环境：
virtualbox ubantu1604
Linux idea社区版2023
jdk1.8
hadoop相关依赖
使用java操作
1. 判断/user/stu/input/test.txt文件是否存在，存在则读出文件内容，打印在控制台上。反之，输出“文件不存在”。
package abc;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.IOException;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.fs.FSDataInputStream;
import org.apache.hadoop.fs.FSDataOutputStream;
public class HDFSFlieifExit {
public static void main(String[] args) {
try {
String filename = "input/test.txt";
Configuration conf = new Configuration();
conf.set("fs.defaultFS", "hdfs://localhost:9000");
conf.set("fs.hdfs.impl",
"org.apache.hadoop.hdfs.DistributedFileSystem");
FileSystem fs = FileSystem.get(conf);
Path file = new Path(filename);
if (fs.exists(file)) {
FSDataInputStream getIt = fs.open(file);
BufferedReader d = new BufferedReader(new InputStreamReader(
getIt));
String con = null;
while ((con = d.readLine()) != null) {
System.out.println(con);
}
d.close(); //关闭文件
fs.close(); //关闭hdfs
} else {
System.out.println("文件不存在");
}
} catch (Exception e) {
e.printStackTrace();
}
}
}
2. 使用JAVA编程实现
1） 在根目录下创建hdfsjava目录
package abc;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
public class createDir {
public static void main(String[] args) {
try {
Configuration conf = new Configuration();
conf.set("fs.defaultFS", "hdfs://localhost:9000");
conf.set("fs.hdfs.impl",
"org.apache.hadoop.hdfs.DistributedFileSystem");
FileSystem fs = FileSystem.get(conf);
boolean isok = fs.mkdirs(new Path("hdfs:/hdfsjava"));
if (isok) {
System.out.println("成功创建目录!");
} else {
System.out.println("创建目录失败");
}
fs.close();
} catch (Exception e) {
e.printStackTrace();
}
}
}
2） 在hdfsjava目录下创建文件mobiles.txt，内容是“My telephone is HUAWEI”
package abc;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FSDataOutputStream;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
public class Writemobile {
public static void main(String[] args) {
try {
Configuration conf = new Configuration();
conf.set("fs.defaultFS", "hdfs://localhost:9000");
conf.set("fs.hdfs.impl",
"org.apache.hadoop.hdfs.DistributedFileSystem");
FileSystem fs = FileSystem.get(conf);
Path inFile = new Path("hdfs:/hdfsjava/mobile.txt");
FSDataOutputStream outputStream = fs.create(inFile);
outputStream.writeUTF("My telephone is HUAWEI");
outputStream.flush();
outputStream.close();
fs.close();
} catch (Exception e) {
e.printStackTrace();
}
}
}
3） 将linux本地的myLocalFile.txt文件上传到hdfsjava目录下。
package abc;
import com.sun.org.apache.xerces.internal.util.URI;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FSDataOutputStream;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
public class putfile {
public static void main(String[] args) {
try {
Configuration conf = new Configuration();
conf.set("fs.defaultFS", "hdfs://localhost:9000");
conf.set("fs.hdfs.impl",
"org.apache.hadoop.hdfs.DistributedFileSystem");
FileSystem fs = FileSystem.get(conf);
Path src = new Path("/usr/local/hadoop/myLocalFile.txt");
Path dst = new Path("/hdfsjava");
fs.copyFromLocalFile(src, dst);
System.out.println("上传完成...");
fs.close();
} catch (Exception e) {
e.printStackTrace();
}
}
}
4） 列表显示hdfsjava下的所有文件，打印在控制台上。
package abc;
import com.sun.org.apache.xerces.internal.util.URI;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FSDataOutputStream;
import org.apache.hadoop.fs.FileStatus;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
public class printconsole {
public static void main(String[] args) {
try {
Configuration conf = new Configuration();
conf.set("fs.defaultFS", "hdfs://localhost:9000");
conf.set("fs.hdfs.impl",
"org.apache.hadoop.hdfs.DistributedFileSystem");
FileSystem fs = FileSystem.get(conf);
Path dst = new Path("/hdfsjava");
FileStatus[] status = fs.listStatus(dst);
for (int i = 0; i < status.length; i++) {
System.out.println(status[i].getPath().toString());
}
fs.close();
} catch (Exception e) {
e.printStackTrace();
}
}
}
5） 查看hdfs上的hdfsjava目录下myLocalFile.txt文件内容
package abc;
import com.sun.org.apache.xerces.internal.util.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 java.io.BufferedReader;
import java.io.InputStreamReader;
public class readfile {
public static void main(String[] args) {
try {
Configuration conf = new Configuration();
conf.set("fs.defaultFS", "hdfs://localhost:9000");
conf.set("fs.hdfs.impl",
"org.apache.hadoop.hdfs.DistributedFileSystem");
FileSystem fs = FileSystem.get(conf);
Path dst = new Path("/hdfsjava/myLocalFile.txt");
FSDataInputStream in = fs.open(dst);
BufferedReader d = new BufferedReader(new InputStreamReader(in));
String line = null;
while ((line = d.readLine()) != null) {
String[] stra = line.split(" ");
for (int i = 0; i < stra.length; i++) {
System.out.print(stra[i]);
System.out.print(" ");
}
System.out.println(" ");
}
fs.close();
} catch (Exception e) {
e.printStackTrace();
}
}
}
6） 将hdfs上的hdfsjava目录下mobiles.txt文件下载到本地/home/hadoop中。
7） 删除hdfsjava目录。
package abc;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
public class delete {
public static void main(String[] args) {
try {
Configuration conf = new Configuration();
conf.set("fs.defaultFS", "hdfs://localhost:9000");
conf.set("fs.hdfs.impl",
"org.apache.hadoop.hdfs.DistributedFileSystem");
FileSystem fs = FileSystem.get(conf);
Path src = new Path("/hdfsjava");
fs.delete(src, true);
} catch (Exception e) {
e.printStackTrace();
}
}
}
