Mule applies the concept of transactions to operations in application for which the result cannot remain indeterminate.  In other words, where a series of steps in a flow must succeed or fail as one unit, Mule uses a transaction to demarcate such a unit.  For example, you might use a transaction to encapsulate several steps in a flow for which the end result involves committing information to a database.  In this type of scenario, the commit is either entirely complete and succeeds, or is incomplete and it fails. Even if partially complete, the commit – or transaction – fails. Where a transaction fails, Mule rolls back the operations within the transaction so that no one part results in partial completion.

You can demarcate a transaction by applying a transaction to a connector. If a Mule flow begins with a transactional resource (such as an inbound connector), Mule can start a new transaction and manage the entire flow as a transaction. If your flow includes a transactional outbound connector, Mule manages the outgoing operation as a transaction. With both a transactional inbound and outbound connector, Mule executes the outgoing operation as part of the transaction initiated by the inbound connector.

The following connectors support transactional demarcation:

  • JMS

  • JDBC

  • VM

Note: As of Mule 3.5.0, the Database Connector replaces the JDBC connector, and the JDBC connector is deprecated. Applications that use the JDBC transport continue to work with the 3.5.0 Enterprise Runtime, but the connector is no longer available in the Studio palette to add to applications.

A Mule flow may begin with a non-transactional inbound connector – such as HTTP or SFTP – but which requires the use of a transaction within the flow. For example, a Mule flow may accept information from an external Web service,  then transform the data, before charging a credit card, and saving invoice information to a database. In such a situation, you can demarcate a transaction by wrapping the credit card charge and database commit operations within a transaction to ensure either complete success or complete failure and rollback.

For more information and full details about how to demarcate transactions in your Mule flow, refer to Transaction Management.