[Simple-support] Creating a "short" serialization

[Ben W. <si...@be...>]

We have several places in our code where we could benefit from a shorter 
serialization.  We don't need to serialize the entire object, just the 
primary keys of the object.

I haven't been able to find a way to do this yet.  Did I miss something? 
Is there a way to do it currently?

My thoughts on how to implement it:

The primary key attributes/elements would need to be annotated.  The 
most general way to do it would be to add a String "tag" option to the 
"Attribute" and "Element" annotations.  The tag would be a string that 
groups certain attributes together and can be used later.
I don't know why it would be necessary right now, but we could have any 
number of "sets of serializations" with any named tag we want: A "Short" 
one that would (de)derialize to just the primary keys, a "medium" one 
that would (de)serialize to only certain attributes, and then the 
default that would work normally using all annotations (as it does now).

1) It could be done with a custom Strategy, but alas, "Strategy"s are 
only notified about elements (via setElement(...)).  If there were a 
setAttribute(...) method that was called on strategies, the custom 
strategy could look up the Object's annoations, find the right ones, and 
only let certain attributes and elements be written out to the DOM. 
This has the benefit of the least about of core simpleframework code 
changes.

2) The Source object could have a "List<String> tags" object that holds 
the current tags to serialize on.  The Source can tell the scanner what 
tags to look for.  Only the matching tags are included as attributes and 
elements for objects.  The Persister/Serializer will need to have a 
setTags() method that it can pass on to the Source.
The downside of this approach is that more code would have to be 
changed. The benefit is that not all of the attributes/elements would be 
looped over unnecessarily if there is only a "short" serialization going on.

I am happy to code this up and submit a patch.  However, I am not sure 
which you would prefer.  There might be a third option that I'm missing. 
  Please point me in the right direction if that is the case.

Thanks,
Ben