如何在程序中加入缓存机制

看别人写的源程序，发现使用了缓存处理机制，好奇，学习了一下，很有意思的东西。

它使用的是whirlycache这一个开源项目，版本0.7.老了点。先用着。

//定义自己的缓存类

public class MemberCache {

//这里是默认的缓存时间

public static final long TIME_OUT = DateUtil.HOUR;

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

//创建一个单例

static private MemberCache instance = new MemberCache();

//真正的缓存对象，你缓存的东西全存在里面了

private Cache cache;

//构造函数

public MemberCache() {

try {

//初始化缓存对象

cache = CacheManager.getInstance().getCache("member");

} catch (CacheException ex) {

log.error("Cannot get the WhirlyCache. Member caching is disabled.", ex);

} catch (LinkageError e) {

// @todo: Should be never throw

log.error("Cannot get the WhirlyCache caused by Package Conflict. Member caching is disabled.", e);

}

}

static public MemberCache getInstance() {

return instance;

}

public String getEfficiencyReport() {

String result = "No report";

if (cache == null) {

if (MVNForumConfig.getEnableCacheMember() == false) {

result = "Cache is disabled.";

} else {

result = "Cache cannot be inited";

}

} else if (cache instanceof CacheDecorator) {

result = ((CacheDecorator)cache).getEfficiencyReport();

}

return result;

}

public void clear() {

if (cache != null) {

cache.clear();

}

}

//这里存储并读取缓存一个用户总数信息

public long getMemberTotalCount() throws ObjectNotFoundException, AssertionException, DatabaseException{

longcount = 0;

if (cache != null) {

//这里是键值

String key = new String("getMemberTotalCount");

//根据键值获取对象，这里原来是一个Long，但是存不进去，换成String就可以了

String Scount = (String)cache.retrieve(key);

//如果缓存中不存在

if (Scount == null) {

//从非缓存中读取

Scount= = String.valueOf(DAOFactory.getMemberDAO().getNumberOfMembers());

//存入缓存

cache.store(key, Scount, DateUtil.MINUTE);

log.info("缓存中不存在，创建后存入");

}else{

count=new Long(Scount);

log.info("从缓存中读取会员总数成功");

}

} else {

//当前缓存未启用，从数据库中直接读取

count = new Long(DAOFactory.getMemberDAO().getNumberOfMembers());

}

}

}

很简单吧。