using same Element instance in multiple cache

This question might be a bit silly or pedantic, but is it strictly wrong to put() the same Element instance in more than one cache? The element instance itself doesn’t look like it has a back reference to the containing cache, so that aspect seems okay.

 

Anyway, just wondering if anyone has thoughts on this? Apologies if I’ve missed a prior post/FAQ/javadoc/etc on this – I did search.

 

thanks

-tim

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Thanks Greg! To give you a little context to this question….I think someone here at Terracotta made a bad assumption that Elements wouldn’t be used in more than one Cache (we inject a back reference to the cache which simply isn’t a valid thing to do). I’ll see that it is resolved.

 

Any idea how common this type of usage is in the wild (ie. using the same Element in more than one cache)?

 

-tim

 

 

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From: Greg Luck [gluck@...] 
Sent: Tuesday, May 20, 2008 3:26 PM
To: Tim Eck
Cc: ehcache-list@...
Subject: Re: [ehcache-list] using same Element instance in multiple cache

 

Tim

 

No it is not incorrect. There are no back references. 

 

If you put an Element in a Cache, it means the Cache holds a reference to it, or if it is serialzed to disk, a file pointer.

 

When you retrieve an element from a cache, most of the time you will have a local variable or something else which will hold a reference to it, until it goes out of scope. That is normal operation. 

 

To remove an Element from a Cache with in an MemoryStore really means to remove the reference. The Element continues to exist until it gets Garbage collected. If it is in another Cache, then it will not be and you can still use it. 

 

The only real complication comes with DiskStore. Once an Element gets Serialized and then you get it and it gets Deseriazilzed it will be a different Object graph to the one you are holding onto in the other Cache. As long as you realise this, no problem.

 

 

On 21/05/2008, at 7:12 AM, Tim Eck wrote:

This question might be a bit silly or pedantic, but is it strictly wrong to put() the same Element instance in more than one cache? The element instance itself doesn’t look like it has a back reference to the containing cache, so that aspect seems okay.

 

Anyway, just wondering if anyone has thoughts on this? Apologies if I’ve missed a prior post/FAQ/javadoc/etc on this – I did search.

 

thanks

-tim

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Regards

 

Greg Luck

 

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