Transactions

JTA

• unified interface independent of implementation

• specifies standard Java interface between transaction manager and parties involved in a distributed transaction system

UserTransaction

• Obtain

  • JNDI lookup: java:comp/UserTransaction

  • injection of UserTransaction object

Container-Managed Transactions (CMT) for EJB

Used in EJB (session or message-driven) with CMT, container sets boundaries of transactions.

If EJB uses CMT, it SHOULD NOT USE any transaction management methods that interfere with container's transaction, that includes:

• java.sql.Connection: commit, setAutoCommit, rollback

• javax.jms.Session - commit, rollback

• UserTransaction interface

Transaction attributes

To set, annotate class or method with javax.ejb.TransactionAttribute and set to one of javax.ejb.TransactionAttributeType.

If annotates the class, type is applied to all business methods.

Example: @TransactionAttribute(NOT_SUPPORTED)

Transaction attributes determines in what transaction (new? existing?) a method runs:

Transaction Rollback

• if a system exception is thrown, container automatically roll back

• invoke EJBContext.setRollbackOnly

• application exception does not cause automatic rollback

Synchronizing session bean's instance variables

SessionSynchronization interface allows stateful session bean instances to receive transaction synchronization notifications to synchronize instance variables. Container call interface methods

• afterBegin : immediately before invokes business method

• beforeCompletion : after finished business method, last opportunity for rollback

• afterCompletion : after completion of transaction, with parameter indicating whether transaction committed

Bean-Managed Transactions

When use application-managed (bean managed) transaction for (1) session bean or (2) message-driven bean, first to decide whether to use (1) Java Database Connectivity or (2) JTA transaction

JTA Transaction

• controlled by Java EE transaction manager

• independent of transaction manager implementation

• can span to multiple database from different vendors

• limitation: does not support nested transactions

• demarcation methods of javax.transaction.UserTransaction interface:

  • begin

  • commit

  • rollback

• for stateful session bean: retains transaction even each business method opens / closes connection

Business method and transaction

For stateless session bean: business method must commit or rollback a transaction before returning (bean can be reused)

For stateful session bean with JTA transaction: association of bean instance and transaction is retained across multiple calls; even if each business method opens and closes database connection, the association is retained until transaction completes.

For stateful session bean with JDBC transaction: the JDBC connection retains the association between bean instance and transaction. If connection is closed, association not retained.

Do not use:

EJBContext.getRollbackOnly / setRollbackOnly

Annotation Transaction implemented by CDI Interceptor

http://smokeandice.blogspot.com/2009/12/cdi-and-declarative-transactions.html