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Using custom number of transactions in a method |
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With container-managed transaction beans, you are limited to a single transaction per method. You would like to group some important sections of code into a single method but use multiple transactions within the entire method. You need transaction control like this if you have a method that contains critical sections of code that cannot be broken into separate methods for CMT control.
This enables you to roll back a small section of code and exit the method without executing the remaining method. This applies only to session beans, because entity beans must always use container-managed transactions.
In order to enable custom transactions it is necessary change session bean to manage its own transactions by altering its XML descriptor, like in the sample below:
...
<session>
<ejb-name>SomeSession</ejb-name>
<home>SomeSessionHome</home>
<remote>SomeSession</remote>
<ejb-class>SomeSessionBean</ejb-class>
<session-type>Stateful</session-type>
<!-- enable bean-managed transactions: -->
<transaction-type>Bean</transaction-type>
</session>
...
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Here is bean method:
public void someMethod() {
UserTransaction transaction = null;
// the first transaction:
try {
transaction = ejbContext.getUserTransaction();
transaction.begin();
// perform code...
transaction.commit();
} catch (Exception e) {
//need to rollback?
if (transaction != null) {
transaction.rollback();
}
}
// the second transaction:
try {
transaction = ejbContext.getUserTransaction();
transaction.begin();
// perform code...
transaction.commit();
} catch (Exception e) {
//need to rollback?
if (transaction != null) {
transaction.rollback();
}
}
// and so on ...
}
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