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eFaps is a framework used to map objects with or without attached files to
a relational database and optional file systems (only for attaches files). Configurable access control can be provided down to object and attribute level depending on implementation and use case. Depending on requirements, events (like triggers) allow to implement business logic and to separate business logic from user interface.
The framework includes integrations (e.g. webdav, full text search) and a web application as 'simple' configurable user interface. Some best practises, example web application modules (e.g. team work module) support administrators and implementers using this framework.
/*
* Copyright 2003 - 2011 The eFaps Team
*
* Licensed 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.
*
* Revision: $Rev: 6210 $
* Last Changed: $Date: 2011-02-18 16:02:56 -0500 (Fri, 18 Feb 2011) $
* Last Changed By: $Author: [email protected] $
*/
package org.efaps.util.cache;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;
import java.util.UUID;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* The class is used to cache three not independent information which are
* completely defined once but needed many times within eFaps. An example
* is to load all types at startup and access the cached
* data instead of reading the cached information each time they are
* needed.
* If a reload of the cache is needed, the cached object could be accessed,
* but returns the "old" values until the old cache is replaced by
* the new read values.
* The class is thread save, but a cached instance could be accessed much
* faster than a synchronized hash map.
*
* @author The eFaps Team
* @param class implementing CacheObjectInterface
* @version $Id: AbstractCache.java 6210 2011-02-18 21:02:56Z [email protected] $
*/
public abstract class AbstractCache
{
/**
* Logging instance used to give logging information of this class.
*/
private static final Logger LOG = LoggerFactory.getLogger(AbstractCache.class);
/**
* Set that stores all initialized Caches.
*/
private static Set> CACHES = Collections.synchronizedSet(new HashSet>());
/**
* The map holds all cached data instances by Id. Because of the
* double-checked locking idiom, the instance variable is defined
* volatile.
*
* @see #get(Long)
*/
private volatile Map cache4Id = null;
/**
* The map holds all cached data instances by Name. Because of the
* double-checked locking idiom, the instance variable is defined
* volatile.
*
* @see #get(String)
*/
private volatile Map cache4Name = null;
/**
* The map holds all cached data instances by UUID. Because of the
* double-checked locking idiom, the instance variable is defined
* volatile.
*
* @see #get(UUID)
*/
private volatile Map cache4UUID = null;
/**
* Stores the class name of the class that initialized this cache.
*/
private String initializer;
/**
* Constructor adding this Cache to the set of Caches.
*/
protected AbstractCache()
{
AbstractCache.CACHES.add(this);
}
/**
* Returns for given key id the cached object from the cache4Id cache. If
* the cache was not initialized yet, null is returned.
*
* @see #getCache4Id()
* @param _id id of the searched cached object
* @return cached object
*
*/
public T get(final long _id)
{
return getCache4Id() == null ? null : getCache4Id().get(new Long(_id));
}
/**
* Returns for given key id the cached object from the cache4Id cache. If
* the cache was not initialized yet, null is returned.
*
* @see #getCache4Name()
* @param _name name the cached object
* @return cached object
*/
public T get(final String _name)
{
return getCache4Name() == null ? null : getCache4Name().get(_name);
}
/**
* Returns for given key id the cached object from the cache4Id cache. If
* the cache was not initialized yet, null is returned.
*
* @see #getCache4UUID()
* @param _uuid UUID of the cached object
* @return cached object
*
*/
public T get(final UUID _uuid)
{
return getCache4UUID() == null ? null : getCache4UUID().get(_uuid);
}
/**
* Add an object to this Cache. This method should only be used to add some
* objects, due to the reason that it is very slow!!! Normally the values
* should be added by using abstract method
* {@link #readCache(Map, Map, Map)}.
*
* @param _object Object to be added
*/
public void addObject(final T _object)
{
final Map newCache4Id = getNewCache4Id();
final Map newCache4Name = getNewCache4Name();
final Map newCache4UUID = getNewCache4UUID();
if (getCache4Id() != null) {
newCache4Id.putAll(getCache4Id());
}
if (getCache4Name() != null) {
newCache4Name.putAll(getCache4Name());
}
if (getCache4UUID() != null) {
newCache4UUID.putAll(getCache4UUID());
}
newCache4Id.put(_object.getId(), _object);
newCache4Name.put(_object.getName(), _object);
newCache4UUID.put(_object.getUUID(), _object);
// replace old cache with new values
// it is thread save because of volatile
setCache4Id(newCache4Id);
setCache4Name(newCache4Name);
setCache4UUID(newCache4UUID);
}
/**
* The method tests, if the cache has stored some entries.
*
* @return true if the cache has some entries, otherwise
* false
*/
public boolean hasEntries()
{
return (getCache4Id() != null && !getCache4Id().isEmpty())
|| (getCache4Name() != null && !getCache4Name().isEmpty())
|| (getCache4UUID() != null && !getCache4UUID().isEmpty());
}
/**
* The method initialize the cache.
*
* @param _initializer class name of the class initializing
*
*/
public void initialize(final Class _initializer)
{
this.initializer = _initializer.getName();
synchronized (this) {
try {
readCache();
} catch (final CacheReloadException e) {
AbstractCache.LOG.error("Unexpected error while initializing Cache for " + getClass(), e);
}
}
}
/**
* The complete cache is read and then replaces the current stored values
* in the cache. The cache must be read in this order:
*
* - create new cache map
* - read cache in the new cache map
* - replace old cache map with the new cache map
*
* This order is imported, otherwise
*
* - if the cache initialized first time, the cache is not
*
null and returns then wrong values
* - existing and read values could not be read while a reload is
* done
*
*
* @throws CacheReloadException if the cache could not be read (the
* exception is also written into the error
* log)
*/
private void readCache()
throws CacheReloadException
{
// if cache is not initialized, the correct order is required!
// otherwise the cache is not null and returns wrong values!
final Map newCache4Id = getNewCache4Id();
final Map newCache4Name = getNewCache4Name();
final Map newCache4UUID = getNewCache4UUID();
try {
readCache(newCache4Id, newCache4Name, newCache4UUID);
} catch (final CacheReloadException e) {
AbstractCache.LOG.error("Read Cache for " + getClass() + " failed", e);
throw e;
//CHECKSTYLE:OFF
} catch (final Exception e) {
//CHECKSTYLE:ON
AbstractCache.LOG.error("Unexpected error while reading Cache for " + getClass(), e);
throw new CacheReloadException("Unexpected error while reading Cache " + "for " + getClass(), e);
}
// replace old cache with new values
// it is thread save because of volatile
this.cache4Id = newCache4Id;
this.cache4Name = newCache4Name;
this.cache4UUID = newCache4UUID;
}
/**
* Method to fill this cache with objects.
*
* @param _newCache4Id cache for id
* @param _newCache4Name cache for name
* @param _newCache4UUID cache for UUID
* @throws CacheReloadException on error during reading
*/
protected abstract void readCache(final Map _newCache4Id,
final Map _newCache4Name,
final Map _newCache4UUID)
throws CacheReloadException;
/**
* Method to get a new empty Map for the id Cache.
* The method is implemented to provide the possibility to use
* different Map types in the extending classes.
*
* @return new empty Instance of a HashMap
*/
protected Map getNewCache4Id()
{
return new HashMap();
}
/**
* Method to get a new empty Map for the id Cache.
* The method is implemented to provide the possibility to use
* different Map types in the extending classes.
*
* @return new empty Instance of a HashMap
*/
protected Map getNewCache4Name()
{
return new HashMap();
}
/**
* Method to get a new empty Map for the id Cache.
* The method is implemented to provide the possibility to use
* different Map types in the extending classes.
*
* @return new empty Instance of a HashMap
*/
protected Map getNewCache4UUID()
{
return new HashMap();
}
/**
* Getter method for instance variable {@link #cache4Id}.
*
* @return value of instance variable {@link #cache4Id}
*/
public Map getCache4Id()
{
return this.cache4Id;
}
/**
* Setter method for instance variable {@link #cache4Id}.
*
* @param _cache4Id value for instance variable {@link #cache4Id}
*/
protected void setCache4Id(final Map _cache4Id)
{
this.cache4Id = _cache4Id;
}
/**
* Getter method for instance variable {@link #cache4Name}.
*
* @return value of instance variable {@link #cache4Name}
*/
protected Map getCache4Name()
{
return this.cache4Name;
}
/**
* Setter method for instance variable {@link #cache4Name}.
*
* @param _cache4Name value for instance variable {@link #cache4Name}
*/
protected void setCache4Name(final Map _cache4Name)
{
this.cache4Name = _cache4Name;
}
/**
* Setter method for instance variable {@link #cache4UUID}.
*
* @param _cache4uuid value for instance variable {@link #cache4UUID}
*/
protected void setCache4UUID(final Map _cache4uuid)
{
this.cache4UUID = _cache4uuid;
}
/**
* Getter method for instance variable {@link #cache4UUID}.
*
* @return value of instance variable {@link #cache4UUID}
*/
protected Map getCache4UUID()
{
return this.cache4UUID;
}
/**
* Getter method for instance variable {@link #initializer}.
*
* @return value of instance variable {@link #initializer}
*/
public String getInitializer()
{
return this.initializer;
}
/**
* Clear all values of this Cache.
*/
public void clear()
{
if (getCache4Id() != null) {
getCache4Id().clear();
}
if (getCache4Name() != null) {
getCache4Name().clear();
}
if (getCache4UUID() != null) {
getCache4UUID().clear();
}
}
/**
* The static method removes all values in all caches.
*/
public static void clearCaches()
{
synchronized (AbstractCache.CACHES) {
for (final AbstractCache cache : AbstractCache.CACHES) {
cache.getCache4Id().clear();
cache.getCache4Name().clear();
cache.getCache4UUID().clear();
}
}
}
/**
* Getter method for variable {@link #CACHES}.
*
* @return value of variable {@link #CACHES}
*/
public static Set> getCaches()
{
return AbstractCache.CACHES;
}
}