package org.apache.commons.jcs.access;
/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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.
*/
import java.io.IOException;
import java.util.HashMap;
import java.util.Map;
import java.util.Set;
import org.apache.commons.jcs.access.behavior.ICacheAccess;
import org.apache.commons.jcs.access.exception.CacheException;
import org.apache.commons.jcs.access.exception.InvalidArgumentException;
import org.apache.commons.jcs.access.exception.InvalidHandleException;
import org.apache.commons.jcs.access.exception.ObjectExistsException;
import org.apache.commons.jcs.engine.CacheElement;
import org.apache.commons.jcs.engine.behavior.ICacheElement;
import org.apache.commons.jcs.engine.behavior.IElementAttributes;
import org.apache.commons.jcs.engine.control.CompositeCache;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
/**
* This class provides an interface for all types of access to the cache.
* <p>
* An instance of this class is tied to a specific cache region. Static methods are provided to get
* such instances.
* <p>
* Using this class you can retrieve an item, the item's wrapper, and the element's configuration. You can also put an
* item in the cache, remove an item, and clear a region.
* <p>
* The JCS class is the preferred way to access these methods.
*/
public class CacheAccess<K, V>
extends AbstractCacheAccess<K, V>
implements ICacheAccess<K, V>
{
/** The logger. */
private static final Log log = LogFactory.getLog( CacheAccess.class );
/**
* Constructor for the CacheAccess object.
* <p>
* @param cacheControl The cache which the created instance accesses
*/
public CacheAccess( CompositeCache<K, V> cacheControl )
{
super(cacheControl);
}
/**
* Retrieve an object from the cache region this instance provides access to.
* <p>
* @param name Key the object is stored as
* @return The object if found or null
*/
@Override
public V get( K name )
{
ICacheElement<K, V> element = this.getCacheControl().get( name );
return ( element != null ) ? element.getVal() : null;
}
/**
* Retrieve matching objects from the cache region this instance provides access to.
* <p>
* @param pattern - a key pattern for the objects stored
* @return A map of key to values. These are stripped from the wrapper.
*/
@Override
public Map<K, V> getMatching( String pattern )
{
HashMap<K, V> unwrappedResults = new HashMap<K, V>();
Map<K, ICacheElement<K, V>> wrappedResults = this.getCacheControl().getMatching( pattern );
if ( wrappedResults != null )
{
for (Map.Entry<K, ICacheElement<K, V>> entry : wrappedResults.entrySet())
{
ICacheElement<K, V> element = entry.getValue();
if ( element != null )
{
unwrappedResults.put( entry.getKey(), element.getVal() );
}
}
}
return unwrappedResults;
}
/**
* This method returns the ICacheElement<K, V> wrapper which provides access to element info and other
* attributes.
* <p>
* This returns a reference to the wrapper. Any modifications will be reflected in the cache. No
* defensive copy is made.
* <p>
* This method is most useful if you want to determine things such as the how long the element
* has been in the cache.
* <p>
* The last access time in the ElementAttributes should be current.
* <p>
* @param name Key the Serializable is stored as
* @return The ICacheElement<K, V> if the object is found or null
*/
@Override
public ICacheElement<K, V> getCacheElement( K name )
{
return this.getCacheControl().get( name );
}
/**
* Get multiple elements from the cache based on a set of cache keys.
* <p>
* This method returns the ICacheElement<K, V> wrapper which provides access to element info and other
* attributes.
* <p>
* This returns a reference to the wrapper. Any modifications will be reflected in the cache. No
* defensive copy is made.
* <p>
* This method is most useful if you want to determine things such as the how long the element
* has been in the cache.
* <p>
* The last access time in the ElementAttributes should be current.
* <p>
* @param names set of Serializable cache keys
* @return a map of K key to ICacheElement<K, V> element, or empty map if none of the keys are present
*/
@Override
public Map<K, ICacheElement<K, V>> getCacheElements( Set<K> names )
{
return this.getCacheControl().getMultiple( names );
}
/**
* Get multiple elements from the cache based on a set of cache keys.
* <p>
* This method returns the ICacheElement<K, V> wrapper which provides access to element info and other
* attributes.
* <p>
* This returns a reference to the wrapper. Any modifications will be reflected in the cache. No
* defensive copy is made.
* <p>
* This method is most useful if you want to determine things such as the how long the element
* has been in the cache.
* <p>
* The last access time in the ElementAttributes should be current.
* <p>
* @param pattern key search pattern
* @return a map of K key to ICacheElement<K, V> element, or empty map if no keys match the pattern
*/
@Override
public Map<K, ICacheElement<K, V>> getMatchingCacheElements( String pattern )
{
return this.getCacheControl().getMatching( pattern );
}
/**
* Place a new object in the cache, associated with key name. If there is currently an object
* associated with name in the region an ObjectExistsException is thrown. Names are scoped to a
* region so they must be unique within the region they are placed.
* <p>
* @param key Key object will be stored with
* @param value Object to store
* @throws CacheException and ObjectExistsException is thrown if the item is already in the
* cache.
*/
@Override
public void putSafe( K key, V value )
{
if ( this.getCacheControl().get( key ) != null )
{
throw new ObjectExistsException( "putSafe failed. Object exists in the cache for key [" + key
+ "]. Remove first or use a non-safe put to override the value." );
}
put( key, value );
}
/**
* Place a new object in the cache, associated with key name. If there is currently an object
* associated with name in the region it is replaced. Names are scoped to a region so they must
* be unique within the region they are placed.
* @param name Key object will be stored with
* @param obj Object to store
*/
@Override
public void put( K name, V obj )
{
// Call put with a copy of the contained caches default attributes.
// the attributes are copied by the cacheControl
put( name, obj, this.getCacheControl().getElementAttributes() );
}
/**
* Constructs a cache element with these attributes, and puts it into the cache.
* <p>
* If the key or the value is null, and InvalidArgumentException is thrown.
* <p>
* @see org.apache.commons.jcs.access.behavior.ICacheAccess#put(Object, Object, IElementAttributes)
*/
@Override
public void put( K key, V val, IElementAttributes attr )
{
if ( key == null )
{
throw new InvalidArgumentException( "Key must not be null" );
}
if ( val == null )
{
throw new InvalidArgumentException( "Value must not be null" );
}
// Create the element and update. This may throw an IOException which
// should be wrapped by cache access.
try
{
CacheElement<K, V> ce = new CacheElement<K, V>( this.getCacheControl().getCacheName(), key,
val );
ce.setElementAttributes( attr );
this.getCacheControl().update( ce );
}
catch ( IOException e )
{
throw new CacheException( e );
}
}
/**
* Removes a single item by name.
* <p>
* @param name the name of the item to remove.
*/
@Override
public void remove( K name )
{
this.getCacheControl().remove( name );
}
/**
* Reset attributes for a particular element in the cache. NOTE: this method is currently not
* implemented.
* <p>
* @param name Key of object to reset attributes for
* @param attr New attributes for the object
* @throws InvalidHandleException if the item does not exist.
*/
@Override
public void resetElementAttributes( K name, IElementAttributes attr )
{
ICacheElement<K, V> element = this.getCacheControl().get( name );
if ( element == null )
{
throw new InvalidHandleException( "Object for name [" + name + "] is not in the cache" );
}
// Although it will work currently, don't assume pass by reference here,
// i.e. don't do this:
// element.setElementAttributes( attr );
// Another reason to call put is to force the changes to be distributed.
put( element.getKey(), element.getVal(), attr );
}
/**
* GetElementAttributes will return an attribute object describing the current attributes
* associated with the object name. The name object must override the Object.equals and
* Object.hashCode methods.
* <p>
* @param name Key of object to get attributes for
* @return Attributes for the object, null if object not in cache
*/
@Override
public IElementAttributes getElementAttributes( K name )
{
IElementAttributes attr = null;
try
{
attr = this.getCacheControl().getElementAttributes( name );
}
catch ( IOException ioe )
{
log.error( "Failure getting element attributes", ioe );
}
return attr;
}
}