java客户端运行hadoop_【Hadoop教程】（七）HDFS JAVA客户端操作

hdfs在生产应用中主要是客户端的开发，其核心步骤是从hdfs提供的api中构造一个HDFS的访问客户端对象，然后通过该客户端对象操作HDFS上的文件(如增删改查)。案例如下：

package lyl.hadoop;

import org.apache.hadoop.conf.Configuration;

import org.apache.hadoop.fs.*;

import org.apache.hadoop.io.IOUtils;

import java.io.File;

import java.io.FileInputStream;

import java.io.IOException;

public class HadoopFileSystem {

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

read();

}

/**

* 从HDFS上读取文件输出到控制台

* @throws IOException

*/

public static void read() throws IOException {

Configuration configuration = new Configuration();

FileSystem fileSystem = FileSystem.get(configuration);

Path path = new Path("/user/flume/hiveLogs/FlumeData.1517279361739");

FSDataInputStream inputStream = fileSystem.open(path);

IOUtils.copyBytes(inputStream, System.out, 4094);

IOUtils.closeStream(inputStream);

}

/**

* 将本地文件写入到HDFS

* @throws IOException

*/

public static void write() throws IOException {

Configuration configuration = new Configuration();

FileSystem fileSystem = FileSystem.get(configuration);

Path path = new Path("/user/write.txt");

FSDataOutputStream fsDataOutputStream = fileSystem.create(path);

FileInputStream fileInputStream = new FileInputStream(new File("D:\\README.txt"));

IOUtils.copyBytes(fileInputStream, fsDataOutputStream, 4094);

IOUtils.closeStream(fileInputStream);

}

/**

* 删除HDFS文件

* @throws IOException

*/

public static void delete() throws IOException {

Configuration configuration = new Configuration();

FileSystem fileSystem = FileSystem.get(configuration);

Path path = new Path("/user/README.txt");

fileSystem.delete(path, true);

}

/**

* 创建目录

* @throws IOException

*/

public static void mkdir() throws IOException {

Configuration configuration = new Configuration();

FileSystem fileSystem = FileSystem.get(configuration);

Path path = new Path("/lyl");

fileSystem.mkdirs(path);

}

/**

* 获取文件或者目录具体信息 如blocksize replication owner permission

* @throws IOException

*/

public static void getFileStatus() throws IOException {

Configuration configuration = new Configuration();

FileSystem fileSystem = FileSystem.get(configuration);

Path path = new Path("/user");

FileStatus fileStatus = fileSystem.getFileStatus(path);

System.out.println(fileStatus);

}

/**

* 获取该目录下所有文件的具体信息

* @throws IOException

*/

public static void ListFileSatuts() throws IOException {

Configuration configuration = new Configuration();

FileSystem fileSystem = FileSystem.get(configuration);

Path path = new Path("/user");

FileStatus[] fileStatus = fileSystem.listStatus(path);

for (FileStatus fileStatus1 : fileStatus) {

System.out.println(fileStatus1);

}

}

}

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