Java程序调用Hadoop接口入门_java使用hadoop

作者：一键难忘520 | 2024-06-20 17:07:11

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java使用hadoop

一、安装Hadoop集群环境

参考http://blog.itpub.net/29485627/viewspace-2137702/

二、程序编写

1 整个程序的目录为

2 HdfsUtil.java中的代码为


package hadoop.hdfs;
 
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.Arrays;
import java.util.List;
 
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.hdfs.protocol.DatanodeInfo;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
 
/**
 * @author 作者 : yangyang
 * @version 创建时间：2016年4月21日 类说明 ：hdfs文件系统操作类
 */
public class HdfsUtil {
 
	private static final Logger log = LoggerFactory.getLogger(HdfsUtil.class);
	// 初始化
	static Configuration conf = new Configuration();
	static FileSystem hdfs;
	static {
		try {
			hdfs = FileSystem.get(conf);
		} catch (IOException e) {
			if (log.isDebugEnabled())
				log.debug("初始化hadoop配置失败", e);
		}
	}
 
	/**
	 * 创建文件夹
	 * 
	 * @param dir
	 * @throws IOException
	 */
	public static boolean mkDirs(String dir) {
		try {
			Path path = new Path(dir);
			return hdfs.mkdirs(path);
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		return false;
	}
 
	/**
	 * 本地文件上传到hdfs
	 * 
	 * @param localSrc
	 * @param hdfsDst
	 * @throws IOException
	 */
	public static void uploadFile(String localSrc, String hdfsDst) throws IOException {
		Path src = new Path(localSrc);
		Path dst = new Path(hdfsDst);
		hdfs.copyFromLocalFile(src, dst);
 
		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());
		}
	}
	
	/**
	 * 下载文件到本地
	 * @param remotePath hdfs文件目录
	 * @param localPath 本地文件目录
	 */
	public static void downLoadFile(String remotePath, String localPath) {
 
		Path _remotePath = new Path(remotePath);
		Path _localPath = new Path(localPath);
		
		try {
			hdfs.copyToLocalFile(false,_remotePath, _localPath,true);
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} finally {
 
			try {
				hdfs.close();
			} catch (IOException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
 
		}
 
	}
 
	/**
	 * 创建文件
	 * 
	 * @param fileName
	 * @param fileContent
	 * @throws IOException
	 */
	public static void createFile(String fileName, String fileContent) {
		Path dst = new Path(fileName);
		byte[] bytes = fileContent.getBytes();
		FSDataOutputStream output;
		
		try {
			output = hdfs.create(dst);
			output.write(bytes);
		} catch (IOException e) {
			if (log.isDebugEnabled())
				log.debug("创建文件异常:" + fileName, e);
		}
		System.out.println("new file \t" + conf.get("fs.default.name")
				+ fileName);
	}
	
	/**
	 * 获取文件内容
	 * @param fileName 文件名
	 * @return
	 */
	public static String readFileContent(String fileName){
		Path p = new Path(conf.get("fs.default.name")+fileName);
		FSDataInputStream in = null;
		String content = "";
		
		try {
			in = hdfs.open(p);
			BufferedReader buff = new BufferedReader(new InputStreamReader(in));
			content = buff.readLine();
			buff.close();
			in.close();
			hdfs.close();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			if(log.isDebugEnabled())
				log.debug("读取文件:"+fileName+"失败", e);
		}
		
		return content;
	}
 
	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());
		}
	}
 
	/**
	 * 删除文件
	 * 
	 * @param fileName
	 *            文件路径
	 * @throws IOException
	 */
	public static boolean deleteFile(String fileName) throws IOException {
		Path f = new Path(fileName);
		boolean isExists = hdfs.exists(f);
		if (isExists) {
			boolean isDel = hdfs.delete(f, true);
			return isDel;
		} else {
			return false;
		}
	}
 
	/**
	 * 获取集群上的所有节点名称
	 * 
	 * @throws IOException
	 */
	public static List<DatanodeInfo> getDateNodeHost() throws IOException {
		DistributedFileSystem _hdfs = (DistributedFileSystem) hdfs;
		DatanodeInfo[] dataNodeStats = _hdfs.getDataNodeStats();
		List<DatanodeInfo> dataNodeLst = Arrays.asList(dataNodeStats);
		return dataNodeLst;
	}
 
	/**
	 * 文件重命名
	 * 
	 * @param fileName
	 *            文件名
	 * @param newFileName
	 *            新文件名
	 * @throws IOException
	 */
	public static boolean renameFile(String fileName, String newFileName) {
 
		Path path = new Path(fileName);
		Path newPath = new Path(newFileName);
		boolean b = false;
		try {
			b = hdfs.rename(path, newPath);
		} catch (Exception e) {
			if (log.isDebugEnabled())
				log.debug("文件:[" + fileName + "]修改为:[" + newFileName + "]失败", e);
		}
		return b;
	}
 
	public static void main(String[] args) throws IOException {
/*		System.err.println(mkDirs("/test"));
		createFile("/test/my.txt", "I Love Beijing!");
		System.out.println(readFileContent("/test/my.txt"));*/
//		deleteFile("/test/my.txt");
//		uploadFile("F:\\a1.txt", "/test");
		downLoadFile("/test/a1.txt", "F:\\a2.txt");
	}
}