Extended JTA support

Extended JTA support provides application programming interfaces additional to the UserTransaction interface that is defined in the JTA as part of the J2EE specification. Specifically, the API extensions provide the following functionality:

  • Access to global and local transaction identifiers associated with the thread.

    The global id is based on the tid in CosTransactions::PropagationContext: and the local id identifies the transaction uniquely within the local JVM.

  • A transaction synchronization callback that enables any J2EE component to register an interest in transaction completion.

    This can be used by advanced applications to flush updates before transaction completion and clear up state after transaction completion. J2EE (and related) specifications position this function generally as the domain of the J2EE containers.

An application uses a JNDI lookup of java:comp/websphere/ExtendedJTATransaction to get an ExtendedJTATransaction object, which it then uses as follows 

ExtendedJTATransaction exJTA = (ExtendedJTATransaction)ctx.lookup("
  java:comp/websphere/ExtendedJTATransaction");
SynchronizationCallback sync = new SynchronizationCallback();
exJTA.registerSynchronizationCallback(sync);

The ExtendedJTATransaction object supports the registration of one or more application-provided SynchronizationCallbacks. Depending on how the callback is registered, each registered callback is called at one of the following points:

  • At the end of every transaction that runs on the application server (whether the transaction is started locally or imported).

  • At the end of the transaction for which the callback was registered.

The following information provides an overview of the interfaces provided by the Extended JTA support. For more detailed information, see the Javadoc.

 

SynchronizationCallback interface

An object implementing this interface is enlisted once through the ExtendedJTATransaction interface, and receives notification of transaction completion.

Although an object implementing this interface can run in a J2EE server, there is no specific J2EE component active when this object is called. So, the object has limited direct access to any J2EE resources. Specifically, it has no access to the java: namespace or to any container-mediated resource. Such an object can cache a reference to a J2EE component (for example, a stateless session bean) that it delegates to. The object would then have all the normal access to J2EE resources and could be used, for example, to acquire a JDBC connection and flush updates to a database during beforeCompletion.

 

ExtendedJTATransaction interface

A WebSphere programming model extension to the J2EE JTA support. An object implementing this interface is bound, by WebSphere J2EE containers that support this interface, at java:comp/websphere/ExtendedJTATransaction. Access to this object, when called from an EJB container, is not restricted to component-managed transactions.

 

See Also


Global transactions

 

Related Information


Javadoc