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Hadoop HDFS文件操作的Java代码

时间：2014-03-23 09:42:36   收藏：0   阅读：511

1、创建目录

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import java.io.IOException;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
 
public class MakeDir {
    public static void main(String[] args) throws IOException {
        Configuration conf = new Configuration();
        FileSystem fs = FileSystem.get(conf);
        Path path = new Path("/user/hadoop/hdfs/xxxx");
        fs.create(path);
        fs.close();
    }
}

2、删除目录

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import java.io.IOException;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
 
public class DeleteDir {
    public static void main(String[] args) throws IOException {
        Configuration conf = new Configuration();
        FileSystem fs = FileSystem.get(conf);
         
        Path path = new Path("/user/hadoop/hdfs/xxxx");
        fs.delete(path);
        fs.close();
    }
}

3、写文件

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import java.io.IOException;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FSDataOutputStream;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
 
public class WriteFile {
    public static void main(String[] args) throws IOException {
        Configuration conf = new Configuration();
        FileSystem fs = FileSystem.get(conf);
        Path path = new Path("/user/hadoop/hdfs/xxxx.txt");
        FSDataOutputStream out = fs.create(path);
        out.writeUTF("da jia hao,cai shi zhen de hao!");
        fs.close();
    }
}

4、读文件

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import java.io.IOException;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FSDataInputStream;
import org.apache.hadoop.fs.FileStatus;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
 
public class ReadFile {
    public static void main(String[] args) throws IOException {
        Configuration conf = new Configuration();
        FileSystem fs = FileSystem.get(conf);
        Path path = new Path("/user/hadoop/hdfs/xxxx.txt");
         
        if(fs.exists(path)){
            FSDataInputStream is = fs.open(path);
            FileStatus status = fs.getFileStatus(path);
            byte[] buffer = new byte[Integer.parseInt(String.valueOf(status.getLen()))];
            is.readFully(0, buffer);
            is.close();
            fs.close();
            System.out.println(buffer.toString());
        }
    }
}

5、上传本地文件到HDFS

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import java.io.IOException;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
 
public class CopyFromLocalFile {
 
    public static void main(String[] args) throws IOException {
         
        Configuration conf = new Configuration();
        FileSystem fs = FileSystem.get(conf);
        Path src = new Path("/home/hadoop/xxxx.txt");
        Path dst = new Path("/user/hadoop/hdfs/");
        fs.copyFromLocalFile(src, dst);
        fs.close();
    }
}

6、删除文件

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import java.io.IOException;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
 
public class DeleteFile {
 
    public static void main(String[] args) throws IOException {
        Configuration conf = new Configuration();
        FileSystem fs = FileSystem.get(conf);
         
        Path path = new Path("/user/hadoop/hdfs/xxxx.txt");
        fs.delete(path);
        fs.close();
    }
}

7、获取给定目录下的所有子目录以及子文件

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import java.io.IOException;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileStatus;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
 
public class GetAllChildFile {
    static Configuration conf = new Configuration();
     
     
    public static void main(String[] args)throws IOException {
        FileSystem fs = FileSystem.get(conf);
        Path path = new Path("/user/hadoop");
        getFile(path,fs);
        //fs.close();
    }
     
    public static void getFile(Path path,FileSystem fs) throws IOException {
         
        FileStatus[] fileStatus = fs.listStatus(path);
        for(int i=0;i<fileStatus.length;i++){
            if(fileStatus[i].isDir()){
                Path p = new Path(fileStatus[i].getPath().toString());
                getFile(p,fs);
            }else{
                System.out.println(fileStatus[i].getPath().toString());
            }
        }
    }
 
}

8、查找某个文件在HDFS集群的位置

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import java.io.IOException;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.BlockLocation;
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 FindFile {
     
    public static void main(String[] args) throws IOException {
        getFileLocal();
    }
     
    /**
     * 查找某个文件在HDFS集群的位置
     * @Title: 
     * @Description:
     * @param
     * @return
     * @throws
     */
    public static void getFileLocal() throws IOException{
        Configuration conf = new Configuration();
        FileSystem fs = FileSystem.get(conf);
        Path path = new Path("/user/hadoop/hdfs/xxxx.txt");
         
        FileStatus status = fs.getFileStatus(path);
        BlockLocation[] locations = fs.getFileBlockLocations(status, 0, status.getLen());
         
        int length = locations.length;
        for(int i=0;i<length;i++){
            String[] hosts = locations[i].getHosts();
            System.out.println("block_" + i + "_location:" + hosts[i]);
        }
    }
     
}

9、HDFS集群上所有节点名称信息

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package com.hadoop.file;
 
import java.io.IOException;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.BlockLocation;
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 FindFile {
     
    public static void main(String[] args) throws IOException {
        getHDFSNode();
    }
     
    /**
     * HDFS集群上所有节点名称信息
     * @Title: 
     * @Description:
     * @param
     * @return
     * @throws
     */
    public static void getHDFSNode() throws IOException{
        Configuration conf = new Configuration();
        FileSystem fs = FileSystem.get(conf);
 
        DistributedFileSystem  dfs = (DistributedFileSystem)fs;
        DatanodeInfo[] dataNodeStats = dfs.getDataNodeStats();
         
        for(int i=0;i<dataNodeStats.length;i++){
            System.out.println("DataNode_" + i + "_Node:" + dataNodeStats[i].getHostName());
        }
         
    }
     
     
}

 

伪分布环境下操作FileSystem时候会出现异常：　　

Java代码如下：

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FileSystem fs = FileSystem.get(conf);
in = fs.open(new Path("hdfs://localhost:9000/wzqSearchEngine/crawl/inject_in"));

 

抛出异常如下：

    Exception in thread "main" java.lang.IllegalArgumentException: Wrong FS: hdfs://localhost:9000/wzqSearchEngine/crawl/inject_in, expected: file:/// 
        at org.apache.hadoop.fs.FileSystem.checkPath(FileSystem.java:310) 
        at org.apache.hadoop.fs.RawLocalFileSystem.pathToFile(RawLocalFileSystem.java:47) 
        at org.apache.hadoop.fs.RawLocalFileSystem.getFileStatus(RawLocalFileSystem.java:357) 
        at org.apache.hadoop.fs.FilterFileSystem.getFileStatus(FilterFileSystem.java:245) 
        at org.apache.hadoop.fs.ChecksumFileSystem$ChecksumFSInputChecker.<init>(ChecksumFileSystem.java:125) 
        at org.apache.hadoop.fs.ChecksumFileSystem.open(ChecksumFileSystem.java:283) 
        at org.apache.hadoop.fs.FileSystem.open(FileSystem.java:356) 
        at com.netease.hadoop.HDFSCatWithAPI.main(HDFSCatWithAPI.java:23) 

解决方案：
将hadoop的core-site.xml和hdfs-site.xml放到当前工程下（Eclipse工作目录的bin文件夹下面）即可。

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总结：

因为是访问远程的HDFS 需要通过URI来获得FileSystem。　　

　　

　　

　　

　　

　　

　　

　　

Hadoop HDFS文件操作的Java代码,布布扣,bubuko.com

原文：http://www.cnblogs.com/wuzhenquan/p/3617751.html

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