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Transaction
Overview
Komapper provides a High-level API for transaction management.
Note
When Komapper is combined with Spring Framework or Quarkus, this API works with the Spring Framework and Quarkus transaction managers.Transaction control
The API for transaction control provided by Komapper differs between the JDBC and R2DBC versions,
but the visual interface is unified.
The following explanation assumes that JdbcDatabase
or R2dbcDatabase
is declared with
the variable db
as shown below.
val db = JdbcDatabase("jdbc:h2:mem:example;DB_CLOSE_DELAY=-1")
val db = R2dbcDatabase("r2dbc:h2:mem:///example;DB_CLOSE_DELAY=-1")
Beginning and ending transactions
A transaction can be begun by calling the withTransaction
function:
db.withTransaction {
..
}
The withTransaction
function accepts a transaction attribute and a transaction property`:
db.withTransaction(
transactionAttribute = TransactionAttribute.REQUIRES_NEW,
transactionProperty = TransactionProperty.IsolationLevel.SERIALIZABLE) {
..
}
The transaction attribute can be one of the following two types:
- REQUIRED
- Support a current transaction; create a new one if none exists.
- REQUIRES_NEW
- Create a new transaction, suspending the current transaction if one exists.
The transaction property can contain various property elements:
- IsolationLevel
- Isolation level requested for the transaction.
- LockWaitTime
- Lock wait timeout.
- Name
- Name of the transaction.
- ReadOnly
- Whether the transaction should be started in read-only mode.
Multiple transaction property elements can be combined into a single transaction property with the +
operator:
val property = TransactionProperty.IsolationLevel.SERIALIZABLE + TransactionProperty.Name("myTx") + TransactionProperty.ReadOnly(true)
The transaction is committed or rolled back when the call to the withTransaction
function is finished.
The conditions for rollback are as follows:
- Call to the
withTransaction
function is terminated with an exception. - Explicit rollback is indicated in
withTransaction
function.
If the above rollback conditions are not met, the commit is performed.
Explicit rollback
If the setRollbackOnly
function is called, rollback is performed at the end of the withTransaction
function:
db.withTransaction { tx ->
..
tx.setRollbackOnly()
..
}
You can check if you have already called the setRollbackOnly
function with the isRollbackOnly
function:
db.withTransaction { tx ->
..
if (tx.isRollbackOnly()) {
..
}
..
}
Beginning and ending new transactions
To begin a new transaction when the current transaction exists, call the requiresNew
function.
db.withTransaction { tx ->
..
tx.requiresNew {
..
}
..
}
The requiresNew
function accepts a transaction property`:
db.withTransaction { tx ->
..
tx.requiresNew(transactionProperty = TransactionProperty.IsolationLevel.SERIALIZABLE) {
..
}
..
}
The transaction is committed or rolled back when the call to the requiresNew
function is finished.
The conditions for rollback are as follows:
- Call to the
requiresNew
function is terminated with an exception. - Explicit rollback is indicated in the
requiresNew
function.
If the above rollback conditions are not met, the commit is performed.
Transactional flows
Only R2dbcDatabase
provides the flowTransaction
function that constructs a transactional flow:
val db = R2dbcDatabase("r2dbc:h2:mem:///example;DB_CLOSE_DELAY=-1")
val transactionalFlow: Flow<Address> = db.flowTransaction {
val a = Meta.address
val address = db.runQuery {
QueryDsl.from(a).where { a.addressId eq 15 }.first()
}
db.runQuery {
QueryDsl.update(a).single(address.copy(street = "TOKYO"))
}
val addressFlow = db.flowQuery {
QueryDsl.from(a).orderBy(a.addressId)
}
emitAll(addressFlow)
}
// Transaction is executed
val list = transactionalFlow.toList()
In the above example, the call to the flowTransaction
function only constructs a flow.
The transaction is executed for the first time when the transactionalFlow
is collected.