Initializing the HDFS

// Complete initialization and authentication.
 confLoad();
 authentication();
 // Creating a sample project 
 HdfsExample hdfs_examples = new HdfsExample("/user/hdfs-examples", "test.txt");


 /**
  * 
  * If the application is running in the Linux OS, the path of core-site.xml, hdfs-site.xml must be modified to the absolute path of the client file in the Linux OS. 
  *
  * 
  */  
 private static void confLoad() throws IOException {
   conf = new Configuration();
   // conf file
   conf.addResource(new Path(PATH_TO_HDFS_SITE_XML));
   conf.addResource(new Path(PATH_TO_CORE_SITE_XML));
   // conf.addResource(new Path(PATH_TO_SMALL_SITE_XML));
 }

 /**
  *Safety authentication 
  *
  */
 private static void authentication() throws IOException {
   // security mode
   if ("kerberos".equalsIgnoreCase(conf.get("hadoop.security.authentication"))) {
     System.setProperty("java.security.krb5.conf", PATH_TO_KRB5_CONF);
     LoginUtil.login(PRNCIPAL_NAME, PATH_TO_KEYTAB, PATH_TO_KRB5_CONF, conf);
   }
 }
 /**
  *Create a sample project. 
  */
 public HdfsExample(String path, String fileName) throws IOException  {
   this.DEST_PATH = path;
   this.FILE_NAME = fileName;
   instanceBuild();
 }

 private void instanceBuild() throws IOException {
   fSystem = FileSystem.get(conf);

The login example codes need to be added for the first login when applications are run in both Windows and Linux. For details on the example codes, see the LoginUtil class in com.huawei.hadoop.security.

public synchronized static void login(String userPrincipal, String userKeytabPath, String krb5ConfPath, Configuration conf)
        throws IOException
    {
        // 1.Check the input parameters. 

        if ((userPrincipal == null) || (userPrincipal.length() <= 0))
        {
            LOG.error("input userPrincipal is invalid.");
            throw new IOException("input userPrincipal is invalid.");
        }
        
        if ((userKeytabPath == null) || (userKeytabPath.length() <= 0))
        {
            LOG.error("input userKeytabPath is invalid.");
            throw new IOException("input userKeytabPath is invalid.");
        }
                
        if ((krb5ConfPath == null) || (krb5ConfPath.length() <= 0))
        {
            LOG.error("input krb5ConfPath is invalid.");
            throw new IOException("input krb5ConfPath is invalid.");
        }
        
        if ((conf == null))
        {
            LOG.error("input conf is invalid.");
            throw new IOException("input conf is invalid.");
        }
        
        // 2.Check whether the file exists.

        File userKeytabFile = new File(userKeytabPath);
        if (!userKeytabFile.exists())
        {
            LOG.error("userKeytabFile(" + userKeytabFile.getAbsolutePath() + ") does not exsit.");
            throw new IOException("userKeytabFile(" + userKeytabFile.getAbsolutePath() + ") does not exsit.");
        }
        if (!userKeytabFile.isFile())
        {
            LOG.error("userKeytabFile(" + userKeytabFile.getAbsolutePath() + ") is not a file.");
            throw new IOException("userKeytabFile(" + userKeytabFile.getAbsolutePath() + ") is not a file.");
        }
        
        File krb5ConfFile = new File(krb5ConfPath);
        if (!krb5ConfFile.exists())
        {
            LOG.error("krb5ConfFile(" + krb5ConfFile.getAbsolutePath() + ") does not exsit.");
            throw new IOException("krb5ConfFile(" + krb5ConfFile.getAbsolutePath() + ") does not exsit.");
        }
        if (!krb5ConfFile.isFile())
        {
            LOG.error("krb5ConfFile(" + krb5ConfFile.getAbsolutePath() + ") is not a file.");
            throw new IOException("krb5ConfFile(" + krb5ConfFile.getAbsolutePath() + ") is not a file.");
        }
        
        // 3.Set and check krb5config. 

        setKrb5Config(krb5ConfFile.getAbsolutePath());        
        setConfiguration(conf);
        
        // 4.Log in to Hadoop to check items.

        loginHadoop(userPrincipal, userKeytabFile.getAbsolutePath());
        LOG.info("Login success!!!!!!!!!!!!!!");
}