Class Transactions
The transaction a @Transactional method runs in, bound to the calling
thread.
The build rewrites every @Transactional method into a call to
begin(int, boolean, int), the original body, then commit(Transactions.Transaction) -- or
afterThrow(Transactions.Transaction, boolean) with the rollback decision it worked out from the
annotation. The propagation, the read-only flag and the timeout arrive as
constants, so this class interprets nothing: it holds the one piece of state
that has to exist at run time, which is which connection the thread's
transaction is on.
Joining
Nothing has to be handed the transaction. DataSource.borrow() asks this
class first, and a thread inside a transaction gets the transaction's
connection back instead of a pooled one -- so the pool's own methods, an
EntityManager's daos and a managed session all join it. The connection
is borrowed, and BEGIN sent, only when the transaction first needs it: a
@Transactional method that returns before touching the database costs
a thread-local write and nothing else.
A thread that has never begun a transaction does not even read the
thread-local: used is set by the first begin(int, boolean, int) of the process,
on the thread that is then inside it, so every other thread reading a stale
false is correct -- none of them is in a transaction.
Propagation
Spring's seven, one for one; the constants below are the ordinals of
com.codename1.backend.annotations.Propagation. A method that joins a
transaction and fails with a rollback-worthy exception marks the whole
transaction rollback-only, and the method that began it then rolls back and
throws TransactionException.UnexpectedRollback rather than reporting
a commit that did not happen.
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Method Summary
Modifier and TypeMethodDescriptionstatic booleanisActive()Whether the calling thread is inside a transaction.static booleanWhether the calling thread's transaction has been marked rollback-only.static voidMarks the calling thread's transaction so it rolls back however its method ends -- the programmatic form of throwing, for a method that wants to return a value and still undo its work.
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Method Details
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isActive
public static boolean isActive()Whether the calling thread is inside a transaction. -
isRollbackOnly
public static boolean isRollbackOnly()Whether the calling thread's transaction has been marked rollback-only. -
setRollbackOnly
public static void setRollbackOnly()Marks the calling thread's transaction so it rolls back however its method ends -- the programmatic form of throwing, for a method that wants to return a value and still undo its work.
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