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//$Id: ReadOnlyCache.java 9247 2006-02-09 20:48:43Z steveebersole $
package org.hibernate.cache;

import java.util.Comparator;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

/**
 * Caches data that is never updated.
 * @see CacheConcurrencyStrategy
 */
public class ReadOnlyCache implements CacheConcurrencyStrategy {
	
	private Cache cache;
	private static final Log log = LogFactory.getLog(ReadOnlyCache.class);
	
	public ReadOnlyCache() {}
	
	public void setCache(Cache cache) {
		this.cache=cache;
	}

	public Cache getCache() {
		return cache;
	}

	public String getRegionName() {
		return cache.getRegionName();
	}
	
	public synchronized Object get(Object key, long timestamp) throws CacheException {
		Object result = cache.get(key);
		if ( result!=null && log.isDebugEnabled() ) log.debug("Cache hit: " + key);
		return result;
	}
	
	/**
	 * Unsupported!
	 */
	public SoftLock lock(Object key, Object version) {
		log.error("Application attempted to edit read only item: " + key);
		throw new UnsupportedOperationException("Can't write to a readonly object");
	}
	
	public synchronized boolean put(
			Object key, 
			Object value, 
			long timestamp, 
			Object version, 
			Comparator versionComparator,
			boolean minimalPut) 
	throws CacheException {
		if ( minimalPut && cache.get(key)!=null ) {
			if ( log.isDebugEnabled() ) log.debug("item already cached: " + key);
			return false;
		}
		if ( log.isDebugEnabled() ) log.debug("Caching: " + key);
		cache.put(key, value);
		return true;
	}
	
	/**
	 * Unsupported!
	 */
	public void release(Object key, SoftLock lock) {
		log.error("Application attempted to edit read only item: " + key);
		//throw new UnsupportedOperationException("Can't write to a readonly object");
	}
	
	public void clear() throws CacheException {
		cache.clear();
	}

	public void remove(Object key) throws CacheException {
		cache.remove(key);
	}
	
	public void destroy() {
		try {
			cache.destroy();
		}
		catch (Exception e) {
			log.warn("could not destroy cache", e);
		}
	}

	/**
	 * Unsupported!
	 */
	public boolean afterUpdate(Object key, Object value, Object version, SoftLock lock) throws CacheException {
		log.error("Application attempted to edit read only item: " + key);
		throw new UnsupportedOperationException("Can't write to a readonly object");
	}

	/**
	 * Do nothing.
	 */
	public boolean afterInsert(Object key, Object value, Object version) throws CacheException {		
		if ( log.isDebugEnabled() ) log.debug("Caching after insert: " + key);
		cache.update(key, value);
		return true;
	}

	/**
	 * Do nothing.
	 */
	public void evict(Object key) throws CacheException {
		// noop
	}

	/**
	 * Do nothing.
	 */
	public boolean insert(Object key, Object value, Object currentVersion) {
		return false;
	}

	/**
	 * Unsupported!
	 */
	public boolean update(Object key, Object value, Object currentVersion, Object previousVersion) {
		log.error("Application attempted to edit read only item: " + key);
		throw new UnsupportedOperationException("Can't write to a readonly object");
	}

	public String toString() {
		return cache + "(read-only)";
	}

}