JAVA访问HDFS（满满干货！基础操作入门）长夜漫漫，无心睡眠-

下面的入门源码里面都说明了功能，不多说（跑之前别忘了开启Hadoop）

 import java.net.URI;  import org.apache.hadoop.conf.Configuration; import org.apache.hadoop.fs.FSDataInputStream; import org.apache.hadoop.fs.FileSystem; import org.apache.hadoop.fs.Path; import org.apache.hadoop.io.IOUtils;  //读取指定文件，将文件内容输出到控制台 public class ReadData {   public static void main(String[] args) {   // TODO Auto-generated method stub         //定义文件系统路径   String hdfs_address="hdfs://master:9000";   //访问的具体文件路径   String uri=hdfs_address+"/in/words";   //填写配置信息(默认加载core-default.xml和core-site.xml)   Configuration conf=new Configuration();   FSDataInputStream in=null;//输入流字节   try {    //第一个参数必须以对象形式传递，不能是字符串    //第二个参数是配置信息，即上面的Configuration对象    FileSystem fs=FileSystem.get(URI.create(hdfs_address), conf, "czh");    in=fs.open(new Path(uri));       /*第二个参数是输出到控制台，第三个是缓冲区，              第四个是copy完了之后要不要关闭源数据和目的数据        */    //把读到的数据输出到控制台    IOUtils.copyBytes(in, System.out,4096,false);   }catch(Exception e) {    e.printStackTrace();   }   finally {    IOUtils.closeStream(in);//关闭资源   }  }  } 

  import java.net.URI;  import org.apache.hadoop.conf.Configuration; import org.apache.hadoop.fs.FileSystem; import org.apache.hadoop.fs.Path;  //创建目录 public class CreateDir {   public static void main(String[] args) {   // TODO Auto-generated method stub   String hdfs_address="hdfs://master:9000";   Configuration conf=new Configuration();   try {    FileSystem fs=FileSystem.get(URI.create(hdfs_address), conf, "czh");    //mkdirs函数会返回一个布尔值来代表是否创建成功    boolean flag=fs.mkdirs(new Path(hdfs_address+"/my/tmp"));    System.out.println("Directory create"+(flag?"successfully":"failed"));   }catch(Exception e) {    e.printStackTrace();   }   }  } 

  import java.net.URI;  import org.apache.hadoop.conf.Configuration; import org.apache.hadoop.fs.FileSystem; import org.apache.hadoop.fs.Path;  //上传文件 public class PutFile {   public static void main(String[] args) {   // TODO Auto-generated method stub   String hdfs_address="hdfs://master:9000";   try {    FileSystem fs=FileSystem.get(URI.create(hdfs_address), new Configuration(), "czh");       Path src=new Path("D:\a.txt");//注意分割符与Windows下相反,此文件必须存在！       Path dest=new Path(hdfs_address+"/my");//上传目标路径       fs.copyFromLocalFile(src, dest);   }catch(Exception e) {    e.printStackTrace();   }   }  } 

  import java.io.FileOutputStream; import java.net.URI;  import org.apache.hadoop.conf.Configuration; import org.apache.hadoop.fs.FSDataInputStream; import org.apache.hadoop.fs.FileSystem; import org.apache.hadoop.fs.Path; import org.apache.hadoop.io.IOUtils;  //下载文件,并写入到本地D:\my\路径下的b.txt文件中 public class DownFile {   public static void main(String[] args) {   // TODO Auto-generated method stub   String hdfs_address="hdfs://master:9000";   try {    FileSystem fs=FileSystem.get(URI.create(hdfs_address), new Configuration(), "czh");       Path src=new Path(hdfs_address+"/my/a.txt");       FileOutputStream out=new FileOutputStream("D:\my\b.txt");       //open函数用于创建一个输入流，起点是src       FSDataInputStream in=fs.open(src);       IOUtils.copyBytes(in, out, 4096,false); ;  }catch(Exception e) {    e.printStackTrace();   }   }  } 

  import java.net.URI;  import org.apache.hadoop.conf.Configuration; import org.apache.hadoop.fs.FileStatus; import org.apache.hadoop.fs.FileSystem; import org.apache.hadoop.fs.Path;  //列出目录下的文件 public class ListFile {   public static void main(String[] args) {   // TODO Auto-generated method stub   String hdfs_address="hdfs://master:9000";   try {    FileSystem fs=FileSystem.get(URI.create(hdfs_address), new Configuration(), "czh");       FileStatus files[]=fs.listStatus(new Path(hdfs_address+"/my"));       for(FileStatus file:files) {        System.out.println(file.getPath());       } ;  }catch(Exception e) {    e.printStackTrace();   }   }  } 

  import java.net.URI;  import org.apache.hadoop.conf.Configuration; import org.apache.hadoop.fs.FileSystem; import org.apache.hadoop.fs.Path;  //删除文件 public class DeleteFile {   public static void main(String[] args) {   // TODO Auto-generated method stub   String hdfs_address="hdfs://master:9000";   try {    FileSystem fs=FileSystem.get(URI.create(hdfs_address), new Configuration(), "czh");       boolean flag=fs.delete(new Path(hdfs_address+"/my"),true);//第二个参数是是否递归删除       System.out.println("File deleted:"+flag); ;  }catch(Exception e) {    e.printStackTrace();   }   }  }