001/**
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *     http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing, software
013 * distributed under the License is distributed on an "AS IS" BASIS,
014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015 * See the License for the specific language governing permissions and
016 * limitations under the License.
017 */
018
019package org.apache.hadoop.security.token;
020
021import java.io.IOException;
022import java.util.Arrays;
023
024import org.apache.commons.codec.digest.DigestUtils;
025import org.apache.hadoop.classification.InterfaceAudience;
026import org.apache.hadoop.classification.InterfaceStability;
027import org.apache.hadoop.io.DataOutputBuffer;
028import org.apache.hadoop.io.Text;
029import org.apache.hadoop.io.Writable;
030import org.apache.hadoop.security.UserGroupInformation;
031
032/**
033 * An identifier that identifies a token, may contain public information 
034 * about a token, including its kind (or type).
035 */
036@InterfaceAudience.Public
037@InterfaceStability.Evolving
038public abstract class TokenIdentifier implements Writable {
039
040  private String trackingId = null;
041
042  /**
043   * Get the token kind
044   * @return the kind of the token
045   */
046  public abstract Text getKind();
047
048  /**
049   * Get the Ugi with the username encoded in the token identifier
050   * 
051   * @return the username. null is returned if username in the identifier is
052   *         empty or null.
053   */
054  public abstract UserGroupInformation getUser();
055
056  /**
057   * Get the bytes for the token identifier
058   * @return the bytes of the identifier
059   */
060  public byte[] getBytes() {
061    DataOutputBuffer buf = new DataOutputBuffer(4096);
062    try {
063      this.write(buf);
064    } catch (IOException ie) {
065      throw new RuntimeException("i/o error in getBytes", ie);
066    }
067    return Arrays.copyOf(buf.getData(), buf.getLength());
068  }
069
070  /**
071   * Returns a tracking identifier that can be used to associate usages of a
072   * token across multiple client sessions.
073   *
074   * Currently, this function just returns an MD5 of {{@link #getBytes()}.
075   *
076   * @return tracking identifier
077   */
078  public String getTrackingId() {
079    if (trackingId == null) {
080      trackingId = DigestUtils.md5Hex(getBytes());
081    }
082    return trackingId;
083  }
084}