hdfs2.9.0简单开发

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1、maven工程的构建，hadoop用的版本是2.9.0。jdk的版本为1.8.0_131

<!-- https://mvnrepository.com/artifact/org.apache.hadoop/hadoop-hdfs --><dependency><groupId>org.apache.hadoop</groupId><artifactId>hadoop-hdfs</artifactId><version>2.9.0</version></dependency>

<!-- https://mvnrepository.com/artifact/org.apache.hadoop/hadoop-common --><dependency><groupId>org.apache.hadoop</groupId><artifactId>hadoop-common</artifactId><version>2.9.0</version><exclusions><exclusion><groupId>jdk.tools</groupId><artifactId>jdk.tools</artifactId></exclusion></exclusions></dependency>

<!-- https://mvnrepository.com/artifact/org.apache.hadoop/hadoop-client --><dependency><groupId>org.apache.hadoop</groupId><artifactId>hadoop-client</artifactId><version>2.9.0</version></dependency>

<dependency><groupId>jdk.tools</groupId><artifactId>jdk.tools</artifactId><version>1.8.0_131</version><scope>system</scope><systemPath>${JAVA_HOME}/lib/tools.jar</systemPath></dependency>

2、对 hdfs的简单操作

    //文件系统    FileSystem fileSystem;

   //初始化文件系统    public void init() throws Exception{        //读取数据由平台上的协议确定        URI uri = new URI("hdfs://dtbigdata:9000");        Configuration conf = new Configuration();        fileSystem = FileSystem.get(uri, conf);    }

    //查看目录    public void Catalog() throws Exception{        Path path = new Path("/user");        FileStatus fileStatus = fileSystem.getFileStatus(path);        System.out.println("*************************************");            System.out.println("文件根目录: "+fileStatus.getPath());         System.out.println("这文件目录为：");        for(FileStatus fs : fileSystem.listStatus(path)){             System.out.println(fs.getPath());         }     }

    //浏览文件    public void look() throws Exception{        Path path = new Path("/user/root/b.txt");        FSDataInputStream fsDataInputStream = fileSystem.open(path);        System.out.println("*************************************");        System.out.println("浏览文件的内容：");        int c;        while((c = fsDataInputStream.read()) != -1){            System.out.print((char)c);            }        fsDataInputStream.close();    }

     //下载    public void download() throws Exception{        //下载路径    String file = "D://hadoop.txt";        InputStream in = fileSystem.open(new Path("/user/root/b.txt"));          OutputStream out = new FileOutputStream(file);          IOUtils.copyBytes(in, out, 4096, true);          System.out.println("*************************************");        System.out.println("文件下载完成！"+file);    }

    //上传文件    public void upload() throws Exception{        Path srcPath = new Path("F:/b.txt");          Path dstPath = new Path("/user/root");          fileSystem.copyFromLocalFile(false, srcPath, dstPath);        fileSystem.close();         System.out.println("*************************************");        System.out.println("上传成功！");    }

    //删除文件    public void delete() throws Exception{        Path path = new Path("/user/root/a.txt");        fileSystem.delete(path,true);        System.out.println("*************************************");        System.out.println("删除成功！");    }

3、代码的运行

3.1、会出现错误 Permission denied: user=Administrator

是因为在windows下运行，默认用户为 Administrator，该用户没有权限。

3.2、最快速的解决方法

        -DHADOOP_USER_NAME=root

添加位置方法如下：

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