package cn.com.fri.hadoop;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.net.URI;
import java.util.Date;
import org.apache.hadoop.fs.FSDataInputStream;
import org.apache.hadoop.fs.FileContext;
import org.apache.hadoop.fs.FileStatus;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.fs.UnsupportedFileSystemException;
import org.apache.hadoop.io.IOUtils;
import org.apache.hadoop.security.AccessControlException;
/**
* 读取文件内容以及文件信息
* @author alex
*
*/
public class MainRead {
public static void main(String[] args) throws AccessControlException, FileNotFoundException, UnsupportedFileSystemException, IOException {
FileContext fc = FileContext.getFileContext(URI.create("hdfs://localhost:9000"));
FSDataInputStream fsInput = fc.open(new Path("test"));
IOUtils.copyBytes(fsInput, System.out, 4090,false);
FileStatus status = fc.getFileStatus(new Path("test"));
System.out.println("--File status---");
System.out.println(new Date(status.getAccessTime()));
System.out.println(status.getPath().toUri().getPath());
double i = 1024.00;
Double len = new Double(status.getLen());
len = len/i;
System.out.println("File length:"+len+"kb");
System.out.println("Block size:"+status.getBlockSize()/1024/1024+"mb");
System.out.println(status.getOwner());
}
}

package cn.com.fri.hadoop;
import java.io.BufferedInputStream;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.net.URI;
import java.util.EnumSet;
import org.apache.hadoop.fs.CreateFlag;
import org.apache.hadoop.fs.FSDataOutputStream;
import org.apache.hadoop.fs.FileAlreadyExistsException;
import org.apache.hadoop.fs.FileContext;
import org.apache.hadoop.fs.ParentNotDirectoryException;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IOUtils;
import org.apache.hadoop.security.AccessControlException;
/**
* 创建一个文件
* @author alex
*
*/
public class MainCreate {
public static void main(String[] args) throws AccessControlException, FileAlreadyExistsException, FileNotFoundException, ParentNotDirectoryException, IOException {
FileContext fc = FileContext.getFileContext(URI.create("hdfs://localhost:9000"));
EnumSet<CreateFlag> es = EnumSet.noneOf(CreateFlag.class);
es.add(CreateFlag.CREATE);
FSDataOutputStream out = fc.create(new Path("test"), es);
InputStream in = new BufferedInputStream(new FileInputStream("/Users/alex/Desktop/persons.rtf"));
IOUtils.copyBytes(in, out, 4090,true);
}
}

在new Path的时候，文件如果加上/则代表放入根路径，否则放入/user/name/路径下，如果hdfs中不存在此路径，则抛出父目录不存在的异常。

知识点

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