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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$bin/hadoop dfs -ls
使用hadoop API
public List<String[]>GetFileBolckHost(Configuration conf, String FileName) {
try {
List<String[]> list = new ArrayList<String[]>();
FileSystem hdfs = FileSystem.get(conf);
Path path = new Path(FileName);
FileStatus fileStatus = hdfs.getFileStatus(path);
BlockLocation[] blkLocations = hdfs.getFileBlockLocations(
fileStatus, 0,fileStatus.getLen());
int blkCount = blkLocations.length;
for (int i = 0; i < blkCount; i++) {
String[] hosts =blkLocations.getHosts();
list.add(hosts);
}
return list;
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
在HDFS上创建目录
命令：user@namenode:hadoop$bin/hadoop dfs -mkdir /文件名
使用hadoop API
// 在HDFS新建文件
public FSDataOutputStream CreateFile(Configuration conf, StringFileName) {
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/hadoopdfs -put 文件名/user/yourUserName/
使用hadoop API
// 上传文件到HDFS
public voidPutFile(Configuration conf, String srcFile, String dstFile) {
try {
FileSystem hdfs =FileSystem.get(conf);
Path srcPath = newPath(srcFile);
Path dstPath = newPath(dstFile);
hdfs.copyFromLocalFile(srcPath, dstPath);
} catch (IOExceptione) {
e.printStackTrace();
}
}
从 HDFS 中导出数据
命令：user@namenode:hadoop$ bin/hadoopdfs -cat foo
使用hadoop API
// 从HDFS读取文件
public voidReadFile(Configuration conf, String FileName) {
try {
FileSystem hdfs =FileSystem.get(conf);
FSDataInputStreamdis = hdfs.open(new Path(FileName));
IOUtils.copyBytes(dis, System.out, 4096, false);
dis.close();
} catch (IOExceptione) {
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
/**
* 对HDFS操作
* @author yujing
*
*/
public class Write {
public static voidmain(String[] args) {
try {
uploadTohdfs();
readHdfs();
getDirectoryFromHdfs();
} catch(FileNotFoundException e) {
e.printStackTrace();
} catch (IOExceptione) {
e.printStackTrace();
}
}
public static voiduploadTohdfs() throws FileNotFoundException, IOException {
String localSrc ="D://qq.txt";
String dst ="hdfs://192.168.1.11:9000/usr/yujing/test.txt";
InputStream in = newBufferedInputStream(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 voidprogress() {
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 voidreadHdfs() 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);
FSDataInputStreamhdfsInStream = fs.open(new Path(dst));
OutputStream out = newFileOutputStream("d:/qq-hdfs.txt");
byte[] ioBuffer = newbyte[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 voidappendToHdfs() 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 voiddeleteFromHdfs() 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(newPath(dst));
fs.close();
}
/** 遍历HDFS上的文件和目录 */
private static voidgetDirectoryFromHdfs() 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.getPath().getName()
+ "文件大小/t/tsize:" +fileList.getLen());
}
fs.close();
}
}
我们可以通过http://主机IP：50030就可以查看集群的所有信息，也可以查看到自己上传到HDFS上的文件。
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原文地址：http://www.cnblogs.com/CRXY/p/4520355.html
