eclipse通过hdfs提供的api对hdfs进行文件操作

上一文介绍了在本机windows搭建一个伪分布式环境，接下来就是在eclipse进行hdfs文件的读写等操作。

第一步需要获取eclipse进行hadoop开发的插件支持，hadoop第一代和第二代不同，第二代貌似没直接给插件，需要网上找，第一代的有，怎样去获取呢？想必大家很关心，我开始也纳闷这玩意儿在哪里？在网上也找过放进去结果没用，不知道是什么问题。后来查资料发现第一代的安装包有给。

拿到jar包找到eclipse的安装目录下的plugins文件夹下面，然后重启eclipse，接下来打开就发现有个蓝色大象，你可以在eclipse直接看hdfs上面的文件，点击新建一个连接

接下来写代码进行操作

package com.qqw.hadoop;

import java.io.BufferedOutputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.net.URI;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.BlockLocation;
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;


public class HdfsUtil {

	private  Configuration conf = new Configuration();
    private FileSystem coreSys=null;
	private String rootPath=new String("hdfs://localhost:9000/");
	 /**
     * 在HDFS上创建文件目录     
	 * @throws IOException */

    public void createDirOnHDFS() throws IOException{
    	
       coreSys=FileSystem.get(URI.create(rootPath), conf);	
       Path demoDir=new Path(rootPath+"demoDir");
       boolean isSuccess=true;
        try {
           isSuccess=coreSys.mkdirs(demoDir);
        } catch (IOException e) {
           isSuccess=false;
      }
      System.out.println(isSuccess?"目录创建成功！":"目录创建失败!");
          
    }
    
    /**
     * 在hdfs上创建文件
     * @throws IOException 
     */
    public void createFileOnHDFS() throws IOException{
    	
    	 coreSys=FileSystem.get(URI.create(rootPath), conf);
         Path hdfsPath = new Path(rootPath + "demoDir/createDemoFile1.txt");
		 System.out.println(coreSys.getHomeDirectory());
		 String content = "Hello hadoop,this is first time that I create file on hdfs";
		 FSDataOutputStream fsout = coreSys.create(hdfsPath);
		 BufferedOutputStream bout = new BufferedOutputStream(fsout);
		 bout.write(content.getBytes(), 0, content.getBytes().length);
         bout.close();
         fsout.close();
		 System.out.println("文件创建完毕！");
    }
    
    
    /**
     * 从hdfs上下载文件到本地
     * @throws IOException 
     */
    public void downLoadFromHdfs() throws IOException{
    	  coreSys=FileSystem.get(URI.create(rootPath), conf);
    	  Path hdfsPath = new Path(rootPath + "demoDir/createDemoFile1.txt");   
    	  FSDataInputStream hdfsInStream = coreSys.open(hdfsPath); 	  
    	  OutputStream out = new FileOutputStream("D:\\createDemoFile1.txt");
    	  byte[] ioBuffer = new byte[1024];
    	  int readLen = hdfsInStream.read(ioBuffer);
    	  while(-1 != readLen){
	    	  out.write(ioBuffer, 0, readLen);  
	    	  readLen = hdfsInStream.read(ioBuffer);
    	  }
    	  out.close();
    	  hdfsInStream.close();
    	  coreSys.close();
    }
    
    /**
     * 上传文件到hdfs
     * @throws IOException 
     */
    public void upLoadFromHdfs() throws IOException{
    	
    	coreSys=FileSystem.get(URI.create(rootPath), conf);
    	Path remotePath=new Path(rootPath+"demoDir/");
    	coreSys.copyFromLocalFile(new Path("D:\\qq.txt"), remotePath);
    	System.out.println("Upload to:"+conf.get("fs.default.name"));
    	FileStatus [] files=coreSys.listStatus(remotePath);
    	for(FileStatus file:files){
    	     System.out.println(file.getPath().toString());
    	}
    }
    
    
    /**
     * 重命名文件
     * @throws IOException 
     */
    public void rename() throws IOException{
    	
    	coreSys=FileSystem.get(URI.create(rootPath), conf);
    	 Path oldFileName=new Path(rootPath+"demoDir/createDemoFile1.txt");
		 Path newFileName=new Path(rootPath+"demoDir/newDemoFile.txt");
		 boolean isSuccess=true;
		 try {
		    isSuccess=coreSys.rename(oldFileName, newFileName);
		 } catch (IOException e) {
		    isSuccess=false;
		         }
		 System.out.println(isSuccess?"重命名成功！":"重命名失败！");
    }
    
    /**
     * 删除文件
     * @throws IOException 
     */
    public void deleteFile() throws IOException{
    	
    	coreSys=FileSystem.get(URI.create(rootPath), conf);
    	Path deleteFile=new Path(rootPath+"demoDir/qq.txt");
        boolean isSuccess=true;
        try {
		
        	isSuccess=coreSys.delete(deleteFile, false);
		} catch (IOException e) {
		
			isSuccess=false;
	    }
		System.out.println(isSuccess?"删除成功!":"删除失败！");
    }
    
    /**
     * 查看文件是否存在
     * @throws IOException 
     */
    public void exitFile() throws IOException{
    	
    	coreSys=FileSystem.get(URI.create(rootPath), conf);
    	Path checkFile=new Path(rootPath+"demoDir/qq.txt");
        boolean isSuccess=true;
        try {
		
        	isSuccess=coreSys.exists(checkFile);
		} catch (IOException e) {
		
			isSuccess=false;
	    }
		System.out.println(isSuccess?"存在!":"不存在！");
    }
    
    /**
     * 获取某个路径下的全部文件
     * @throws IOException 
     */
    public void allFile() throws IOException{
    	
    	coreSys=FileSystem.get(URI.create(rootPath), conf);
    	Path targetDir=new Path(rootPath+"demoDir/");
    	FileStatus [] files=coreSys.listStatus(targetDir);
    	for(FileStatus file:files){
   	     
    		System.out.println(file.getPath()+"--"+file.getGroup()+"--"+file.getBlockSize()
    		+"--"+file.getLen()+"--"+file.getModificationTime()+"--"+file.getOwner());
   	    }
    }
    
    /** *
     *  查看某个文件在HDFS集群的位置
     * @throws IOException 
     */
	 public void findLocationOnHadoop() throws IOException{
		 
		coreSys=FileSystem.get(URI.create(rootPath), conf); 
		Path targetFile=new Path(rootPath+"demoDir/qq.txt");
		FileStatus fileStaus=coreSys.getFileStatus(targetFile);
		BlockLocation []bloLocations=coreSys.getFileBlockLocations(fileStaus, 0, fileStaus.getLen());
		for(int i=0;i"+dataInfos[j].getDatanodeReport()+"-->"+ 
			 dataInfos[j].getDfsUsedPercent()+"-->"+dataInfos[j].getLevel());
		 }
	     
	 }
    
}

然后可以写个main方法或junit测试，用hadoop跑，可以在eclipse上或访问网页http://localhost:50070实时参看hdfs上文件。