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From Dan Connelly <>
Subject Re: ManageableCollectionUtil should not throw "unsupported" JcrMapping exception.
Date Sun, 03 Sep 2006 22:11:28 GMT
What I ended up doing for this problem, to avoid the exception, was to 
make a local modification in ManageableCollectionUtil.    It still 
throws the exception (if needed) but my specialized list collection 
class is now easily coerced to a ManageableCollection with my 
replacement code.

This is a hack, but a much smaller hack than trying to specialize either 
the objectConverter or the collectionConverter to do the wrapping.

I would like to see the CollectionConverter interface extended with a 
 private  ManageableCollectionFactory  getManageableCollectionFactory()
 such that the ManageableCollectionFactory class would be used in much 
the same way that ManageableCollectionUtil is ued.

The ManageableCollectionFactory would continue to throw the 
"unsupported" JcrMapping exception (if needed), but presumably would 
wrap all of the application's collection classes correctly.

Dan Connelly wrote:

> I want to use a custom collectionConverter, MyCollectionConverterImpl.
> That collectionConverter can decide what to do with "unsupported" 
> collections from my *given* object model.   (Object model cannot be 
> changed.)    In particular, MyCollectionConverterImpl will wrap  an 
> unsupported collection as a ManageableCollection and delegate its work 
> to a standard collection converter. 
> The collection type is discovered by reflection in the 
> objectConverter, so it cannot be coerced in the ocm mapping.
> Unfortunately, the default objectConverter invokes its own wrapping 
> tool, ManageableCollectionUtil, just before the call to 
> insertCollection in the custom collectionConverter.     
> ManageableCollectionUtil will throw an exception before the custom 
> collectionConverter gets its chance to wrap the unsupported collection 
> type.     The call to insertCollection in the custom 
> collectionConverter is never invoked.
> A workaround would be to over-ride method insertCollectionFields using 
> a custom objectConverter.   However, this method  is private in the 
> standard objectConverter.  Thus the method work cannot be delegated.   
> Code would need to be copied into the custom objectConverter.   Not 
> good.   But even if this method was public and code copying was not 
> needed, the object converter is not the right place for collection 
> conversions.
> Why not make the collectionConverters responsible for throwing an 
> exception on (truly) unsupported collection types? 
> Don't throw this exception from ManageableCollectionUtil.   Just leave 
> an "unsupported" collection type alone there and let the 
> collectionConverter deal with any unsupported collection type that may 
> be given to it.
>       -- Dan

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