lazyj.cache

Class GenericQueryCacher<K,V>

java.lang.Object

lazyj.cache.GenericQueryCacher<K,V>

Type Parameters:

K - key type

V - value type

All Implemented Interfaces:

CacheElement<K,V>, ReversableMultivaluesCache<K,V>, ReversableUniqueCache<K,V>

public abstract class GenericQueryCacher<K,V>
extends java.lang.Object
implements CacheElement<K,V>, ReversableMultivaluesCache<K,V>, ReversableUniqueCache<K,V>

Create a cache based on the resultset produced by a DB query.

Since:

2007-03-08

Author:

costing

Field Summary

Fields

Modifier and Type	Field and Description
protected java.util.Map<V,java.util.List<K>>	mReverse Reverse values
protected java.util.Map<K,V>	mValues Cache container

Constructor Summary

Constructors

Constructor and Description
GenericQueryCacher()

Method Summary

Methods

Modifier and Type	Method and Description
V	get(K key) The cached entry is most probably a hash of some sort.
protected abstract DBFunctions	getDB() Get a query loaded with a query that generates the key on the first column and the value on the second one.
K	getKeyForValue(V value) Reverse query, get the key associated with a value.
java.util.List<K>	getKeysForValue(V value)
java.util.Collection<V>	getValues() Get the values collection
java.util.Collection<K>	keySet() Get the key set
protected abstract K	readKey(DBFunctions db) Get the key object from the current DB row
protected abstract V	readValue(DBFunctions db) Get the value object from the current DB row
void	refresh() Update the contents of the cache entry.
int	size() Get the number of values in the forward map

Methods inherited from class java.lang.Object

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

Methods inherited from interface lazyj.cache.CacheElement

getRefreshTime

Field Detail

mValues

protected java.util.Map<K,V> mValues

Cache container

mReverse

protected java.util.Map<V,java.util.List<K>> mReverse

Reverse values

Constructor Detail

GenericQueryCacher

public GenericQueryCacher()

Method Detail

getDB

protected abstract DBFunctions getDB()

Get a query loaded with a query that generates the key on the first column and the value on the second one.

Returns:

a DBFunctions object loaded with a query

readKey

protected abstract K readKey(DBFunctions db)

Get the key object from the current DB row

Parameters:

db -

Returns:

key object

readValue

protected abstract V readValue(DBFunctions db)

Get the value object from the current DB row

Parameters:

db -

Returns:

value object

get

public final V get(K key)

Description copied from interface: CacheElement

The cached entry is most probably a hash of some sort. This is why the get() method is specified in this interface, to provide an easy and uniform way of retrieving the data between all the implementations.

Specified by:

get in interface CacheElement<K,V>

Parameters:

key - some unique key

Returns:

the value associated with that key, if any, or null.

getKeyForValue

public final K getKeyForValue(V value)

Description copied from interface: ReversableUniqueCache

Reverse query, get the key associated with a value.

Specified by:

getKeyForValue in interface ReversableUniqueCache<K,V>

Returns:

the key, if it exists, for this value

getKeysForValue

public final java.util.List<K> getKeysForValue(V value)

Specified by:

getKeysForValue in interface ReversableMultivaluesCache<K,V>

Returns:

all the keys that have this value associated with them

keySet

public java.util.Collection<K> keySet()

Get the key set

Returns:

the key set

getValues

public java.util.Collection<V> getValues()

Get the values collection

Returns:

collection of values

size

public int size()

Get the number of values in the forward map

Returns:

number of values

refresh

public final void refresh()

Description copied from interface: CacheElement

Update the contents of the cache entry. The implementation is application-dependent. Typically it involves filling an internal hash with some values from the database. But it can do whatever operation here, even something that doesn't involve actually caching anything, but just to execute a periodic task (cron style).

Specified by:

refresh in interface CacheElement<K,V>