[CAY-1778] TransactionManager to simplify user-managed transactions

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 3.2.M1
• Assignee: Andrus Adamchik
• Reporter: Andrus Adamchik
• Created: 06/Dec/12 11:53
• Updated: 06/Dec/12 12:07
• Resolved: 06/Dec/12 12:07

Description

Getting the semantics of manual transactions right is really hard: http://cayenne.apache.org/docs/3.0/understanding-transactions.html We need something more straightforward and DI based. Proposing the following:

public interface TransactionManager {

/**

• Starts a new transaction (or joins an existing one) calling
• {@link TransactionalOperation#perform(CayenneRuntime)}

  , and then

• committing or rolling back the transaction. Frees the user
  */
  <T> T performInTransaction(TransactionalOperation<T> op);
  }

public interface TransactionalOperation<T> {

/**

• A callback method that {@link TransactionManager} invokes,
  * {@link TransactionManager}

  will wrap this method call in a single

• thread-bound transaction.
  */
  T perform(CayenneRuntime runtime);
  }

So a custom block of code to run in TX may look like this:

runtime.getTransactionManager().performInTransaction(new TransactionalOperation<SomeType>() {
SomeType perform(CayenneRuntime runtime)

{ // do something }
});

or maybe even:

runtime.performInTransaction(new TransactionalOperation<SomeType>() {
SomeType perform(CayenneRuntime runtime) { // do something }

});

Later we may even use TransactionManager API for internal tx's to achieve uniformity. I can also see the evolution of the current Transaction API (including static bind methods) to gradually move under TransactionManager methods.