1、引入jar，引入核心和hdfs有关所有包
2、实例代码：
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.Scanner;import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FSDataInputStream;
import org.apache.hadoop.fs.FSDataOutputStream;
import org.apache.hadoop.fs.FileStatus;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IOUtils;/**
* 云盘的核心实现
* @author hadoop
*
*/
public class CloudDisk {
public static void main(String[] args){
System.out.println("请输入你想进行的操作：\n\tls --查看目录下的文件和子目录\n\t"
+ "cat --查看文件内容\n\t"
+ "mkdir --创建目录\n\t"
+ "rm --删除文件或者空目录\n\t"
+ "rmr --删除文件或者目录\n\t"
+ "put --将本地文件上传到HDFS\n\t"
+ "get --将HDFS上的文件下载到本地\n");
Scanner scanner = new Scanner(System.in);
CloudDisk cd = new CloudDisk();
while(true){
String operation = scanner.nextLine();
if("exit".equalsIgnoreCase(operation)){
System.out.println("退出操作界面");
break;
}else if("ls".equalsIgnoreCase(operation)){
System.out.println("请指定文件或目录的路径：");
String path = scanner.nextLine();
cd.listFiles(path);
}else if("cat".equalsIgnoreCase(operation)){
System.out.println("请指定要查看内容的文件：");
String file = scanner.nextLine();
cd.cat(file);
}else if("mkdir".equalsIgnoreCase(operation)){
System.out.println("Create directory or file , give me the path:");
String file = scanner.nextLine();
cd.mkdir(file);
}else if("rm".equalsIgnoreCase(operation)){
String file = scanner.nextLine();
cd.rm(file, false);
}else if("rmr".equalsIgnoreCase(operation)){
String file = scanner.nextLine();
cd.rm(file, true);
}else if("put".equalsIgnoreCase(operation)){
String file = scanner.nextLine();
cd.put("/home/hadoop/wc2.input", "/user/hadoop/mapreduce/input/wc2.input");
}else if("get".equalsIgnoreCase(operation)){
cd.get("/opt/modules/hadoop/hadoop-2.5.0/" ,"/test.txt" );
}else{
scanner.close();
throw new RuntimeException("未知的操作指令");
}
}
scanner.close();
}/**
* ls
*/
public void listFiles(String specialPath){
Configuration conf = new Configuration();
conf.set("fs.defaultFS", "hdfs://192.168.1.120:8020/");
FileSystem fileSystem = null;
try {
fileSystem = FileSystem.get(conf);
FileStatus[] fstats = fileSystem.listStatus(new Path(specialPath));
for(FileStatus fstat : fstats){
System.out.println(fstat.isDirectory()?"directory":"file");
System.out.println("Permission:" + fstat.getPermission());
System.out.println("Owner:" + fstat.getOwner());
System.out.println("Group:" + fstat.getGroup());
System.out.println("Size:" + fstat.getLen());
System.out.println("Replication:" + fstat.getReplication());
System.out.println("Block Size:" + fstat.getBlockSize());
System.out.println("Name:" + fstat.getPath());
System.out.println("#############################");
}
} catch (IOException e) {
e.printStackTrace();
System.err.println("link err");
}finally{
if(fileSystem != null){
try {
fileSystem.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
/**
* cat
* @param hdfsFilePath
*/
public void cat(String hdfsFilePath){
Configuration conf = new Configuration();
conf.set("fs.defaultFS", "hdfs://192.168.1.120:8020/");
FileSystem fileSystem = null;
try {
fileSystem = FileSystem.get(conf);
FSDataInputStream fdis = fileSystem.open(new Path("/test.txt"));
IOUtils.copyBytes(fdis, System.out, 1024);
} catch (IOException e) {
e.printStackTrace();
}finally{
IOUtils.closeStream(fileSystem);
}
}
/**
* 创建目录
* @param hdfsFilePath
*/
public void mkdir(String hdfsFilePath){
FileSystem fileSystem = this.getFS();
try {
boolean success = fileSystem.mkdirs(new Path(hdfsFilePath));
if(success){
System.out.println("Create directory or file successfully");
}
} catch (IllegalArgumentException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}finally{
this.closeFS(fileSystem);
}
}
/**
* 删除文件或目录
* @param hdfsFilePath
* @param recursive
*/
public void rm(String hdfsFilePath,boolean recursive){
FileSystem fileSystem = this.getFS();
try {
boolean success = fileSystem.delete(new Path(hdfsFilePath), recursive);
if(success){
System.out.println("delete successfully");
}
} catch (IllegalArgumentException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}finally{
this.closeFS(fileSystem);
}
}
/**
* 上传文件到HDFS
* @param localFilePath
* @param hdfsFilePath
*/
public void put(String localFilePath,String hdfsFilePath){
FileSystem fileSystem = this.getFS();
try {
FSDataOutputStream fdos = fileSystem.create(new Path(hdfsFilePath));
FileInputStream fis = new FileInputStream(new File(localFilePath));
IOUtils.copyBytes(fis, fdos, 1024);
} catch (IllegalArgumentException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}finally{
IOUtils.closeStream(fileSystem);
}
}
/**
* 下载文件到本地
* @param localFilePath
* @param hdfsFilePath
*/
public void get(String localFilePath,String hdfsFilePath){
FileSystem fileSystem = this.getFS();
try {
FSDataInputStream fsis = fileSystem.open(new Path(hdfsFilePath));
FileOutputStream fos = new FileOutputStream(new File(localFilePath));
IOUtils.copyBytes(fsis, fos, 1024);
} catch (IllegalArgumentException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}finally{
IOUtils.closeStream(fileSystem);
}
}
/**
* 获取FileSystem实例
* @return
*/
private FileSystem getFS(){
Configuration conf = new Configuration();
conf.set("fs.defaultFS", "hdfs://192.168.1.120:8020");
System.setProperty("HADOOP_USER_NAME", "hadoop2");
FileSystem fileSystem = null;
try {
fileSystem = FileSystem.get(conf);
return fileSystem;
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
/**
* 关闭FileSystem
* @param fileSystem
*/
private void closeFS(FileSystem fileSystem){
if(fileSystem != null){
try {
fileSystem.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}