1、重读配置文件core-site.xml

< xml version="1.0" >

< xml-stylesheet type="text/xsl" href="configuration.xsl" >

hadoop.tmp.dir

/home/zhangzk/hadoop

A base for other temporary directories.

fs.default.name

hdfs://linux-zzk-113:9000

配置项：hadoop.tmp.dir表示命名节点上存放元数据的目录位置，对于数据节点则为该节点上存放文件数据的目录。

配置项：fs.default.name表示命名的IP地址和端口号,缺省值是file:///，对于JavaAPI来讲，连接HDFS必须使用这里的配置的URL地址，对于数据节点来讲，数据节点通过该URL来访问命名节点。

2、利用JavaAPI来访问HDFS的文件与目录

package com.demo.hdfs;

import java.io.BufferedInputStream;

import java.io.FileInputStream;

import java.io.FileNotFoundException;

import java.io.FileOutputStream;

import java.io.IOException;

import java.io.InputStream;

import java.io.OutputStream;

import java.net.URI;

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;

import org.apache.hadoop.io.IOUtils;

import org.apache.hadoop.util.Progressable;

/**

* @author zhangzk

*

*/

public class FileCopyToHdfs {

public static void main(String[] args) throws Exception {

try {

//uploadToHdfs();

//deleteFromHdfs();

//getDirectoryFromHdfs();

appendToHdfs();

readFromHdfs();

} catch (Exception e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

finally

{

System.out.println("SUCCESS");

}

}

/**上传文件到HDFS上去*/

private static void uploadToHdfs() throws FileNotFoundException,IOException {

String localSrc = "d://qq.txt";

String dst = "hdfs://192.168.0.113:9000/user/zhangzk/qq.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.print(".");

}

});

IOUtils.copyBytes(in, out, 4096, true);

}

/**从HDFS上读取文件*/

private static void readFromHdfs() throws FileNotFoundException,IOException {

String dst = "hdfs://192.168.0.113:9000/user/zhangzk/qq.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);

}

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dfs.append.supporttrue*/

private static void appendToHdfs() throws FileNotFoundException,IOException {

String dst = "hdfs://192.168.0.113:9000/user/zhangzk/qq.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://192.168.0.113:9000/user/zhangzk/qq-bak.txt";

Configuration conf = new Configuration();