ehcache如何判断缓存数据是否存在--isKeyInCache

Posted on 2011-04-22 15:59 asdtiang 阅读(5552) 评论(0) 编辑收藏 ehcache如何判断缓存数据是否存在--isKeyInCache

boolean isKeyInCache(java.lang.Object key)

An inexpensive check to see if the key exists in the cache.

Parameters:: key - the key to check for
Returns:: true if an Element matching the key is found in the cache. No assertions are made about the state of the Element.

这个方法是Ehcache的方法，它只判断key是否存在，并不判断这个缓存元素过期没有，所以当元素加入缓存时key就一直存在，所以就算元素过期，只要key被缓存过一次，这个方法就返回true,
即缓存元素被移除的话，key还存在。

程序就不能用这个方法来判断缓存中是否存在这个某个缓存元素。
得用如下方法：

getQuiet

Element getQuiet(java.lang.Object key)
throws java.lang.IllegalStateException,
CacheException

Gets an element from the cache, without updating Element statistics. Cache statistics are also not updated.

Parameters:: key - a serializable value
Returns:: the element, or null, if it does not exist.
Throws:: java.lang.IllegalStateException - if the cache is not Status.STATUS_ALIVE; CacheException
Since:: 1.2
See Also:: isExpired(net.sf.ehcache.Element)

isExpired

boolean isExpired(Element element)
throws java.lang.IllegalStateException,
java.lang.NullPointerException

Checks whether this cache element has expired.

The element is expired if:

the idle time is non-zero and has elapsed, unless the cache is eternal; or
the time to live is non-zero and has elapsed, unless the cache is eternal; or
the value of the element is null.

Parameters:: element - the element to check
Returns:: true if it has expired
Throws:: java.lang.IllegalStateException - if the cache is not Status.STATUS_ALIVE; java.lang.NullPointerException - if the element is null

示例代码：

Element element=cache.getQuiet(key);
ehcache如何判断缓存数据是否存在--isKeyInCache

log.info("element:"+element);
}