Hadoop Java API 读写文件系统

package com.zt.hdfs;

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

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 org.apache.hadoop.hdfs.DistributedFileSystem;
import org.apache.hadoop.io.IOUtils;

public class Hdfs {
private static Configuration configuration;
private static URI uri;
private static FileSystem fileSystem;
private static FileSystem localSystem;

public static void main(String [] args) throws IOException, URISyntaxException{

    init();
    getFileStatus("/data/a.txt");
    deleteFileOrDir("/data/a.txt",true);
    mkdir("/data");
    createFile("/data/b.txt");
    getFileStatusFromDir("/data");
    writeFile("/data/b.txt");
    readFile("/data/b.txt");
    deleteFileOrDir("/test", true);
    mergeFile("/home/hadoop/test/", "/test/merge.txt");
}


/*
 * initialize the Haddop Cluster configuration
 */
public static void init() throws URISyntaxException, IOException{
    configuration = new Configuration();
    URI uri = new URI("hdfs://Master:9000");
    fileSystem = (DistributedFileSystem) FileSystem.get(uri, configuration);
    localSystem = FileSystem.getLocal(configuration);

}


/*
 * create File 
 * 
 */

public static void createFile(String fileName) throws IllegalArgumentException, IOException{
    FSDataOutputStream outputStream = fileSystem.create(new Path(fileName));

}

public static void readFile(String fileName) throws IllegalArgumentException, IOException{
    FSDataInputStream inputStream = fileSystem.open(new Path(fileName));
    IOUtils.copyBytes(inputStream, System.out, configuration);
    IOUtils.closeStream(inputStream);
}

public static void writeFile(String fileName) throws IllegalArgumentException, IOException{
    FSDataOutputStream fsDataOutputStream = fileSystem.create(new Path(fileName));
    byte[] bytes = "hello, hadoop".getBytes();
    fsDataOutputStream.write(bytes, 0, bytes.length);
    fsDataOutputStream.close();
}

/*
 * create a directory
 */
public static void mkdir(String dirName) throws IOException{
    Path dir = new Path(dirName);
    boolean flag = fileSystem.mkdirs(dir);
    if (flag) {
        System.out.println("success to mkdir " + dirName);
    }else {
        System.out.println("fialed to mkdir " + dirName);
    }

}



/*
 * delete a file or directory 
 */
public static void deleteFileOrDir(String dirName,boolean recursive) throws IllegalArgumentException, IOException {
    boolean flag = fileSystem.delete(new Path(dirName), recursive);
    System.out.println("flag=" + flag);

}

/*
 * list a detail information about a file
 */
public static void getFileStatus(String filePath) throws IOException {
    Path path = new Path(filePath);
    FileStatus fileStatus = fileSystem.getFileStatus(path);
    System.out.println(fileStatus);
    System.out.println("path= " +fileStatus.getPath() );
    System.out.println("IsDirectory=" + fileStatus.isDirectory());
    System.out.println("length:" + fileStatus.getLen());
    System.out.println("replication=" + fileStatus.getReplication());
    System.out.println("owner:" + fileStatus.getOwner());
    System.out.println("group:" + fileStatus.getGroup());
    System.out.println("Permission:" + fileStatus.getPermission());
    System.out.println("isSymlink:" + fileStatus.isSymlink());
    System.out.println("blockSize=" + fileStatus.getBlockSize() / 1024 / 1024 + "M");

}

/*
 * get all files detail information  in a directory
 */
public static void getFileStatusFromDir(String dirName) throws FileNotFoundException, IllegalArgumentException, IOException{
    FileStatus[] listStatus = fileSystem.listStatus(new Path(dirName));
    for (FileStatus fileStatus : listStatus) {
        System.out.println(fileStatus);
    }

}

/*
 * merge file from local file system to Hdfs
 */
public static void mergeFile(String dirName,String hdfsFileName) throws FileNotFoundException, IllegalArgumentException, IOException{

    FileStatus[] listStatus = localSystem.listStatus(new Path(dirName));
    Path hdfsfile = new Path(hdfsFileName);
    FSDataOutputStream fsDataOutputStream = fileSystem.create(new Path(hdfsFileName));
    for (FileStatus fileStatus : listStatus) {
        Path path = fileStatus.getPath();
        FSDataInputStream fsDataInputStream = localSystem.open(path);
        byte[] buffer = new byte[256];
        int len ;
        while((len = fsDataInputStream.read(buffer)) > 0){
            fsDataOutputStream.write(buffer, 0, len);
        }
        fsDataInputStream.close();
    }
    fsDataOutputStream.close();


}

}