Transaction¶
Doma supports local transaction. This document explains how to configure and use the local transaction.
If you want to use global transaction, use frameworks or application servers which support JTA (Java Transaction API).
See also Configuration definition .
Configuration¶
To use local transaction, these conditions are required:
- Return
LocalTransactionDataSource
fromgetDataSource
inConfig
- Generate
LocalTransactionManager
using theLocalTransactionDataSource
above in the constructor - Use the
LocalTransactionManager
above to control database access
There are several ways to generate and get the LocalTransactionManager
,
but the simplest way is to generate it in the constructor of Config
implementation class
and make the Config
implementation class singleton.
Here is an example:
public class DbConfig implements Config {
private static final DbConfig CONFIG = new DbConfig();
private final Dialect dialect;
private final LocalTransactionDataSource dataSource;
private final TransactionManager transactionManager;
private DbConfig() {
dialect = new H2Dialect();
dataSource = new LocalTransactionDataSource(
"jdbc:h2:mem:tutorial;DB_CLOSE_DELAY=-1", "sa", null);
transactionManager = new LocalTransactionManager(
dataSource.getLocalTransaction(getJdbcLogger()));
}
@Override
public Dialect getDialect() {
return dialect;
}
@Override
public DataSource getDataSource() {
return dataSource;
}
@Override
public TransactionManager getTransactionManager() {
return transactionManager;
}
public static DbConfig singleton() {
return CONFIG;
}
}
Usage¶
We use the following DAO interface in example code:
@Dao
public interface EmployeeDao {
@Sql("select /*%expand*/* from employee where id = /*id*/0")
@Select
Employee selectById(Integer id);
@Update
int update(Employee employee);
@Delete
int delete(Employee employee);
}
Start and finish transactions¶
You can start a transaction with one of following methods of TransactionManager
:
- required
- requiresNew
- notSupported
Use a lambda expression to write a process which you want to run in a transaction.
TransactionManager tm = DbConfig.singleton().getTransactionManager();
EmployeeDao dao = new EmployeeDaoImpl(DbConfig.singleton());
tm.required(() -> {
Employee employee = dao.selectById(1);
employee.setName("hoge");
employee.setJobType(JobType.PRESIDENT);
dao.update(employee);
});
The transaction is committed if the lambda expression finishes successfully. The transaction is rolled back if the lambda expression throws an exception.
Explicit rollback¶
Besides throwing an exception, you can use setRollbackOnly
method to rollback a transaction.
TransactionManager tm = DbConfig.singleton().getTransactionManager();
EmployeeDao dao = new EmployeeDaoImpl(DbConfig.singleton());
tm.required(() -> {
Employee employee = dao.selectById(1);
employee.setName("hoge");
employee.setJobType(JobType.PRESIDENT);
dao.update(employee);
// Mark as rollback
tm.setRollbackOnly();
});
Savepoint¶
With a savepoint, you can cancel specific changes in a transaction.
TransactionManager tm = DbConfig.singleton().getTransactionManager();
EmployeeDao dao = new EmployeeDaoImpl(DbConfig.singleton());
tm.required(() -> {
// Search and update
Employee employee = dao.selectById(1);
employee.setName("hoge");
dao.update(employee);
// Create a savepoint
tm.setSavepoint("beforeDelete");
// Delete
dao.delete(employee);
// Rollback to the savepoint (cancel the deletion above)
tm.rollback("beforeDelete");
});