Hadoop 编程实战：HDFS API 编程样例

package cdh_dev_demo;
import org.apache.hadoop.conf.Configuration;import org.apache.hadoop.fs.*;import org.apache.hadoop.fs.permission.FsPermission;import org.apache.hadoop.io.IOUtils;
import java.io.BufferedReader;import java.io.IOException;import java.io.InputStreamReader;import java.text.SimpleDateFormat;import java.util.Date;
public class HdfsMethodDemo {    public static void main(String args[]) throws IOException {        HdfsMethodDemo h=new HdfsMethodDemo();        FileSystem fs = getfs();        //执行方法        fs.close();    }
    //创建HDFS Configuration配置项    private static Configuration getconf(){        Configuration conf = new Configuration();        conf.set("fs.defaultFS","hdfs://namenode.cdh.com:8020");        return conf;    }
    //创建HDFS文件对象    private static FileSystem getfs() throws IOException{        Configuration conf = getconf();        FileSystem fs = FileSystem.get(conf);        return fs;    }
    //拷贝本地文件到HDFS    public static void CopyLocalToHdfs(FileSystem fs,String LocalPath,String HdfsPath) throws IOException{        Path local = new Path(LocalPath);        Path hdfs = new Path(HdfsPath);        fs.copyFromLocalFile(local,hdfs);        //查看文件是否复制成功        FileStatus files[] = fs.listStatus(hdfs);        for (FileStatus file:files){            System.out.println(file.getPath().toString());        }    }
    //拷贝HDFS文件到本地    public static void CopyHdfsToLocal(FileSystem fs,String LocalPath,String HdfsPath) throws IOException {        Path local = new Path(LocalPath);        Path hdfs = new Path(HdfsPath);        fs.copyToLocalFile(false,hdfs,local,true);    }
    //创建HDFS目录    public static void MkdirHdfsPath(FileSystem fs,String HdfsPath) throws IOException{        fs.mkdirs(new Path(HdfsPath));    }
    //HDFS系统内文件拷贝    public static void CopyHdfsToHdfs(FileSystem fs,String SrcHdfsPath,String TargetHdfsPath) throws IOException{        FSDataInputStream fsin = fs.open(new Path(SrcHdfsPath));        FSDataOutputStream fsout = fs.create(new Path(TargetHdfsPath));        IOUtils.copyBytes(fsin,fsout,1024,true);    }
    //创建HDFS文件    public static void CreateHdfsFile(FileSystem fs,String HdfsPath) throws IOException{        fs.create(new Path(HdfsPath));    }
    //查看HDFS文件元信息    public static void SelHdfsMetadata(FileSystem fs,String HdfsPath) throws IOException{        FileStatus[] stat = fs.listStatus(new Path(HdfsPath));        for (FileStatus f:stat) {            long accessTime = f.getAccessTime();    //创建时间            SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");            long blockSize = f.getBlockSize();      //块大小            String group = f.getGroup();            //用户组            long len = f.getLen();                  //文件长度            long modificationTime = f.getModificationTime();            //修改时间            String owner = f.getOwner();            //用户            Path path = f.getPath();                //路径            FsPermission permission = f.getPermission();    //权限            short replication = f.getReplication();         //副本数            String string = f.toString();                   //f集合所有内容            boolean directory = f.isDirectory();            //判断是否目录            boolean encrypted = f.isEncrypted();            //判断是否加密            boolean file = f.isFile();                      //判断是否文件
            System.out.println("AccessTime:"+sdf.format(new Date(accessTime)));            System.out.println("BlockSize:"+blockSize);            System.out.println("Group:"+group);            System.out.println("Length:"+len);            System.out.println("ModificationTime:"+sdf.format(new Date(modificationTime)));            System.out.println("Owner:"+owner);            System.out.println("Path:"+path);            System.out.println("Permission:"+permission);            System.out.println("Replication:"+replication);            System.out.println("StatusList:"+string);            System.out.println("IsDirectory:"+directory);            System.out.println("IsEncrypted:"+encrypted);            System.out.println("IsFile:"+file);            System.out.println("\n");        }    }
    //删除HDFS文件    public static void DeleteHdfsFile(FileSystem fs,String HdfsPath) throws IOException{        FileStatus[] stat = fs.listStatus(new Path(HdfsPath));        for (FileStatus f:stat) {            System.out.println("IsFile?"+f.isFile());            System.out.println("IsDirectory?"+f.isDirectory());            if (f.isFile() == true)                //删除文件                fs.delete(new Path(f.getPath().toString()),false);            else if (f.isDirectory() == true)                //删除目录及目录下所有文件                fs.delete(new Path(f.getPath().toString()),true);        }    }
    //把HDFS文件内容逐行读取并输出到屏幕    public static void ReadHdfsFile(FileSystem fs,String HdfsPath) throws IOException{        FSDataInputStream fin = fs.open(new Path(HdfsPath));        int i=0; //行数        String s=null;        BufferedReader br = new BufferedReader(new InputStreamReader(fin));        while (((s = br.readLine()) != null)){            i++;            System.out.println("第"+i+"行："+s);        }    }
    //把1-10数字逐行写入到HDFS文件    public static void WriteHdfsFile(FileSystem fs,String HdfsPath) throws IOException{        //若文件存在，则进行删除        if (fs.exists(new Path(HdfsPath)))            DeleteHdfsFile(fs,HdfsPath);        FSDataOutputStream fout = fs.create(new Path(HdfsPath));        for (int i=0;i<=10;i++){            byte[] buffer = (i+"\n").getBytes();            fout.write(buffer);        }    }}