easyutils

A collection of utility classes.

Transactional

Think of java.util.Optional and transactional procedures. A sequence of interconnected operations can be performed in a transactional context without explicitly dealing with transactions.

Here's a contrived example. recordTransaction returns a Transactional wrapping a procedure for adding (or subtracting) amounts to the balance of the given account in context of Ctx transaction context. transferFunds utilises Transactional::flatMap to chain the operations. When Transactional::get is called at the end of the chain, the two procedures are performed in a transaction scope and the result of the last procedure is returned.

/**
 * A method for adding monetary transactions to a log.
 */
Transactional<Account, Ctx> recordTransaction(UUID accountId, BigDecimal amount);

/**
 * Transfer funds from one account to another transactionally.
 */
void transferFunds(UUID from, UUID to, BigDecimal amount) {
    recordTransaction(from, amount.negate())
        .flatMap(ignore -> recordTransaction(to, amount))
        .get();
}

The ignore parameter to Transactional::flatMap makes you wish for a way to perform multiple operations at once without them depending directly on each other. For this use there is the Transactional::all method that supports performing multiple operations sequentially.

void transferFunds(UUID from, UUID to, BigDecimal amount) {
    Transactiona.all(
        recordTransaction(from, amount.negate()),
        recordTransaction(to, amount)
    ).get();
}

Most of the functionality relies on the TransactionProvider that is responsible for providing the transaction scope. There are two flavors of providers:

• Vanilla TransactionProvider offers TransactionProvider::runWithTransaction and TransactionProvider::runWithoutTransaction. This works well together with JOOQ's DSLContext::transactionResult.
• ThreadContextTransactionProvider can be used with contextual API that has the more common begin, commit and rollback methods working together with the context of the running thread.