相信大家通过之前的做法都已经搭建起了一个hadoop的开发环境。今天带大家通过java api来访问hdfs文件系统
首先启动hadoop集群
start-dfs.sh
或者
start-all.sh //一键启动hadoop集群和yarn集群
打开idea
在pom.xml文件里加入hadoop的依赖，我这里使用的是我搭建的一样版本的依赖
hadoop 2.7.3
2.7.3
org.apache.hadoop
hadoop-common
${hadoop.version}
org.apache.hadoop
hadoop-client
${hadoop.version}
org.apache.hadoop
hadoop-hdfs
${hadoop.version}
Java api在hdfs上创建一个文件目录
//创建配置文件
Configuration conf = new Configuration();
//windows下无法找到对应的环境变量，需要设置。把hadoop解压下来的根目录
System.setProperty("hadoop.home.dir", "F:\\linux\\hadoop-2.7.3");
// 指定hadoop fs的地址
conf.set("fs.defaultFS", "hdfs://master:9000");
//定义访问的根目录
String userRootPath = "/userSpace"
//拿到文件操作对象
FileSystem fs = FileSystem.get(conf);
//创建一个path对象，hdfs上的目录都需要用path对象来访问
Path dir = new Path(userRootPath); //表示根目录下的 userSpace目录
boolean result = fs.mkdirs(dir);
if(result){
System.out.println("创建目录成功！");
}
其实就和java访问文件一样的操作类似，非常简单，不过操作hdfs主要是通过FileSystem类。下面给大家贴一下完整代码
package com.mmcc.springboothadoop.hadoop;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.*;
import org.apache.hadoop.io.IOUtils;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
public class HdfsUtils {
private static Configuration conf = new Configuration();
public static String userRootPath = "/userSpace";
static {
//windows下无法找到对应的环境变量，需要设置
System.setProperty("hadoop.home.dir", "F:\\linux\\hadoop-2.7.3");
// 指定hadoop fs的地址
conf.set("fs.defaultFS", "hdfs://master:9000");
}
//判断路径是否存在
public static boolean exists(String path) throws IOException {
FileSystem fileSystem = FileSystem.get(conf);
return fileSystem.exists(new Path(path));
}
//创建文件
public static void createFile(String filePath, byte[] contents) throws IOException {
FileSystem fileSystem = FileSystem.get(conf);
Path path = new Path(filePath);
FSDataOutputStream fdo = fileSystem.create(path);
fdo.write(contents);
fdo.close();
fileSystem.close();
}
/**
* 创建文件
*
* @param filePath
* @param fileContent
* @throws IOException
*/
public static void createFile(String filePath, String fileContent)
throws IOException {
createFile(filePath, fileContent.getBytes());
}
//从本地复制到hdfs上
public static void copyFromLocalFile(String localFilePath, String remoteFilePath) throws IOException {
FileSystem fs = FileSystem.get(conf);
Path localPath = new Path(localFilePath);
Path remotePath = new Path(remoteFilePath);
fs.copyFromLocalFile(false, true, localPath, remotePath);
fs.close();
}
/**
* 删除目录或文件
*
* @param remoteFilePath
* @param recursive
* @return
* @throws IOException
*/
public static boolean deleteFile(String remoteFilePath, boolean recursive)
throws IOException {
FileSystem fs = FileSystem.get(conf);
boolean result = fs.delete(new Path(remoteFilePath), recursive);
fs.close();
return result;
}
/**
* 删除目录或文件(如果有子目录,则级联删除)
*
* @param remoteFilePath
* @return
* @throws IOException
*/
public static boolean deleteFile(String remoteFilePath) throws IOException {
return deleteFile(remoteFilePath, true);
}
/**
* 文件重命名
*
* @param oldFileName
* @param newFileName
* @return
* @throws IOException
*/
public static boolean renameFile(String oldFileName, String newFileName)
throws IOException {
FileSystem fs = FileSystem.get(conf);
Path oldPath = new Path(oldFileName);
Path newPath = new Path(newFileName);
boolean result = fs.rename(oldPath, newPath);
fs.close();
return result;
}
/**
* 创建目录
*
* @param dirName
* @return
* @throws IOException
*/
public static boolean createDirectory(String dirName) throws IOException {
FileSystem fs = FileSystem.get(conf);
Path dir = new Path(dirName);
boolean result = false;
if (!fs.exists(dir)) {
result = fs.mkdirs(dir);
}
fs.close();
return result;
}
//列出指定路径下的文件
public static RemoteIterator listFiles(String dirPath,boolean recursive) throws IOException {
FileSystem fs = FileSystem.get(conf);
RemoteIterator listFiles = fs.listFiles(new Path(dirPath), recursive);//不进行递归
fs.close();
return listFiles;
}
/**
* 列出指定路径下的文件（非递归）
*
* @param basePath
* @return
* @throws IOException
*/
public static RemoteIterator listFiles(String basePath)
throws IOException {
FileSystem fs = FileSystem.get(conf);
RemoteIterator remoteIterator = fs.listFiles(
new Path(basePath), false);
fs.close();
return remoteIterator;
}
/**
* 列出指定目录下的文件\子目录信息（非递归）
*
* @param dirPath
* @return
* @throws IOException
*/
public static FileStatus[] listStatus(String dirPath) throws IOException {
FileSystem fs = FileSystem.get(conf);
FileStatus[] fileStatuses = fs.listStatus(new Path(dirPath));
fs.close();
return fileStatuses;
}
//读取文件内容
public static byte[] readFile(String filePath) throws IOException {
byte[] fileContent = null;
FileSystem fs = FileSystem.get(conf);
Path path = new Path(filePath);
if (fs.exists(path)){
FSDataInputStream fsin = fs.open(path);
ByteArrayOutputStream bos = new ByteArrayOutputStream();
IOUtils.copyBytes(fsin,bos,conf);
fileContent = bos.toByteArray();
}
return fileContent;
}
//下载hdfs上的文件
public static void download(String remote,String local) throws IOException {
FileSystem fs = FileSystem.get(conf);
//远程hdfs上的文件
Path remotePath = new Path(remote);
//本地的文件
Path localPath = new Path(local);
fs.copyToLocalFile(remotePath,localPath);
fs.close();
}
}