/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*/
package org.apache.isis.core.metamodel.adapter.version;
import java.io.IOException;
import java.io.Serializable;
import java.util.Date;
import org.apache.isis.core.commons.encoding.DataInputExtended;
import org.apache.isis.core.commons.encoding.DataOutputExtended;
import org.apache.isis.core.commons.encoding.Encodable;
import org.apache.isis.core.commons.lang.DateExtensions;
import org.apache.isis.core.metamodel.adapter.ObjectAdapter;
import org.apache.isis.core.metamodel.adapter.oid.OidMarshaller;
/**
* An instance of this class is held by each {@link ObjectAdapter} and is used
* to represent a particular version (at a point in time) of domain object
* wrapped by that adapter.
*
* <p>
* This is normally done using some form of incrementing number or timestamp,
* which would be held within the implementing class. The numbers, timestamps,
* etc should change for each changed object, and the different() method should
* indicate that the two Version objects are different.
*
* <p>
* The user's name and a timestamp should alos be kept so that when an message
* is passed to the user it can be of the form "user has change object at time"
*/
public class Version implements Serializable, Encodable {
private static final long serialVersionUID = 1L;
private final static OidMarshaller OID_MARSHALLER = OidMarshaller.INSTANCE;
//region > factory methods
public static Version create(final Long sequence) {
return create(sequence, null, (Long)null);
}
public static Version create(String sequence, String user, String utcTimestamp) {
if(sequence == null) {
return null;
}
return create(Long.parseLong(sequence), user, utcTimestamp != null?Long.parseLong(utcTimestamp):null);
}
public static Version create(final Long sequence, final String user, final Date time) {
return create(sequence, user, time !=null? time.getTime(): null);
}
public static Version create(Long sequence, String user, Long utcTimestamp) {
if(sequence == null) {
return null;
}
return new Version(sequence, user, utcTimestamp);
}
//endregion
//region > constructor, fields
private final Long sequence;
private final String user;
private final Long utcTimestamp;
private Version(Long sequence, String user, Long utcTimestamp) {
this.sequence = sequence;
this.user = user;
this.utcTimestamp = utcTimestamp;
}
//endregion
//region > encodable
public Version(final DataInputExtended input) throws IOException {
this(input.readLong(), input.readUTF(), input.readLong());
}
@Override
public void encode(final DataOutputExtended output) throws IOException {
output.writeLong(sequence);
output.writeUTF(user);
output.writeLong(utcTimestamp);
}
//endregion
//region > getters
/**
* The internal, strictly monotonically increasing, version number.
*
* <p>
* This might be the timestamp of the change, or it might be simply a number incrementing 1,2,3...
*/
public long getSequence() {
return sequence;
}
/**
* Returns the user who made the last change (used for display/reporting only)
*
* <p>
* May be null.
*/
public String getUser() {
return user;
}
/**
* The time of the last change, as UTC milliseconds.
*
* <p>
* May be null.
*
* @see #getTime()
*/
public Long getUtcTimestamp() {
return utcTimestamp;
}
/**
* Returns the time of the last change (used for display/reporting only, not comparison)
*
* <p>
* May be null.
*
* @see #getUtcTimestamp()
*/
public Date getTime() {
return utcTimestamp != null? new Date(this.utcTimestamp): null;
}
//endregion
//region > enString
public String enString() {
return OID_MARSHALLER.marshal(this);
}
//endregion
//region > equals, hashCode
@Override
public int hashCode() {
final int prime = 31;
int result = 1;
result = prime * result + ((sequence == null) ? 0 : sequence.hashCode());
return result;
}
@Override
public boolean equals(Object obj) {
if (this == obj)
return true;
if (obj == null)
return false;
if (getClass() != obj.getClass())
return false;
Version other = (Version) obj;
if (sequence == null) {
if (other.sequence != null)
return false;
} else if (!sequence.equals(other.sequence))
return false;
return true;
}
/**
* Compares this version against the specified version and returns true if
* they are different versions (by checking {@link #getSequence()}).
*
* <p>
* This is use for optimistic checking, where the existence of a different
* version will normally cause a concurrency exception.
*/
public boolean different(Version version) {
return !equals(version);
}
//endregion
//region > sequence
@Override
public String toString() {
return "#" + sequence + " " + getUser() + " " + DateExtensions.asTimestamp(getTime());
}
/**
* Returns the sequence for printing/display
*/
public String sequence() {
return Long.toString(sequence, 16);
}
//endregion
}