java动态缓存技术：WEB缓存应用

　　可以实现不等待，线程自动更新缓存

　　java动态缓jar包http://dl2.csdn.net/down4/20070918/18203740920.jar

　　源代码：

　　CacheData.java 存放缓存数据的Bean

/** *//**
*
*/
package com.cari.web.cache;

/** *//**
* @author zsy
*
*/
public class CacheData ...{
private Object data;
private long time;
private int count;

public CacheData() ...{

}

public CacheData(Object data, long time, int count) ...{
this.data = data;
this.time = time;
this.count = count;
}

public CacheData(Object data) ...{
this.data = data;
this.time = System.currentTimeMillis();
this.count = 1;
}

public void addCount() ...{
count++;
}

public int getCount() ...{
return count;
}
public void setCount(int count) ...{
this.count = count;
}
public Object getData() ...{
return data;
}
public void setData(Object data) ...{
this.data = data;
}
public long getTime() ...{
return time;
}
public void setTime(long time) ...{
this.time = time;
}
}

CacheOperation.java 缓存处理类

package com.cari.web.cache;

import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Hashtable;

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

/** *//**
* @author zsy
*/
public class CacheOperation ...{
private static final Log log = LogFactory.getLog(CacheOperation.class);
private static CacheOperation singleton = null;

private Hashtable cacheMap; //存放缓存数据

private ArrayList threadKeys; //处于线程更新中的key值列表

public static CacheOperation getInstance() ...{
if (singleton == null) ...{
singleton = new CacheOperation();
}
return singleton;
}

private CacheOperation() ...{
cacheMap = new Hashtable();
threadKeys = new ArrayList();
}

/** *//**
* 添加数据缓存
* 与方法getCacheData(String key, long intervalTime, int maxVisitCount)配合使用
* @param key
* @param data
*/
public void addCacheData(String key, Object data) ...{
addCacheData(key, data, true);
}

private void addCacheData(String key, Object data, boolean check) ...{
if (Runtime.getRuntime().freeMemory() ＜ 5L*1024L*1024L) ...{//虚拟机内存小于10兆，则清除缓存
log.warn("WEB缓存：内存不足，开始清空缓存！");
removeAllCacheData();
return;
} else if(check && cacheMap.containsKey(key)) ...{
log.warn("WEB缓存：key值= " + key + " 在缓存中重复, 本次不缓存！");
return;
}
cacheMap.put(key, new CacheData(data));
}

/** *//**
* 取得缓存中的数据
* 与方法addCacheData(String key, Object data)配合使用
* @param key
* @param intervalTime 缓存的时间周期，小于等于0时不限制
* @param maxVisitCount 访问累积次数，小于等于0时不限制
* @return
*/
public Object getCacheData(String key, long intervalTime, int maxVisitCount) ...{
CacheData cacheData = (CacheData)cacheMap.get(key);
if (cacheData == null) ...{
return null;
}
if (intervalTime ＞ 0 && (System.currentTimeMillis() - cacheData.getTime()) ＞ intervalTime) ...{
removeCacheData(key);
return null;
}
if (maxVisitCount ＞ 0 && (maxVisitCount - cacheData.getCount()) ＜= 0) ...{
removeCacheData(key);
return null;
} else ...{
cacheData.addCount();
}
return cacheData.getData();
}

/** *//**
* 当缓存中数据失效时，用不给定的方法线程更新数据
* @param o 取得数据的对像(该方法是静态方法是不用实例，则传Class实列)
* @param methodName 该对像中的方法
* @param parameters 该方法的参数列表(参数列表中对像都要实现toString方法,若列表中某一参数为空则传它所属类的Class)