org.musicontroller.core
Class EventCountLookup

java.lang.Object
  org.musicontroller.core.EventCountLookup

public class EventCountLookup
extends java.lang.Object

A class for quick eventcount lookup. Songs can have any number of Events. Counting Events, which happens a lot in MusiController, is relatively slow. Events are lazily loaded by Hibernate, thus a call to getEvents() causes an additional DB-access. Caching Events would be a solution, but is not very realistic, because of the sheer amount of them. Since we're mostly interested in counts, this class helps us.

The EventCountLookup takes up only 8 integers and a Date of memory per Song and User. Therefore, caching makes sense for this object. This class contains a LRU-list, to which all lookup-tables are added.

Author:

Varienaja

Field Summary

protected static int

CACHESIZE

Method Summary

void	addEvent(Event event) Updates this EventCountLookup object with a new Event.
static EventCountLookup	create(java.util.Set<Event> events, long songid) Factory method, which returns an EventCountLookup object.
int	getEventCount(long userid, int kind) Returns the amount of Events of a certain type.
int	getEventCountLastYear(long userid, int kind) Returns the amount of Events of a certain type, which took place in the last year.
java.util.Date	getLastPlay(long userid) Looks up the Date of the latest Play-Event.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

CACHESIZE

protected static final int CACHESIZE

See Also:

Constant Field Values

Method Detail

create

public static EventCountLookup create(java.util.Set<Event> events,
                                      long songid)

Factory method, which returns an EventCountLookup object. When a cached object is found, it is returned, otherwise a new object is created and added to the cache.

Parameters:

events - The Set of Events, for the Song. (Only accessed when a new EventCountLookup-object must be created. When a cached object is found, the Events are not touched, so that they can stay uninitialized when they were lazily loaded.)

songid - The id of the Song.

Returns:

An initialized EventCountLookup-object.

addEvent

public void addEvent(Event event)

Updates this EventCountLookup object with a new Event.

Parameters:

event - The new Event.

getEventCount

public int getEventCount(long userid,
                         int kind)

Returns the amount of Events of a certain type.

Parameters:

userid - The user to look these Events up for.

kind - The type of Events to look the count up for.

Returns:

The amount of Events.

getEventCountLastYear

public int getEventCountLastYear(long userid,
                                 int kind)

Returns the amount of Events of a certain type, which took place in the last year.

Parameters:

userid - The user to look these Events up for.

kind - The type of Events to look the count up for.

Returns:

The amount of Events.

getLastPlay

public java.util.Date getLastPlay(long userid)

Looks up the Date of the latest Play-Event.

Parameters:

userid - The user to look this Date up for.

Returns:

The Date when this User plays this song for the last time. ( Or null when never played.)