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Hello to all,

I plan to store a reference key to an other cache value in an object value.
I'm wondering if it is possible to check the reference key existence into an EhCache Query.

The idea :
Code:

key1   => Element{key2}
 key2 => Element{...}
 
 Element key1 refers to element k2 by a value argument.

Attribute<Integer> key = cache.getSearchAttribute("key");
query.addCriteria(new IsKeyExist(key);

It is possible to do this kind of thing with the EhCache search API ?

I'm not sure I understand your question exactly, perhaps with some code a little more fleshed out I might get a better idea.

The easiest way to tell if a key exists in a cache is just call get()

Teck, my goal is to test the existence of a key contains in a value attribute in a search query execution.

I think is not possible. By the way, I put some code to explain my need:

I have an object A with a variable named "pointerToB". "pointerToB" is a pointer to an other value in the cache; this parameter contains the cached element key of the pointed value.

Code:

class A{
   String pointerToB;
 }
 
 A a = new A();
 A b = new A();
 String keyOfA=...;
 String keyOfB=...;
 
 a.setPointerToB(keyOfB);
 
  
 cache.put(new Element(keyOfA, a));
 cache.put(new Element(keyOfB, b));

Now, I want to find all A objects that reference an existing B objet; B objects can be evicted of the cache and not existing anymore in the cache.

To do that job, ideally, I need a new search attribute method's that I named below "keyExist()".

Code:

Query query = cache.createQuery();
 Attribute<String> pointerToBAttribute = cache.getSearchAttribute("pointerToB");
 query.addCriteria(pointerToBAttribute.keyExist());
 query.execute();

It is possible to do this thing in EhCache ?

I think the only way to accomplish that at the moment is to select all values for the "pointerToB" attribute and execute get() calls yourself.

Thanks teck.

Now, I finally update "pointerToB" value to null on every B object deletion.
So, I check if this attribute is not null in my search expression.

Sorry was that a question in your last post about "not-null" in your search expression?

Search in ehcache doesn't have a concept of a null value for attributes at the moment. There is no [direct] way to search for elements which have null for a given attribute. The best you can do at the moment is to use a boolean attribute for this purpose. Adding proper support for nulls is on the roadmap though

I created a custom AttributeExtractor (that returns a Boolean value) to test if this parameter is null.