ehcache如何判斷緩存數據是否存在--isKeyInCache

 

Posted on 2011-04-22 15:59  asdtiang 閱讀(5552)  評論(0)   編輯   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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這個方法是Ehcache的方法，它只判斷key是否存在，並不判斷這個緩存元素過期沒有，所以當元素加入緩存時key就一直存在，所以就算元素過期，只要key被緩存過一次，這個方法就返回true,
即緩存元素被移除的話，key還存在。


程序就不能用這個方法來判斷緩存中是否存在這個某個緩存元素。
 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)

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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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示例代碼：

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;
        }