One persistent problem with the current Entity Engine implementation is
the use of ThreadLocal variables in the Delegator and Transactions.
Their use makes it difficult (and sometimes impossible) to fix Entity
Engine bugs. They also make it impossible to multi-thread a Delegator
instance.
Here is what I have had percolating in my head the last few months:
Transaction tx = TransactionFactory.newTransaction();
Delegator delegator = tx.getDelegator("default");
// Do stuff with delegator
Transaction nestedTx = TransactionFactory.newTransaction();
Delegator nestedDelegator = nestedTx.getDelegator("default");
// Do stuff with nestedDelegator
nestedTx.commit();
tx.commit();
A Delegator instance always references the transaction it is running in.
The advantage to this approach is we gain the ability to hand off
Delegator instances to other threads. Other threads can even
commit/rollback a transaction:
Transaction tx = delegator.getTransaction();
tx.commit();
After a commit, the Delegator instance is discarded. Any attempt to use
it after a commit throws an exception (the same is true with the
Transaction instance).
Another problem is Delegator localization - which also uses ThreadLocal
variables. We can localize Delegator instances like this:
Transaction tx = TransactionFactory.newTransaction();
Delegator delegator = tx.getDelegator("default", locale);
Finally, the current implementation has a caching problem:
https://issues.apache.org/jira/browse/OFBIZ-5534
With the new design, the Delegator instance, Transaction instance, and
entity cache are tightly coupled - so that problem is easy to solve.
What do you think?
--
Adrian Crum
Sandglass Software
www.sandglass-software.com
