Hadoop基础教程-第4章 HDFS的Java API（4.7 Java API封装类）（

package cn.hadron.hdfsDemo;

import java.io.IOException;
import java.io.InputStream;
import java.net.URI;
import java.net.URISyntaxException;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IOUtils;
import org.apache.commons.lang.StringUtils;
/**
 * HDFS工具类
 * @author 程裕强
 * 
 */
public class HDFSUtil {

    /*
     * 获取文件系统
     */
    public static FileSystem getFileSystem(String url) {
        //StringUtils中方法的操作对象是java.lang.String类型的对象，是JDK提供的String类型操作方法的补充
        if(StringUtils.isBlank(url)){//判断某字符串是否为空或长度为0或由空白符(whitespace)构成 
            return null;
        }
        Configuration conf = new Configuration();
        FileSystem fs = null;
        try {
            URI uri = new URI(url.trim());
            fs = FileSystem.get(uri,conf);
        } catch (URISyntaxException|IOException e) {
            System.out.println(e);
        }
        return fs;
    }

    /*
     * 获取文件系统
     */
    public static FileSystem getFileSystem(String url,String user) {
        if(StringUtils.isBlank(url)){
            return null;
        }
        Configuration conf = new Configuration();
        FileSystem fs = null;
        try {
            URI uri = new URI(url.trim());
            fs = FileSystem.get(uri,conf,user);
        } catch (InterruptedException|URISyntaxException|IOException e) {
            System.out.println(e);
        }
        return fs;
    }

    /*
     * 创建目录
     */
    public static boolean mkdir(String path) throws Exception{
        FileSystem fs = getFileSystem(path,"root");
        boolean b=fs.mkdirs(new Path(path));
        fs.close();
        return b;
    }

    /**
     * 读文件
     * @param filePath
     * @throws IOException
     */
    public static void readFile(String filePath) throws IOException{
        FileSystem fs = getFileSystem(filePath);
        InputStream in=null;
        try{
            in=fs.open(new Path(filePath));
            IOUtils.copyBytes(in, System.out,4096,false);
        }catch(Exception e){
            System.out.println(e.getMessage());
        }finally{
            IOUtils.closeStream(in);
        }
    }

    /**
     * 上传文件
     * @param src
     * @param dst
     * @throws IOException
     */
    public static void putFile(String localPath,String hdfsPath) throws IOException{
        FileSystem fs = getFileSystem(hdfsPath,"root");
        fs.copyFromLocalFile(new Path(localPath), new Path(hdfsPath));
        fs.close();
    } 

    /**
     * 下载文件
     * @param hdfsPath
     * @param localPath
     * @throws IOException
     */
    public static void getFile(String hdfsPath,String localPath) throws IOException{
        FileSystem fs = getFileSystem(hdfsPath,"root");
        Path hdfs_path = new Path(hdfsPath);
        Path local_path = new Path(localPath);
        fs.copyToLocalFile(hdfs_path, local_path);
        fs.close();
    }

    /**
     * 递归删除
     * @param hdfsPath
     * @return
     * @throws IllegalArgumentException
     * @throws IOException
     */
    public static boolean deleteFile(String hdfsPath) throws IllegalArgumentException, IOException{
        FileSystem fs = getFileSystem(hdfsPath,"root");
        return fs.delete(new Path(hdfsPath), true);
    }

    /**
     * 目录列表
     * @param hdfsPath
     * @return
     */
    public static String[] listFile(String hdfsPath){
        String[] files = new String[0];
        FileSystem fs = getFileSystem(hdfsPath,"root");
        Path path=new Path(hdfsPath);
        FileStatus[] st=null;
        try {
            st = fs.listStatus(path);
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
        files = new String[st.length];
        for(int i=0;i<st.length;i++){
            files[i]=st[i].toString();
        }
        return files;
    }
    /**
     * 主方法，测试
     * @param args
     * @throws Exception
     */
    public static void main(String[] args) throws Exception{
        String base="hdfs://192.168.80.131:9000/";
        HDFSUtil.mkdir(base+"util");
        HDFSUtil.putFile("D:\\words", base+"util/");
        HDFSUtil.readFile(base+"util/words/words.txt");
        HDFSUtil.getFile(base+"util/words", "D:\\util");
        HDFSUtil.deleteFile(base+"abc");
    }

}

[root@node1 ~]# hdfs dfs -ls /
Found 2 items
drwxr-xr-x   - root supergroup          0 2017-05-14 09:40 /abc
drwxr-xr-x   - root supergroup          0 2017-05-14 09:37 /user

[root@node1 ~]# hdfs dfs -ls /
Found 2 items
drwxr-xr-x   - root supergroup          0 2017-05-14 09:37 /user
drwxr-xr-x   - root supergroup          0 2017-05-21 09:07 /util
[root@node1 ~]# hdfs dfs -ls /util/words
Found 2 items
-rw-r--r--   3 root supergroup         30 2017-05-21 09:18 /util/words/word2.txt
-rw-r--r--   3 root supergroup         55 2017-05-21 09:18 /util/words/words.txt

public static void main(String[] args) throws Exception{
        String base="hdfs://192.168.80.131:9000/";
    /*  HDFSUtil.mkdir(base+"util");
        HDFSUtil.putFile("D:\\words", base+"util/");
        HDFSUtil.readFile(base+"util/words/words.txt");
        HDFSUtil.getFile(base+"util/words", "D:\\util");
        HDFSUtil.deleteFile(base+"abc");*/
        String[] array=HDFSUtil.listFile(base);
        for(String s:array){
            System.out.println(s);
        }
    }

log4j:WARN No appenders could be found for logger (org.apache.hadoop.metrics2.lib.MutableMetricsFactory).
log4j:WARN Please initialize the log4j system properly.
log4j:WARN See http://logging.apache.org/log4j/1.2/faq.html#noconfig for more info.
FileStatus{path=hdfs://192.168.80.131:9000/user; isDirectory=true; modification_time=1494769072046; access_time=0; owner=root; group=supergroup; permission=rwxr-xr-x; isSymlink=false}
FileStatus{path=hdfs://192.168.80.131:9000/util; isDirectory=true; modification_time=1495372718309; access_time=0; owner=root; group=supergroup; permission=rwxr-xr-x; isSymlink=false}