.net.URI;
public class Demo05 {
    public static void main(String[] args) throws Exception {
        Configuration conf = new Configuration();
        conf.set("dfs.replication","2");//自定义设置副本个数
        FileSystem fs = FileSystem.newInstance(new URI("hdfs://linux01:8020"), conf, "root");
        fs.copyFromLocalFile(new Path("d://text.rar"),new Path("/tt.rar"));
        fs.close();
    }
}

package com.doit.hdp.day01;
import com.doit.hdp.Utils;
import org.apache.hadoop.fs.FileStatus;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;

public class Demo06 {
    public static void main(String[] args) throws Exception {
        FileSystem fs = Utils.getHdfsFs();
        //遍历文件和文件夹
        FileStatus[] fileStatuses = fs.listStatus(new Path("/"));
        for (FileStatus  fileStatuse: fileStatuses
             ) {
            Path path = fileStatuse.getPath();
            String name = path.getName();
            System.out.println(path);
            System.out.println(name);

        }
        
        fs.close();
    }
}

package com.doit.hdp.day01;
import com.doit.hdp.Utils;
import org.apache.hadoop.fs.FSDataInputStream;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import java.io.BufferedReader;
import java.io.InputStreamReader;
public class Demo07 {
    public static void main(String[] args) throws Exception {
        FileSystem fs = Utils.getHdfsFs();
        FSDataInputStream is = fs.open(new Path("/m.txt"));
        is.skip(20);
        BufferedReader br = new BufferedReader(new InputStreamReader(is));

        String s = br.readLine();
        System.out.println(s);
        br.close();
        is.close();
        fs.close();


    }
}