使用kerberos下安全Hadoop時，通常是在linux系統下使用kinit命令進行身份認證，下面提供一種在java api中認證的方式：

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FSDataInputStream;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.security.SecurityUtil;
import org.apache.hadoop.security.UserGroupInformation;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
/**
 * Created by sure on 15-5-12.
 */
public class HdfsKerberos {
    static Configuration conf = new Configuration();
    public static void main(String[] args) throws IOException {
        //keytab檔案的路徑
        conf.set(KEYTAB_FILE_KEY, "/opt/sure.keytab");
        //principal
        conf.set(USER_NAME_KEY, "sure");
        login(conf);
        System.out.println(loadHdfsFile("/trident/trident-1-0-1431409180775.txt"));
    }
    public static List<String> loadHdfsFile(String filePath){
        List<String> resultList = new ArrayList<>();
        FileSystem fileSystem = null;
        try {
            fileSystem = FileSystem.get(conf);
            FSDataInputStream fs = fileSystem.open(new Path(filePath));
            BufferedReader bis = new BufferedReader(new InputStreamReader(fs,"UTF-8"));
            String line;
            while ((line = bis.readLine()) != null) {
                resultList.add(line);
            }
            fileSystem.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return resultList;
    }
    public static final String KEYTAB_FILE_KEY = "hdfs.keytab.file";
    public static final String USER_NAME_KEY = "hdfs.kerberos.principal";
    public static void login(Configuration hdfsConfig) throws IOException {
        if (UserGroupInformation.isSecurityEnabled()) {
            String keytab = conf.get(KEYTAB_FILE_KEY);
            if (keytab != null) {
                hdfsConfig.set(KEYTAB_FILE_KEY, keytab);
            }
            String userName = conf.get(USER_NAME_KEY);
            if (userName != null) {
                hdfsConfig.set(USER_NAME_KEY, userName);
            }
            SecurityUtil.login(hdfsConfig, KEYTAB_FILE_KEY, USER_NAME_KEY);
        }
    }
}