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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#xff0c;存在则读出文件内容#xff0c;打印在控制台上。反之#xff0c;输出“文件不存在”。
package abc;impo…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();}}
}
