[jbosscache-dev] Need for CacheLoader.storeState?

[Vladimir Blagojevic]

Hey,

There is an interesting quirk with this whole thing. In brief,
storeState implementation of AbstractCacheLoader after it reads NodeData
from inputstream it writes it to cache like this:

if (nd.attrs != null)
	put(fqn, nd.attrs, true);  //void put(Fqn name, Map
attributes,boolean erase) throws Exception;
else
       put(fqn, null); // void put(Fqn name, Map attributes) throws
Exception;

As you know true parameter in put clears the existing map. However,the
trick is that CacheLoader only exposes:

void put(Fqn name, Map attributes) throws Exception; 

and not 

void put(Fqn name, Map attributes,boolean erase) throws Exception;

So I cannot move storeState up to AbstractCacheLoader unless we expose
put with erase.


It took me like two hours to figure this out since compiler did not
complain - it automatically boxed boolean parameter and linked
invocation of put(fqn, nd.attrs, true); to method Object put(Fqn name,
Object key, Object value) throws Exception;

I did a very simple change of moving storeState to AbstractCacheLoader
and tests started to fail. I thought I was halucinating. 

So what do we do? 


> -----Original Message-----
> From: Bela Ban 
> Sent: Thursday, August 31, 2006 5:47 PM
> To: Vladimir Blagojevic
> Cc: jbosscache-dev at lists.jboss.org
> Subject: Re: [jbosscache-dev] Need for CacheLoader.storeState?
> 
> Absolutely, I had that idea when I wrote the cache loader 
> interface, but never saw it through... +1 for sure, this 
> takes a lot of pain out of the implementations.
> 
> Are you guys thinking about a more efficient transfer format, 
> or is NodeData still the awy to go ?
> 
> Vladimir Blagojevic wrote:
> > Hi,
> >
> > After we resolve streaming format incompatible cacheloader 
> > implementations [1][2], and as we continue to follow newly agreed 
> > streaming state transfer format - we do not have to require 
> > cacheloader implementers to write their own implementations of 
> > storeEntireState and storeState !
> >
> > CacheLoader.storeEntireState and CacheLoader.storeState are 
> always the 
> > same. They read NodeData objects from stream and call put with 
> > underlying cacheloader. Put method does the cacheloader 
> specific stuff.
> >
> > We can possibly keep storeEntireState and storeState in CacheLoader 
> > API but move default implementations to AbstractCacheLoader. Any 
> > suggestions or opinions?
> >
> >
> > [1] http://jira.jboss.com/jira/browse/JBCACHE-748
> > [2] http://jira.jboss.com/jira/browse/JBCACHE-749
> >
> > _______________________________________________
> > jbosscache-dev mailing list
> > jbosscache-dev at lists.jboss.org
> > https://lists.jboss.org/mailman/listinfo/jbosscache-dev
> >
> >   
> 
> --
> Bela Ban
> Lead JGroups / Manager JBoss Clustering Group JBoss - a 
> division of Red Hat
> 
>