Currently there is the TransactionContext with static accessors for the current thread's TransactionContext and a TransactionContextManager object/gbean with non-static accessors and helper methods to create the various types of TC and associate them with the current thread. Some components use the TransactionContext static methods and some use the gbean methods.
We have a problem that new threads don't automatically get a TC. For threads we create, we can add code to create the TC, but for threads created e.g. by a servlet we have no direct access to do so.
Our TC cannot safely be shared between threads. Therefore I don't think that using an InheritableThreadLocal in TC is a good solution.
My proposal, which I will implement in the absence of other suggestions, is to eliminate the static methods on TC and just use the gbean accessors. The getTransactionContext method will never return null: if there is no TC for the current thread it will create a new UnspecifiedTransactionContext and associate it with the thread before returning. I may create an additional method for this, getNonNullTransactionContext, so the existing method can be used where it would be an error for no TransactionContext to be associated with the current thread.
The advantage I see in using a gbean rather that static methods is that is will simplify plugging in a different set of TransactionContext implementations should we wish to do so.