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 

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.

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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:

1. the idle time is non-zero and has elapsed, unless the cache is eternal; or
2. the time to live is non-zero and has elapsed, unless the cache is eternal; or
3. 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

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示例代码：

Element element=cache.getQuiet(key);
        log.info("element:"+element);
        if(element!=null){
            log.info("cache.isExpired(element):"+cache.isExpired(element));
            log.info("cacheName:" + cacheName + " key:" + key + " isExist:true");
            return true;
        }
        else{
            log.info("cacheName:" + cacheName + " key:" + key + " isExist:false");
            return false;
        }