If your class is simply a wrapper or a data structure, then there is no much overhead( less than 100 bytes) to make it a object instance. But how to manage resource efficiently and object's lifecycle can be complicated. i.e.: no matter you store it in a dedicate cache or session, how to control memory size, when to expire it if it becomes obsolete due to update or delete...In general, you need a mechanism that can selective cache any table( cache from Expresso is a good ref), with basic control ( LRU or usage count), at least use a weak referenced hashmap to avoid overload. If the cached info is not read only, you'd better make it a class, it's smart enough to sync itself with DB and cache when change happens.
