EDIT

/**

* Copyright (C) 2007 EDIT

* European Distributed Institute of Taxonomy 

* http://www.e-taxonomy.eu

* 

* The contents of this file are subject to the Mozilla Public License Version 1.1

* See LICENSE.TXT at the top of this package for the full license terms.

*/

package eu.etaxonomy.cdm.model.common;

import eu.etaxonomy.cdm.model.agent.Person;

import org.apache.log4j.Logger;

import org.hibernate.annotations.Cascade;

import org.hibernate.annotations.CascadeType;

import java.util.*;

import javax.persistence.*;

import javax.xml.bind.annotation.XmlAccessType;

import javax.xml.bind.annotation.XmlAccessorType;

import javax.xml.bind.annotation.XmlElement;

import javax.xml.bind.annotation.XmlRootElement;

import javax.xml.bind.annotation.XmlTransient;

import javax.xml.bind.annotation.XmlType;

/**

 * The class keeps track of versions via a full linked list to different version objects, or a simple updated/updatedBy property in the same object.

 * 

 * Full versioning allows concrete subclasses to keep track of previous or later versions of an object.

 * A different version is another (persistent) java object, but with the same UUID. 

 * The version history is established as a linked list of the version objects in time.

 * If versioning via the linked list is used, updated/updatedBy is the same as created/createdBy (better NULL?).

 * 

 * Versioning can be turned off and in this case this class provides updated/updatedBy to keep track of the latest change event.

 * 

 * @author m.doering

 * @created 08-Nov-2007 13:07:01

 *

 * @param <T>

 */

@XmlAccessorType(XmlAccessType.FIELD)

@XmlType(name = "VersionableEntity", propOrder = {

//    "updated",

    "updatedBy",

    "nextVersion",

    "previousVersion"

})

@XmlRootElement(name = "VersionableEntity")

@MappedSuperclass

public abstract class VersionableEntity<T extends VersionableEntity> extends CdmBase {

	private static final Logger logger = Logger.getLogger(VersionableEntity.class);

	//time of last update for this object

	// There is a problem with "updated" during deserialization because of the @Version annotation.

	@XmlTransient

	//@XmlElement(name ="Updated")

	private Calendar updated;

	@XmlElement(name = "UpdatedBy")

	private Person updatedBy;

	@XmlElement(name = "NextVersion")

	private T nextVersion;

	@XmlElement(name = "PreviousVersion")

	private T previousVersion;

	/**

	 * Returns the succeeding version of this object with the same UUID

	 * @return next, i.e. succeeding version of this object

	 */

	//@OneToOne(mappedBy="previousVersion")

	@Transient

	public T getNextVersion(){

		return this.nextVersion;

	}

	public void setNextVersion(T nextVersion){

		this.nextVersion = nextVersion;

	}

	//@OneToOne

	@Transient

	public T getPreviousVersion(){

		return this.previousVersion;

	}

	public void setPreviousVersion(T previousVersion){

		this.previousVersion = previousVersion;

	}

	@ManyToOne(fetch=FetchType.LAZY)

	@Cascade({CascadeType.SAVE_UPDATE})

	public Person getUpdatedBy(){

		return this.updatedBy;

	}

	/**

	 * 

	 * @param updatedBy    updatedBy

	 */

	public void setUpdatedBy(Person updatedBy){

		this.updatedBy = updatedBy;

	}

	/**

	 * 

	 * @return

	 */

	@Temporal(TemporalType.TIMESTAMP)

	@Version

	@Basic(fetch = FetchType.LAZY)

	public Calendar getUpdated(){

		return this.updated;

	}

	/**

	 * 

	 * @param updated    updated

	 */

	public void setUpdated(Calendar updated){

		this.updated = updated;

	}

	/**

	 * based on created

	 */

	@Transient

	public Calendar getValidFrom(){

		return null;

	}

	/**

	 * based on updated

	 */

	@Transient

	public Calendar getValidTo(){

		return null;

	}

	/**

	 * Is true if UUID and created timestamp are the same for the passed Object and this one.

	 * @see eu.etaxonomy.cdm.model.common.CdmBase#equals(java.lang.Object)

	 * See {@link http://www.hibernate.org/109.html hibernate109}, {@link http://www.geocities.com/technofundo/tech/java/equalhash.html geocities} 

	 * or {@link http://www.ibm.com/developerworks/java/library/j-jtp05273.html ibm}

	 * for more information about equals and hashcode. 

	 */

	@Override

	public boolean equals(Object obj) {

		if (obj == this){

			return true;

		}

		if (obj == null){

			return false;

		}

		if (!CdmBase.class.isAssignableFrom(obj.getClass())){

			return false;

		}

		ICdmBase cdmObj = (ICdmBase)obj;

		boolean uuidEqual = cdmObj.getUuid().equals(this.getUuid());

		boolean createdEqual = cdmObj.getCreated().equals(this.getCreated());

		if (! uuidEqual || !createdEqual){

				return false;

		}

		return true;

	}

	/** Overrides {@link eu.etaxonomy.cdm.model.common.CdmBase#hashCode()}

	 *  See {@link http://www.hibernate.org/109.html}, {@link http://www.geocities.com/technofundo/tech/java/equalhash.html} 

	 * or {@link http://www.ibm.com/developerworks/java/library/j-jtp05273.html}

	 * for more information about equals and hashcode. 

	 */

	 @Override

	public int hashCode() {

		   int hashCode = 7;

		   hashCode = 29 * hashCode + this.getUuid().hashCode();

		   //hashCode = 29 * hashCode + this.getCreated().hashCode();

		   return hashCode;

	}

//********************** CLONE *****************************************/

	/** 

	 * Clones this versionable entity.

	 * Set fields for nextVersion, previousVersion, updated, updatedBy and createdBy are set to <tt>null</tt>

	 * The id is set to 0.

	 * The uuid is created new.

	 * The createdWhen is set to the current date.

	 * @see java.lang.Object#clone()

	 */

	@Override

	public Object clone() throws CloneNotSupportedException{

		VersionableEntity result = (VersionableEntity)super.clone();

		//TODO ?

		result.setNextVersion(null);

		result.setPreviousVersion(null);

		result.setUpdated(null);

		result.setUpdatedBy(null);

		//no changes to: -

		return result;

	}

}