docs/src/docs/asciidoc/programmaticTransactions.adoc

GORM's transaction management is built on Spring and uses Spring's Transaction abstraction for dealing with programmatic transactions.

However, GORM classes have been enhanced to make this simpler with the link:../api/org/grails/datastore/gorm/GormEntity.html#withTransaction(groovy.lang.Closure)[withTransaction(Closure)]  method. This method has a single parameter, a Closure, which has a single parameter which is a Spring https://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/transaction/TransactionStatus.html[TransactionStatus] instance.

==== Using the withTransaction Method

Here's an example of using `withTransaction` in a controller methods:

[source,java]
----
def transferFunds() {
    Account.withTransaction { status ->
        def source = Account.get(params.from)
        def dest = Account.get(params.to)

        def amount = params.amount.toInteger()
        if (source.active) {
            if (dest.active) {
                source.balance -= amount
                dest.amount += amount
            }
            else {
                status.setRollbackOnly()
            }
        }
    }
}
----

In this example we rollback the transaction if the destination account is not active. 

Also, if an `Exception` (both checked or runtime exception) or `Error` is thrown during the process the transaction will automatically be rolled back..

WARNING: GORM versions prior to 6.0.0 did not roll back transactions for a checked `Exception`.

You can also use "save points" to rollback a transaction to a particular point in time if you don't want to rollback the entire transaction. This can be achieved through the use of Spring's https://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/transaction/SavepointManager.html[SavePointManager] interface.

The `withTransaction` method deals with the begin/commit/rollback logic for you within the scope of the block.

==== Using TransactionService

Since GORM 6.1, if you need more flexibility then instead you can instead take advantage of the link:../api/grails/gorm/transactions/TransactionService.html[TransactionService], which can be obtained by looking it up from from the `HibernateDatastore`:

[source,groovy]
----
import grails.gorm.transactions.*

TransactionService transactionService = datastore.getService(TransactionService)
----

Or via dependency injection:

[source,groovy]
----
import grails.gorm.transactions.*

@Autowired TransactionService transactionService
----

Once you have an instance then there are various including `withTransaction`, `withRollback`, `withNewTransaction` etc. which helps with the construction of programmatic transactions.