主要操作HDFS文件的查看，添加，删除，上传，下载。完整源码见后面
环境搭建见：https://blog.csdn.net/qq_25948717/article/details/82015131
Maven就是方便包的管理版本匹配
搭建好如图：
配置：
可以看到右下角正在下载依赖，第一耗时很长
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开发：将所有操作都作为单元测试，先删除test下的AppTest，新建包和java测试类
创建文件：
package com.yexin.hadoop.hdfs;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;
import java.net.URI;
/**
* @Company: Huazhong University of science and technology
* @version: V1.0
* @author: YEXIN
* @contact: [email protected] or [email protected] 2018--2020
* @software: IntelliJ IDEA
* @file: HDFSApp
* @time: 8/24/18 2:11 PM
* @Desc:Hadoop HDFS Java API Operation
**/
public class HDFSApp {
public static final String HDFS_PATH = "hdfs://node40:9000";
FileSystem fileSystem = null;//important class for operating the hdfs file
Configuration configuration = null;
/**
*mkdir HDFS file
* */
@Test
public void mkdir() throws Exception{
fileSystem.mkdirs(new Path("/hdfsapi/test"));
}
//prepare the environment before execute the junit test
@Before
public void setUp() throws Exception{
System.out.println("HDFSApp.setUp");
configuration = new Configuration();
fileSystem = FileSystem.get(new URI(HDFS_PATH),configuration,"test");
}
//release resource of app
@After
public void tearDown() throws Exception{
configuration = null;
fileSystem = null;
System.out.println("HDFSApp.tearDown");
}
}
鼠标选择mkdir()方法，右键选择运行mkdir()，
在控制台输入查看可以看到创建成功：
网页查看：
创建文件并且写入内容：同样的方式运行
在终端测查看：
重命名：
结果：
从本地传输文件到HDFS：
结果：
输出目录下的所有文件：
结果：
结果解读：
完整源码：
package com.yexin.hadoop.hdfs;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.*;
import org.apache.hadoop.io.IOUtils;
import org.apache.hadoop.util.Progressable;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;
import sun.nio.ch.IOUtil;
import java.io.BufferedInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.InputStream;
import java.net.URI;
/**
* Company: Huazhong University of science and technology
* version: V1.0
* author: YEXIN
* contact: [email protected] or [email protected] 2018--2020
* software: IntelliJ IDEA
* file: HDFSApp
* time: 8/24/18 2:11 PM
* Desc:Hadoop HDFS Java API Operation
**/
public class HDFSApp {
public static final String HDFS_PATH = "hdfs://node40:9000";
FileSystem fileSystem = null;//important class for operating the hdfs file
Configuration configuration = null;
/**
*mkdir HDFS file
* */
@Test
public void mkdir() throws Exception{
fileSystem.mkdirs(new Path("/hdfsapi/test"));
}
/**
* create file
* @throws Exception
*/
@Test
public void createFile() throws Exception{
FSDataOutputStream output = fileSystem.create(new Path("/hdfsapi/test/test.txt"));//fileSystem.create() returns a data stream,
// so we will get the steam,and use it to write some contents.
output.writeBytes("hadoop-hello");
//flush and close
output.flush();
output.close();
}
/**
* cat file contents
* @throws Exception
*/
@Test
public void cat() throws Exception{
FSDataInputStream input = fileSystem.open(new Path("/hdfsapi/test/test.txt"));
//output to console
IOUtils.copyBytes(input,System.out,1024);
input.close();
}
/**
* rename file's name
* @throws Exception
*/
@Test
public void rename() throws Exception{
Path oldPath = new Path("/hdfsapi/test/test.txt");
Path newPath = new Path("/hdfsapi/test/testnew.txt");
fileSystem.rename(oldPath,newPath);
}
/**
* copy local file to HDFS
* @throws Exception
*/
@Test
public void copyFromLocalFile() throws Exception{
//be careful:localpath is your development platform ,not node40,it's node100
Path localPath = new Path("/public/users/test/Packages/jdk-8u172-linux-x64.tar.gz");
Path hdfsPath = new Path("/hdfsapi/test");
fileSystem.copyFromLocalFile(localPath,hdfsPath);
}
/**
* cpoy local file to hdfs with Progress
* @throws Exception
*/
@Test
public void copyFromLocalFilewithProgress() throws Exception{
//be careful:localpath is your development platform ,not node40,it's node100
Path localPath = new Path("/public/users/test/Packages/jdk-8u172-linux-x64.tar.gz");
Path hdfsPath = new Path("/hdfsapi/test");
fileSystem.copyFromLocalFile(localPath,hdfsPath);
InputStream input = new BufferedInputStream(
new FileInputStream(
new File("/public/users/test/Packages/jdk-8u172-linux-x64.tar.gz")));
FSDataOutputStream output = fileSystem.create(new Path("/hdfsapi/test/jdk.tar.gz"),
new Progressable() {
public void progress() {
System.out.println("===");//show Progress
}
});
IOUtils.copyBytes(input,output,1024);
}
/**
* download hdfs file to local
* @throws Exception
*/
@Test
public void copyToLocal() throws Exception{
Path localPath = new Path("/public/users/test/Packages");
Path hdfspath = new Path("/hdfsapi/test/jdk.tar.gz");
fileSystem.copyToLocalFile(hdfspath,localPath);
}
/**
* cat the directory's all files
* @throws Exception
*/
@Test
public void listFiles() throws Exception{
FileStatus[] fileStatuses = fileSystem.listStatus(new Path("/hdfsapi/test"));//the method returns a array
for(FileStatus fileStatu:fileStatuses){
String isDir = fileStatu.isDirectory() ? "Dir":"File";
short replication = fileStatu.getReplication();
long size = fileStatu.getLen();
String path = fileStatu.getPath().toString();
System.out.println(isDir+"\t"+replication+"\t"+size+"\t"+path);
}
}
/**
* delete file
* @throws Exception
*/
@Test
public void delete() throws Exception{
fileSystem.delete(new Path("/hdfsapi/test/jdk.tar.gz"),true);
}
//prepare the environment before execute the junit test
@Before
public void setUp() throws Exception{
System.out.println("HDFSApp.setUp");
configuration = new Configuration();
fileSystem = FileSystem.get(new URI(HDFS_PATH),configuration,"test");
}
//release resource of app
@After
public void tearDown() throws Exception{
configuration = null;
fileSystem = null;
System.out.println("HDFSApp.tearDown");
}
}