例如，下面的代码演示了如何使用 listFiles() 方法来获取 HDFS 上的文件列表：
// 定义 HDFS 连接配置
Configuration conf = new Configuration()
// 获取 HDFS FileSystem 对象
FileSystem fs = FileSystem.get(conf)
// 定义要列举文件的目录
Path dirPath = new Path("/user/hadoop")
// 获取文件列表
RemoteIterator<LocatedFileStatus>fileIter = fs.listFiles(dirPath, true)
// 遍历文件列表
while (fileIter.hasNext()) {
// 获取当前文件信息
LocatedFileStatus fileStatus = fileIter.next()
// 输出文件名称和大小
System.out.println(fileStatus.getPath().getName() + " : " + fileStatus.getLen())
}
Java API读写HDFS
public class FSOptr {
/**
* @param args
*/
public static void main(String[] args) throws Exception {
// TODO Auto-generated method stub
Configuration conf = new Configuration()
makeDir(conf)
rename(conf)
delete(conf)
}
// 创建文件目录
private static void makeDir(Configuration conf) throws Exception {
FileSystem fs = FileSystem.get(conf)
Path dir = new Path("/user/hadoop/data/20140318")
boolean result = fs.mkdirs(dir)// 创建文件夹
System.out.println("make dir :" + result)
// 创建文件，并写入内容
Path dst = new Path("/user/hadoop/data/20140318/tmp")
byte[] buff = "hello,hadoop!".getBytes()
FSDataOutputStream outputStream = fs.create(dst)
outputStream.write(buff, 0, buff.length)
outputStream.close()
FileStatus files[] = fs.listStatus(dst)
for (FileStatus file : files) {
System.out.println(file.getPath())
}
fs.close()
}
// 重命名文件
private static void rename(Configuration conf) throws Exception {
FileSystem fs = FileSystem.get(conf)
Path oldName = new Path("/user/hadoop/data/20140318/1.txt")
Path newName = new Path("/user/hadoop/data/20140318/2.txt")
fs.rename(oldName, newName)
FileStatus files[] = fs.listStatus(new Path(
"/user/hadoop/data/20140318"))
for (FileStatus file : files) {
System.out.println(file.getPath())
}
fs.close()
}
// 删除文件
@SuppressWarnings("deprecation")
private static void delete(Configuration conf) throws Exception {
FileSystem fs = FileSystem.get(conf)
Path path = new Path("/user/hadoop/data/20140318")
if (fs.isDirectory(path)) {
FileStatus files[] = fs.listStatus(path)
for (FileStatus file : files) {
fs.delete(file.getPath())
}
} else {
fs.delete(path)
}
// 或者
fs.delete(path, true)
fs.close()
}
/**
* 下载,将hdfs文件下载到本地磁盘
*
* @param localSrc1
*本地的文件地址，即文件的路径
* @param hdfsSrc1
*存放在hdfs的文件地址
*/
public boolean sendFromHdfs(String hdfsSrc1, String localSrc1) {
Configuration conf = new Configuration()
FileSystem fs = null
try {
fs = FileSystem.get(URI.create(hdfsSrc1), conf)
Path hdfs_path = new Path(hdfsSrc1)
Path local_path = new Path(localSrc1)
fs.copyToLocalFile(hdfs_path, local_path)
return true
} catch (IOException e) {
e.printStackTrace()
}
return false
}
/**
* 上传，将本地文件copy到hdfs系统中
*
* @param localSrc
*本地的文件地址，即文件的路径
* @param hdfsSrc
*存放在hdfs的文件地址
*/
public boolean sendToHdfs1(String localSrc, String hdfsSrc) {
InputStream in
try {
in = new BufferedInputStream(new FileInputStream(localSrc))
Configuration conf = new Configuration()// 得到配置对象
FileSystem fs// 文件系统
try {
fs = FileSystem.get(URI.create(hdfsSrc), conf)
// 输出流，创建一个输出流
OutputStream out = fs.create(new Path(hdfsSrc),
new Progressable() {
// 重写progress方法
public void progress() {
// System.out.println("上传完一个设定缓存区大小容量的文件！")
}
})
// 连接两个流，形成通道，使输入流向输出流传输数据,
IOUtils.copyBytes(in, out, 10240, true)// in为输入流对象，out为输出流对象，4096为缓冲区大小，true为上传后关闭流
return true
} catch (IOException e) {
e.printStackTrace()
}
} catch (FileNotFoundException e) {
e.printStackTrace()
}
return false
}
/**
* 移动
*
* @param old_st原来存放的路径
* @param new_st移动到的路径
*/
public boolean moveFileName(String old_st, String new_st) {
try {
// 下载到服务器本地
boolean down_flag = sendFromHdfs(old_st, "/home/hadoop/文档/temp")
Configuration conf = new Configuration()
FileSystem fs = null
// 删除源文件
try {
fs = FileSystem.get(URI.create(old_st), conf)
Path hdfs_path = new Path(old_st)
fs.delete(hdfs_path)
} catch (IOException e) {
e.printStackTrace()
}
// 从服务器本地传到新路径
new_st = new_st + old_st.substring(old_st.lastIndexOf("/"))
boolean uplod_flag = sendToHdfs1("/home/hadoop/文档/temp", new_st)
if (down_flag &&uplod_flag) {
return true
}
} catch (Exception e) {
e.printStackTrace()
}
return false
}
// copy本地文件到hdfs
private static void CopyFromLocalFile(Configuration conf) throws Exception {
FileSystem fs = FileSystem.get(conf)
Path src = new Path("/home/hadoop/word.txt")
Path dst = new Path("/user/hadoop/data/")
fs.copyFromLocalFile(src, dst)
fs.close()
}
// 获取给定目录下的所有子目录以及子文件
private static void getAllChildFile(Configuration conf) throws Exception {
FileSystem fs = FileSystem.get(conf)
Path path = new Path("/user/hadoop")
getFile(path, fs)
}
private static void getFile(Path path, FileSystem fs)throws Exception {
FileStatus[] fileStatus = fs.listStatus(path)
for (int i = 0i <fileStatus.lengthi++) {
if (fileStatus[i].isDir()) {
Path p = new Path(fileStatus[i].getPath().toString())
getFile(p, fs)
} else {
System.out.println(fileStatus[i].getPath().toString())
}
}
}
//判断文件是否存在
private static boolean isExist(Configuration conf,String path)throws Exception{
FileSystem fileSystem = FileSystem.get(conf)
return fileSystem.exists(new Path(path))
}
//获取hdfs集群所有主机结点数据
private static void getAllClusterNodeInfo(Configuration conf)throws Exception{
FileSystem fs = FileSystem.get(conf)
DistributedFileSystem hdfs = (DistributedFileSystem)fs
DatanodeInfo[] dataNodeStats = hdfs.getDataNodeStats()
String[] names = new String[dataNodeStats.length]
System.out.println("list of all the nodes in HDFS cluster:")//print info
for(int i=0i <dataNodeStats.lengthi++){
names[i] = dataNodeStats[i].getHostName()
System.out.println(names[i])//print info
}
}
//get the locations of a file in HDFS
private static void getFileLocation(Configuration conf)throws Exception{
FileSystem fs = FileSystem.get(conf)
Path f = new Path("/user/cluster/dfs.txt")
FileStatus filestatus = fs.getFileStatus(f)
BlockLocation[] blkLocations = fs.getFileBlockLocations(filestatus,0,filestatus.getLen())
int blkCount = blkLocations.length
for(int i=0i <blkCounti++){
String[] hosts = blkLocations[i].getHosts()
//Do sth with the block hosts
System.out.println(hosts)
}
}
//get HDFS file last modification time
private static void getModificationTime(Configuration conf)throws Exception{
FileSystem fs = FileSystem.get(conf)
Path f = new Path("/user/cluster/dfs.txt")
FileStatus filestatus = fs.getFileStatus(f)
long modificationTime = filestatus.getModificationTime()// measured in milliseconds since the epoch
Date d = new Date(modificationTime)
System.out.println(d)
}
}
apache的Hadoop项目提供一类api可以通过java工程操作hdfs中的文件，包括：文件打开，读写，删除等、目录的创建，删除，读取目录中所有文件等。1、到http://hadoop.apache.org/releases.html下载Hadoop，解压后把所有jar加入项目的lib里
2、程序处理步骤： 1）得到Configuration对象，2）得到FileSystem对象，3）进行文件操作，简单示例如下：
/**
*
*/
package org.jrs.wlh
import java.io.IOException
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
/**
* @PutMeger.java
* java操作hdfs 往 hdfs中上传数据
* @version $Revision$</br>
* update: $Date$
*/
public class PutMeger {
public static void main(String[] args) throws IOException {
String[] str = new String[]{"E:\\hadoop\\UploadFileClient.java","hdfs://master:9000/user/hadoop/inccnt.java"}
Configuration conf = new Configuration()
FileSystem fileS= FileSystem.get(conf)
FileSystem localFile = FileSystem.getLocal(conf) //得到一个本地的FileSystem对象
Path input = new Path(str[0])//设定文件输入保存路径
Path out = new Path(str[1]) //文件到hdfs输出路径
try{
FileStatus[] inputFile = localFile.listStatus(input) //listStatus得到输入文件路径的文件列表
FSDataOutputStream outStream = fileS.create(out) //创建输出流
for (int i = 0i <inputFile.lengthi++) {
System.out.println(inputFile[i].getPath().getName())
FSDataInputStream in = localFile.open(inputFile[i].getPath())
byte buffer[] = new byte[1024]
int bytesRead = 0
while((bytesRead = in.read(buffer))>0){ //按照字节读取数据
System.out.println(buffer)
outStream.write(buffer,0,bytesRead)
}
in.close()
}
}catch(Exception e){
e.printStackTrace()
}
}
}
