org.nerd4j.utils.cache

Class AbstractSelfLoadingCache<V>

java.lang.Object

org.nerd4j.utils.cache.AbstractSelfLoadingCache<V>

Type Parameters:

V - type of the data model to cache.

All Implemented Interfaces:

SelfLoadingCache<V>

public abstract class AbstractSelfLoadingCache<V>
extends Object
implements SelfLoadingCache<V>

Abstract implementation of SelfLoadingCache.

This class provides most of the common logic and some useful extension hooks. Any custom implementation of the SelfLoadingCache interface should extend this class.

Since:

2.0.0

Author:

Massimo Coluzzi

Field Summary

Fields

Modifier and Type	Field and Description
protected CacheProvider<V>	cacheProvider Underlying caching system provider.
protected CacheConfig	config Configurations to be used to define the cache behavior.
protected boolean	disabledThis Tells if this SelfLoadingCache is disabled.
protected static ExecutorService	executorService The ExecutorService to use to insert or update cache entries in an asynchronous way.
static Logger	logger Logging system.

Constructor Summary

Constructors

Constructor and Description
AbstractSelfLoadingCache(CacheConfig cacheConfig, CacheProvider<V> cacheProvider) Constructor with parameters.

Method Summary

Modifier and Type	Method and Description
void	disableThis(boolean disable) Invoking this method with true will disable this SelfLoadingCache instance.
void	evict(CacheKey key) Removes the given key from the underlying cache system forcing to reload it the next time SelfLoadingCache.get(CacheKey, DataProvider) is invoked.
protected CacheEntry<V>	get(CacheKey key) Returns the value from the cache if available and null otherwise.
V	get(CacheKey key, DataProvider<V> dataProvider) Returns the value related to the given key.
protected V	insert(CacheKey key, DataProvider<V> dataProvider) Inserts the given key and the related value into the cache.
protected V	load(CacheKey key, DataProvider<V> dataProvider) Loads the value from the DataProvider.
protected V	loadAndPut(String operation, CacheKey key, DataProvider<V> dataProvider) Performs the loading of te data related to the given key and puts the <key-value> pair into the cache.
protected void	put(CacheKey key, V value) Puts the given key-value pair into the cache.
protected V	update(CacheKey key, CacheEntry<V> entry, DataProvider<V> dataProvider) Updates the cache for the given key and the related value.

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.nerd4j.utils.cache.SelfLoadingCache

disableAll

Field Detail

logger

public static final Logger logger

Logging system.

By default the logging level is Level.WARNING and will only log exceptions.

If you want to log any caching operation you need to set the logging level to Level.INFO.

If you want to dig into deeper detail about cache loading and updating operations, you need to set the logging level to Level.FINE.

If you want to log everything is happening in the cache, including the data that is going to be cached, you need to set the logging level to Level.FINEST.

If you trust this class to work properly and you do not want your console output to get dirty you can turn off this log by setting the logging level to Level.OFF.

To change the Logger levels and outputs follow the Java documentation.

executorService

protected static final ExecutorService executorService

The ExecutorService to use to insert or update cache entries in an asynchronous way.

config

protected final CacheConfig config

Configurations to be used to define the cache behavior.

cacheProvider

protected final CacheProvider<V> cacheProvider

Underlying caching system provider.

disabledThis

protected boolean disabledThis

Tells if this SelfLoadingCache is disabled. If this flag is set to true this instance will skip any caching operation and all data will be loaded on each request.

This option should be used to debugging purposes only, using this option in production can be very dangerous.

Constructor Detail

AbstractSelfLoadingCache

public AbstractSelfLoadingCache(CacheConfig cacheConfig,
                                CacheProvider<V> cacheProvider)

Constructor with parameters.

Parameters:

cacheConfig - configurations to be used to define the cache behavior.

cacheProvider - underlying caching system provider.

Method Detail

disableThis

public void disableThis(boolean disable)

Invoking this method with true will disable this SelfLoadingCache instance. All the caching will be skipped and all data will be loaded from the DataProvider on each request.

This option should be used to debugging purposes only, using this option in production can be very dangerous.

Invoking this method with false will restore the caching process.

Specified by:

disableThis in interface SelfLoadingCache<V>

Parameters:

disable - tells if this SelfLoadingCache instance needs to stop all caching operations.

get

public V get(CacheKey key,
             DataProvider<V> dataProvider)

Returns the value related to the given key.

If the given key is not present in the cache or the related entry is expired the given DataProvider will be used to retrieve the data to store into the cache.

Specified by:

get in interface SelfLoadingCache<V>

Parameters:

key - the key to search for.

dataProvider - the provider of the information to cache.

Returns:

the value related to the given key, can be null.

evict

public void evict(CacheKey key)

Removes the given key from the underlying cache system forcing to reload it the next time SelfLoadingCache.get(CacheKey, DataProvider) is invoked.

Specified by:

evict in interface SelfLoadingCache<V>

Parameters:

key - key to be evicted.

get

protected CacheEntry<V> get(CacheKey key)

Returns the value from the cache if available and null otherwise.

This method returns null in both cases:

1. If the cache provider returns null.
2. If the cache provider throws an exception.

Parameters:

key - the key to search for.

Returns:

the cached entry or null.

Throws:

CacheProviderException - if an error occurred during cache operations and the flag CacheConfig.isThrowCacheProviderExceptions() is true.

put

protected void put(CacheKey key,
                   V value)

Puts the given key-value pair into the cache.

Parameters:

key - the key to cache.

value - the value to cache.

Throws:

CacheProviderException - if an error occurred during cache operations and the flag CacheConfig.isThrowCacheProviderExceptions() is true.

load

protected V load(CacheKey key,
                 DataProvider<V> dataProvider)

Loads the value from the DataProvider.

Parameters:

key - the key to search for.

dataProvider - the DataProvider to invoke.

Returns:

the data to cache.

Throws:

DataProviderException - if there is a failure in the data loading.

loadAndPut

protected V loadAndPut(String operation,
                       CacheKey key,
                       DataProvider<V> dataProvider)

Performs the loading of te data related to the given key and puts the <key-value> pair into the cache.

Parameters:

operation - the operation to log.

key - key to cache.

dataProvider - provider of the values to be cached.

Returns:

the loaded value.

Throws:

CacheProviderException - if an error occurred during cache operations and the flag CacheConfig.isThrowCacheProviderExceptions() is true.

DataProviderException - if there is a failure in the data loading.

insert

protected V insert(CacheKey key,
                   DataProvider<V> dataProvider)

Inserts the given key and the related value into the cache.

If this cache is configured to perform inserts synchronously (the default) then this method will invoke loadAndPut(String,CacheKey,DataProvider), otherwise the insert will be performed by another thread while this method returns null.

Parameters:

key - key to cache.

dataProvider - provider of the values to be cached.

Returns:

the inserted value, or null.

Throws:

CacheProviderException - if an error occurred during cache operations and the flag CacheConfig.isThrowCacheProviderExceptions() is true.

DataProviderException - if there is a failure in the data loading.

update

protected V update(CacheKey key,
                   CacheEntry<V> entry,
                   DataProvider<V> dataProvider)

Updates the cache for the given key and the related value.

If this cache is configured to perform updates asynchronously (the default) then the update will be performed by another thread while this method returns the current cached value, otherwise this method will invoke {#loadAndPut(String,CacheKey,DataProvider)} and return the fresh loaded value.

If multiple threads try to update the same key only one will succeed, all the other will return the currently cached value.

Parameters:

key - key to cache.

entry - the expired cache entry.

dataProvider - provider of the values to be cached.

Returns:

the fresh loaded value, or the cached one.

Throws:

CacheProviderException - if an error occurred during cache operations and the flag CacheConfig.isThrowCacheProviderExceptions() is true.

DataProviderException - if there is a failure in the data loading.