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 package org.apache.hadoop.fs; 019 020 import org.apache.commons.codec.binary.Base64; 021 import org.apache.commons.lang.builder.EqualsBuilder; 022 import org.apache.commons.lang.builder.HashCodeBuilder; 023 import org.apache.hadoop.classification.InterfaceAudience; 024 import org.apache.hadoop.classification.InterfaceStability; 025 026 /** 027 * HDFS-specific volume identifier which implements {@link VolumeId}. Can be 028 * used to differentiate between the data directories on a single datanode. This 029 * identifier is only unique on a per-datanode basis. 030 * 031 * Note that invalid IDs are represented by {@link VolumeId#INVALID_VOLUME_ID}. 032 */ 033 @InterfaceStability.Unstable 034 @InterfaceAudience.Public 035 public class HdfsVolumeId implements VolumeId { 036 037 private final byte[] id; 038 039 public HdfsVolumeId(byte[] id) { 040 if (id == null) { 041 throw new NullPointerException("A valid Id can only be constructed " + 042 "with a non-null byte array."); 043 } 044 this.id = id; 045 } 046 047 @Override 048 public final boolean isValid() { 049 return true; 050 } 051 052 @Override 053 public int compareTo(VolumeId arg0) { 054 if (arg0 == null) { 055 return 1; 056 } 057 if (!arg0.isValid()) { 058 // any valid ID is greater 059 // than any invalid ID: 060 return 1; 061 } 062 return hashCode() - arg0.hashCode(); 063 } 064 065 @Override 066 public int hashCode() { 067 return new HashCodeBuilder().append(id).toHashCode(); 068 } 069 070 @Override 071 public boolean equals(Object obj) { 072 if (obj == null || obj.getClass() != getClass()) { 073 return false; 074 } 075 if (obj == this) { 076 return true; 077 } 078 HdfsVolumeId that = (HdfsVolumeId) obj; 079 // NB: if (!obj.isValid()) { return false; } check is not necessary 080 // because we have class identity checking above, and for this class 081 // isValid() is always true. 082 return new EqualsBuilder().append(this.id, that.id).isEquals(); 083 } 084 085 @Override 086 public String toString() { 087 return Base64.encodeBase64String(id); 088 } 089 }