FileSystem fs = FileSystem.get(new URI(path),new Configuration())
fsin = fs.open(new Path(path))
IOUtils.copyBytes(fsin, System.out, 1024,true)
数据库里存放文件路径的表中再添加一个字段表示资源名称不就尺祥兄行了。下载陵袭时用户提交带有资源名称参数的请求，收到请求后根据请求的宴轮资源名称参数去数据库查询文件的实际位置和名称，然后用文件的实际路径和名称 读取文件 得到inputstream流，把文件的inputstream写入给用户响应的response的outputstream就行了。
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("销仔/user/hadoop/data/20140318")
boolean result = fs.mkdirs(dir)// 创建文件夹
System.out.println("make dir :" + result)
//晌谈 创建文件，并写入内容
Path dst = new Path("/user/hadoop/data/20140318/tmp")
byte[] buff = "hello,hadoop!"宴斗碰.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)
}
}
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