HDFS client 实例

package hdfs;


import java.io.IOException;
import java.net.URI;
import java.net.URISyntaxException;

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 HdfsBuildData
    //initialization
    static Configuration conf = new Configuration();
    static FileSystem hdfs;
    public static final  String HADOOP_PATH="hdfs://127.0.0.1:9000";
    static {
        try {
            hdfs=FileSystem.get(new URI(HADOOP_PATH),new Configuration());
        } catch (IOException e) {
            e.printStackTrace();
        } catch (URISyntaxException e) {
            e.printStackTrace();
        }
    }

    //create a direction
    public void createDir(String dir) throws IOException {
        Path path = new Path(dir);
        hdfs.mkdirs(path);
        System.out.println("new dir \t" + conf.get("fs.default.name") + dir);
    }   

    //copy from local file to HDFS file
    public void copyFile(String localSrc, String hdfsDst) throws IOException{
        Path src = new Path(localSrc);      
        Path dst = new Path(hdfsDst);
        hdfs.copyFromLocalFile(src, dst);

        //list all the files in the current direction
        FileStatus files[] = hdfs.listStatus(dst);
        System.out.println("Upload to \t" + conf.get("fs.default.name") + hdfsDst);
        for (FileStatus file : files) {
            System.out.println(file.getPath());
        }
    }

    //create a new file
    public void createFile(String fileName, String fileContent) throws IOException {
        Path dst = new Path(fileName);
        byte[] bytes = fileContent.getBytes();
        FSDataOutputStream output = hdfs.create(dst);
        output.write(bytes);
        output.close();
        System.out.println("new file \t" + conf.get("fs.default.name") + fileName);
    }

    //list all files
    public void listFiles(String dirName) throws IOException {
        Path f = new Path(dirName);
        FileStatus[] status = hdfs.listStatus(f);
        System.out.println(dirName + " has all files:");
        for (int i = 0; i< status.length; i++) {
            System.out.println(status[i].getPath().toString());
        }
    }

    //judge a file existed? and delete it!
    public void deleteFile(String fileName) throws IOException {
        Path f = new Path(fileName);
        boolean isExists = hdfs.exists(f);
        if (isExists) { //if exists, delete
            boolean isDel = hdfs.delete(f,true);
            System.out.println(fileName + "  delete? \t" + isDel);
        } else {
            System.out.println(fileName + "  exist? \t" + isExists);
        }
    }

    public static void main(String[] args) throws IOException {
        HdfsBuildData ofs = new HdfsBuildData();
        System.out.println("\n=======create dir=======");
        String dir = "/test";
        ofs.createDir(dir);
        System.out.println("\n=======create a file=======");
        String fileContent = "Hello, world! Just a test.";
        ofs.createFile(dir+"/word.txt", fileContent);
    }
}