cache策略(三)基类

cache策略(三)基类
SimpleCache.java如下：
package com.sillycat.easyview.plugin.cache.base;

import com.sillycat.easyview.plugin.commons.exceptions.CacheException;

/**
* 一个最简单的CACHE的接口，适合只读型CACHE使用
*/
public interface SimpleCache {
Object get(Object key) throws CacheException;

void put(Object key, Object value) throws CacheException;
}

工具类Timestamper.java 这个类估计也是从hibernate的源码里面搞出来的
package com.sillycat.easyview.plugin.cache.base;

public class Timestamper {
private static short counter = 0;
private static long time;
private static final int BIN_DIGITS = 12;
public static final short ONE_MS = 1<<BIN_DIGITS;

public static long next() {
   synchronized(Timestamper.class) {
    long newTime = System.currentTimeMillis() << BIN_DIGITS;
    if (time<newTime) {
     time = newTime;
     counter = 0;
    }
    else if (counter < ONE_MS - 1 ) {
     counter++;
    }
  
    return time + counter;
   }
}

private Timestamper() {}
}


ReadOnlyCache.java如下：
package com.sillycat.easyview.plugin.cache.base;

import java.util.Comparator;

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

import com.sillycat.easyview.plugin.commons.exceptions.CacheException;

public class ReadOnlyCache implements BaseCache, SimpleCache {

private static final Log log = LogFactory.getLog(ReadOnlyCache.class);

private Cache cache;

public Object get(Object key, long txTimestamp) throws CacheException {
   Object result = cache.get(key);
   if (result != null && log.isDebugEnabled()) {
    log.debug("Cache hit: " + key);
   }
   return result;
}

public boolean put(Object key, Object value, long txTimestamp,
    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;
}

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

public void evict(Object key) throws CacheException {
}

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

public boolean insert(Object key, Object value) throws CacheException {
   return false;
}

public void release(Object key, SoftLock lock) throws CacheException {
   log.error("Application attempted to edit read only item: " + key);
}

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");
}

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;
}

public void remove(Object key) throws CacheException {
   cache.remove(key);
}

public void clear() throws CacheException {
   this.cache.clear();
}

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

public void setCache(Cache cache) {
   this.cache = cache;
}

public String getRegionName() {
   return cache.getRegionName();
}

public Cache getCache() {
   return this.cache;
}

public Object get(Object key) throws CacheException {
   return cache.get(key);
}

public void put(Object key, Object value) throws CacheException {
   cache.put(key, value);

}
}