Add Datastore Cache Impl. [moved]

[jyemin]

This is Issue 25 moved from a Google Code project.
Added by 2010-04-02T18:51:03.000Z by scotthernandez.
Please review that bug for more context and additional comments, but update this bug.

Original labels: Type-Enhancement, Priority-Low, Milestone-Release1.2

Original description

Add a write-through datastore cache. This will cache entities loaded/saved by 
the instance of the datastore, via a instance hashmap. Adding this enables 
the datastore to effectively cache simple get(MyEntity.class, id) calls and 
get(MyEntity.class, ids). All writes will pass through the cache and update 
it once completed.

This will be similar to the JPA (lst level) session cache.

This can be written as CachingDatastoreImpl which can be substituted in the 
DatastoreService.getDatastore(true), or something like that.