HDFS的文件操作

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HDFS的文件操作
格式化HDFS
命令：user@namenode:hadoop$ bin/hadoop namenode -format
启动HDFS
命令：user@namenode:hadoop$ bin/start-dfs.sh

列出HDFS上的文件

命令：user@namenode:hadoop$ bin/hadoop dfs -ls

使用hadoop API

Java代码

public List<String[]> GetFileBolckHost(Configuration conf, String FileName) {
try {
List<String[]> list = new ArrayList<String[]>();
FileSystem hdfs = FileSystem.get(conf);
Path path = new Path(FileName);
FileStatus fileStatus = hdfs.getFileStatus(path);
BlockLocation[] blkLocations = hdfs.getFileBlockLocations(
fileStatus, 0, fileStatus.getLen());
int blkCount = blkLocations.length;
for (int i = 0; i < blkCount; i++) {
String[] hosts = blkLocations[i].getHosts();
list.add(hosts);
}
return list;
} catch (IOException e) {
e.printStackTrace();
}
return null;
}

在HDFS上创建目录
命令：user@namenode:hadoop$ bin/hadoop dfs -mkdir /文件名

使用hadoop API

Java代码

// 在HDFS新建文件
public FSDataOutputStream CreateFile(Configuration conf, String FileName) {
try {
FileSystem hdfs = FileSystem.get(conf);
Path path = new Path(FileName);
FSDataOutputStream outputStream = hdfs.create(path);
return outputStream;
} catch (IOException e) {
e.printStackTrace();
}
return null;
}

上传一个文件到HDFS
命令：user@namenode:hadoop$ bin/hadoop dfs -put 文件名 /user/yourUserName/

使用hadoop API

Java代码

// 上传文件到HDFS
public void PutFile(Configuration conf, String srcFile, String dstFile) {
try {
FileSystem hdfs = FileSystem.get(conf);
Path srcPath = new Path(srcFile);
Path dstPath = new Path(dstFile);
hdfs.copyFromLocalFile(srcPath, dstPath);
} catch (IOException e) {
e.printStackTrace();
}
}

从 HDFS 中导出数据

命令：user@namenode:hadoop$ bin/hadoop dfs -cat foo

使用hadoop API

Java代码

// 从HDFS读取文件
public void ReadFile(Configuration conf, String FileName) {
try {
FileSystem hdfs = FileSystem.get(conf);
FSDataInputStream dis = hdfs.open(new Path(FileName));
IOUtils.copyBytes(dis, System.out, 4096, false);
dis.close();
} catch (IOException e) {
e.printStackTrace();
}
}

HDFS 的关闭
命令：user@namenode:hadoop$ bin/stop-dfs.sh

HDFS全局状态信息

命令：bin/hadoop dfsadmin -report

我们可以得到一份全局状态报告。这份报告包含了HDFS集群的基本信息，当然也有每台机器的一些情况。

以上讲的都是本地操作HDFS，都是基于在ubuntu下并配置有hadoop环境下对HDFS的操作，作为客户端也可以在window系统下远程的对 HDFS进行操作，其实原理基本上差不多，只需要集群中namenode对外开放的IP和端口，就可以访问到HDFS

Java代码

/**
* 对HDFS操作
* @author yujing
*
*/
public class Write {
public static void main(String[] args) {
try {
uploadTohdfs();
readHdfs();
getDirectoryFromHdfs();
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
public static void uploadTohdfs() throws FileNotFoundException, IOException {
String localSrc = "D://qq.txt";
String dst = "hdfs://192.168.1.11:9000/usr/yujing/test.txt";
InputStream in = new BufferedInputStream(new FileInputStream(localSrc));
Configuration conf = new Configuration();
FileSystem fs = FileSystem.get(URI.create(dst), conf);
OutputStream out = fs.create(new Path(dst), new Progressable() {
public void progress() {
System.out.println(".");
}
});
System.out.println("上传文件成功");
IOUtils.copyBytes(in, out, 4096, true);
}
/** 从HDFS上读取文件 */
private static void readHdfs() throws FileNotFoundException, IOException {
String dst = "hdfs://192.168.1.11:9000/usr/yujing/test.txt";
Configuration conf = new Configuration();
FileSystem fs = FileSystem.get(URI.create(dst), conf);
FSDataInputStream hdfsInStream = fs.open(new Path(dst));
OutputStream out = new FileOutputStream("d:/qq-hdfs.txt");
byte[] ioBuffer = new byte[1024];
int readLen = hdfsInStream.read(ioBuffer);
while (-1 != readLen) {
out.write(ioBuffer, 0, readLen);
readLen = hdfsInStream.read(ioBuffer);
}
System.out.println("读文件成功");
out.close();
hdfsInStream.close();
fs.close();
}
/**
* 以append方式将内容添加到HDFS上文件的末尾;注意：文件更新，需要在hdfs-site.xml中添<property><name>dfs.
* append.support</name><value>true</value></property>
*/
private static void appendToHdfs() throws FileNotFoundException,
IOException {
String dst = "hdfs://192.168.1.11:9000/usr/yujing/test.txt";
Configuration conf = new Configuration();
FileSystem fs = FileSystem.get(URI.create(dst), conf);
FSDataOutputStream out = fs.append(new Path(dst));
int readLen = "zhangzk add by hdfs java api".getBytes().length;
while (-1 != readLen) {
out.write("zhangzk add by hdfs java api".getBytes(), 0, readLen);
}
out.close();
fs.close();
}
/** 从HDFS上删除文件 */
private static void deleteFromHdfs() throws FileNotFoundException,
IOException {
String dst = "hdfs://192.168.1.11:9000/usr/yujing";
Configuration conf = new Configuration();
FileSystem fs = FileSystem.get(URI.create(dst), conf);
fs.deleteOnExit(new Path(dst));
fs.close();
}
/** 遍历HDFS上的文件和目录 */
private static void getDirectoryFromHdfs() throws FileNotFoundException,
IOException {
String dst = "hdfs://192.168.1.11:9000/usr/yujing";
Configuration conf = new Configuration();
FileSystem fs = FileSystem.get(URI.create(dst), conf);
FileStatus fileList[] = fs.listStatus(new Path(dst));
int size = fileList.length;
for (int i = 0; i < size; i++) {
System.out.println("文件名name:" + fileList[i].getPath().getName()
+ "文件大小/t/tsize:" + fileList[i].getLen());
}
fs.close();
}
}